[GitHub] [beam] KonradJanica commented on a change in pull request #16985: [BEAM-13925] Add ability to get metrics on pr-bot performance

[GitBox <gi...@apache.org>]

KonradJanica commented on a change in pull request #16985:
URL: https://github.com/apache/beam/pull/16985#discussion_r818927401



##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(

Review comment:
       I believe the outter `new Date` constructor is not needed.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;

Review comment:
       Perhaps use [find](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find) to save some lines.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}

Review comment:
       Could we use [split](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/split) here instead? E.g. body.split(' @').

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {

Review comment:
       ditto `forEach` => `of`

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {
+    firstTimeContribution: checkIfFirstTimeContributor(pull, pullsFromLastYear),
+    timeToFirstReview: getTimeToFirstReview(
+      pull,
+      comments,
+      reviews,
+      creationDate,
+      mergedDate
+    ),
+    timeFromCreationToCompletion: mergedDate.getTime() - creationDate.getTime(),
+    timeFromReviewersMentionedToCompletion:
+      getTimeFromReviewerMentionedToCompletion(
+        pull,
+        comments,
+        reviewComments,
+        mergedDate
+      ),
+    mergedDate: mergedDate,
+  };
+
+  return prStats;
+}
+
+function getMetricBucketStartDate(pullStat: PrStats, bucketEnd: Date): number {
+  let bucketStart = bucketEnd;
+  while (bucketStart.getTime() > pullStat.mergedDate.getTime()) {
+    bucketStart.setDate(bucketStart.getDate() - 7);
+  }
+
+  return bucketStart.getTime();
+}
+
+function distinctReviewers(pullStats: PrStats[]): string[] {
+  let users: Set<string> = new Set();
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (user) => {
+        users.add(user);
+      }
+    );
+  });
+  return Array.from(users);
+}
+
+async function committersFromReviewers(users: string[]): Promise<string[]> {
+  let committers: string[] = [];
+  for (let i = 0; i < users.length; i++) {
+    let user = users[i];
+    if (await github.checkIfCommitter(user)) {
+      committers.push(user);
+    }
+  }
+  return committers;
+}

Review comment:
       All loops in this block will be cleaner using the `for (const foo of bar)` syntax.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {
+    firstTimeContribution: checkIfFirstTimeContributor(pull, pullsFromLastYear),
+    timeToFirstReview: getTimeToFirstReview(
+      pull,
+      comments,
+      reviews,
+      creationDate,
+      mergedDate
+    ),
+    timeFromCreationToCompletion: mergedDate.getTime() - creationDate.getTime(),
+    timeFromReviewersMentionedToCompletion:
+      getTimeFromReviewerMentionedToCompletion(
+        pull,
+        comments,
+        reviewComments,
+        mergedDate
+      ),
+    mergedDate: mergedDate,
+  };
+
+  return prStats;
+}
+
+function getMetricBucketStartDate(pullStat: PrStats, bucketEnd: Date): number {
+  let bucketStart = bucketEnd;
+  while (bucketStart.getTime() > pullStat.mergedDate.getTime()) {
+    bucketStart.setDate(bucketStart.getDate() - 7);
+  }
+
+  return bucketStart.getTime();
+}
+
+function distinctReviewers(pullStats: PrStats[]): string[] {
+  let users: Set<string> = new Set();
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (user) => {
+        users.add(user);
+      }
+    );
+  });
+  return Array.from(users);
+}
+
+async function committersFromReviewers(users: string[]): Promise<string[]> {
+  let committers: string[] = [];
+  for (let i = 0; i < users.length; i++) {
+    let user = users[i];
+    if (await github.checkIfCommitter(user)) {
+      committers.push(user);
+    }
+  }
+  return committers;
+}
+
+function averageTimeFromCommitterAssignmentToPrMerge(
+  pullStats: PrStats[],
+  committers: string[]
+): number {
+  if (committers.length === 0) {
+    return 0;
+  }
+  let numCommitterReviews = 0;
+  let totalTimeFromAssignToMerge = 0;
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          numCommitterReviews++;
+          totalTimeFromAssignToMerge +=
+            pullStat.timeFromReviewersMentionedToCompletion[reviewer];
+        }
+      }
+    );
+  });
+  return totalTimeFromAssignToMerge / numCommitterReviews;
+}
+
+// Calculates a gini index of inequality for reviews.
+// 0 is perfectly equally distributed, 1 is inequally distributed (with 1 person having all reviews)
+function getGiniIndexForCommitterReviews(
+  pullStats: PrStats[],
+  committers: string[]
+) {
+  let reviewsPerCommitter: { [key: string]: number } = {};
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          if (reviewer in reviewsPerCommitter) {
+            reviewsPerCommitter[reviewer]++;
+          } else {
+            reviewsPerCommitter[reviewer] = 1;
+          }

Review comment:
       Perhaps a ternary statement is cleaner here.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};

Review comment:
       Perhaps a [map](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) would be more readable.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);

Review comment:
       all these `let` => `const`.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {

Review comment:
       `for (const comment of comments)` syntax is preferred over forEach.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}

Review comment:
       Perhaps using [some](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some), but reversing the condition, would be cleaner.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;

Review comment:
       `++retries;`

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {

Review comment:
       This will never be true.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {
+    firstTimeContribution: checkIfFirstTimeContributor(pull, pullsFromLastYear),
+    timeToFirstReview: getTimeToFirstReview(
+      pull,
+      comments,
+      reviews,
+      creationDate,
+      mergedDate
+    ),
+    timeFromCreationToCompletion: mergedDate.getTime() - creationDate.getTime(),
+    timeFromReviewersMentionedToCompletion:
+      getTimeFromReviewerMentionedToCompletion(
+        pull,
+        comments,
+        reviewComments,
+        mergedDate
+      ),
+    mergedDate: mergedDate,
+  };
+
+  return prStats;
+}
+
+function getMetricBucketStartDate(pullStat: PrStats, bucketEnd: Date): number {
+  let bucketStart = bucketEnd;

Review comment:
       `let` => `const`.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;

Review comment:
       `++page;`

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {

Review comment:
       `let` => `const`

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;

Review comment:
       Are the outer brackets necessary?

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {
+    firstTimeContribution: checkIfFirstTimeContributor(pull, pullsFromLastYear),
+    timeToFirstReview: getTimeToFirstReview(
+      pull,
+      comments,
+      reviews,
+      creationDate,
+      mergedDate
+    ),
+    timeFromCreationToCompletion: mergedDate.getTime() - creationDate.getTime(),
+    timeFromReviewersMentionedToCompletion:
+      getTimeFromReviewerMentionedToCompletion(
+        pull,
+        comments,
+        reviewComments,
+        mergedDate
+      ),
+    mergedDate: mergedDate,
+  };
+
+  return prStats;
+}
+
+function getMetricBucketStartDate(pullStat: PrStats, bucketEnd: Date): number {
+  let bucketStart = bucketEnd;
+  while (bucketStart.getTime() > pullStat.mergedDate.getTime()) {
+    bucketStart.setDate(bucketStart.getDate() - 7);
+  }
+
+  return bucketStart.getTime();
+}
+
+function distinctReviewers(pullStats: PrStats[]): string[] {
+  let users: Set<string> = new Set();
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (user) => {
+        users.add(user);
+      }
+    );
+  });
+  return Array.from(users);
+}
+
+async function committersFromReviewers(users: string[]): Promise<string[]> {
+  let committers: string[] = [];
+  for (let i = 0; i < users.length; i++) {
+    let user = users[i];
+    if (await github.checkIfCommitter(user)) {
+      committers.push(user);
+    }
+  }
+  return committers;
+}
+
+function averageTimeFromCommitterAssignmentToPrMerge(
+  pullStats: PrStats[],
+  committers: string[]
+): number {
+  if (committers.length === 0) {
+    return 0;
+  }
+  let numCommitterReviews = 0;
+  let totalTimeFromAssignToMerge = 0;
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          numCommitterReviews++;
+          totalTimeFromAssignToMerge +=
+            pullStat.timeFromReviewersMentionedToCompletion[reviewer];
+        }
+      }
+    );
+  });
+  return totalTimeFromAssignToMerge / numCommitterReviews;

Review comment:
       If committers is not empty but pullState.timeFromReviewersMentionedToCompletion is empty, `numCommitterReviews` could be 0 resulting in `NaN`.

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {
+    firstTimeContribution: checkIfFirstTimeContributor(pull, pullsFromLastYear),
+    timeToFirstReview: getTimeToFirstReview(
+      pull,
+      comments,
+      reviews,
+      creationDate,
+      mergedDate
+    ),
+    timeFromCreationToCompletion: mergedDate.getTime() - creationDate.getTime(),
+    timeFromReviewersMentionedToCompletion:
+      getTimeFromReviewerMentionedToCompletion(
+        pull,
+        comments,
+        reviewComments,
+        mergedDate
+      ),
+    mergedDate: mergedDate,
+  };
+
+  return prStats;
+}
+
+function getMetricBucketStartDate(pullStat: PrStats, bucketEnd: Date): number {
+  let bucketStart = bucketEnd;
+  while (bucketStart.getTime() > pullStat.mergedDate.getTime()) {
+    bucketStart.setDate(bucketStart.getDate() - 7);
+  }
+
+  return bucketStart.getTime();
+}
+
+function distinctReviewers(pullStats: PrStats[]): string[] {
+  let users: Set<string> = new Set();
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (user) => {
+        users.add(user);
+      }
+    );
+  });
+  return Array.from(users);
+}
+
+async function committersFromReviewers(users: string[]): Promise<string[]> {
+  let committers: string[] = [];
+  for (let i = 0; i < users.length; i++) {
+    let user = users[i];
+    if (await github.checkIfCommitter(user)) {
+      committers.push(user);
+    }
+  }
+  return committers;
+}
+
+function averageTimeFromCommitterAssignmentToPrMerge(
+  pullStats: PrStats[],
+  committers: string[]
+): number {
+  if (committers.length === 0) {
+    return 0;
+  }
+  let numCommitterReviews = 0;
+  let totalTimeFromAssignToMerge = 0;
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          numCommitterReviews++;
+          totalTimeFromAssignToMerge +=
+            pullStat.timeFromReviewersMentionedToCompletion[reviewer];
+        }
+      }
+    );
+  });
+  return totalTimeFromAssignToMerge / numCommitterReviews;
+}
+
+// Calculates a gini index of inequality for reviews.
+// 0 is perfectly equally distributed, 1 is inequally distributed (with 1 person having all reviews)
+function getGiniIndexForCommitterReviews(
+  pullStats: PrStats[],
+  committers: string[]
+) {
+  let reviewsPerCommitter: { [key: string]: number } = {};
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          if (reviewer in reviewsPerCommitter) {
+            reviewsPerCommitter[reviewer]++;
+          } else {
+            reviewsPerCommitter[reviewer] = 1;
+          }
+        }
+      }
+    );
+  });
+  let reviewCounts = Object.values(reviewsPerCommitter);
+  reviewCounts.sort();
+  let giniNumerator = 0;
+  let giniDenominator = 0;
+  const n = reviewCounts.length;
+  for (let i = 1; i <= reviewCounts.length; i++) {
+    let yi = reviewCounts[i - 1];
+    giniNumerator += (n + 1 - i) * yi;
+    giniDenominator += yi;
+  }
+  return (1 / n) * (n + 1 - (2 * giniNumerator) / giniDenominator);
+}
+
+async function aggregateStatsForBucket(
+  pullStats: PrStats[]
+): Promise<AggregatedMetrics> {
+  const reviewers = distinctReviewers(pullStats);
+  const committers = await committersFromReviewers(reviewers);
+  const firstTimePrs = pullStats.filter(
+    (pullStat) => pullStat.firstTimeContribution
+  );
+  let averageTimeToNewContributorFirstReview = 0;
+  if (firstTimePrs.length > 0) {
+    averageTimeToNewContributorFirstReview =
+      firstTimePrs.reduce(
+        (sumTime, prStat) => sumTime + prStat.timeToFirstReview,
+        0
+      ) / firstTimePrs.length;
+  }
+  return {
+    prsCompleted: pullStats.length,
+    prsCompletedByNewContributors: firstTimePrs.length,
+    averageTimeToFirstReview:
+      pullStats.reduce(
+        (sumTime, prStat) => sumTime + prStat.timeToFirstReview,
+        0
+      ) / pullStats.length,
+    averageTimeToNewContributorFirstReview:
+      averageTimeToNewContributorFirstReview,
+    averageTimeCreationToCompletion:
+      pullStats.reduce(
+        (sumTime, prStat) => sumTime + prStat.timeFromCreationToCompletion,
+        0
+      ) / pullStats.length,
+    numUsersPerformingReviews: reviewers.length,
+    numCommittersPerformingReviews: committers.length,
+    numNonCommittersPerformingReviews: reviewers.length - committers.length,
+    giniIndexCommittersPerformingReviews: getGiniIndexForCommitterReviews(
+      pullStats,
+      committers
+    ),
+    averageTimeFromCommitterAssignmentToPrMerge:
+      averageTimeFromCommitterAssignmentToPrMerge(pullStats, committers),
+  };
+}
+
+function convertMsToRoundedMinutes(milliseconds: number): number {
+  return Math.floor(milliseconds / 60000);

Review comment:
       `60000` => `60_000`

##########
File path: scripts/ci/pr-bot/gatherMetrics.ts
##########
@@ -0,0 +1,527 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const fs = require("fs");
+const github = require("./shared/githubUtils");
+const {
+  REPO_OWNER,
+  REPO,
+  PATH_TO_METRICS_CSV,
+  BOT_NAME,
+} = require("./shared/constants");
+
+interface PrStats {
+  firstTimeContribution: boolean;
+  timeToFirstReview: number;
+  timeFromCreationToCompletion: number;
+  timeFromReviewersMentionedToCompletion: { [key: string]: number };
+  mergedDate: Date;
+}
+
+interface AggregatedMetrics {
+  prsCompleted: number;
+  prsCompletedByNewContributors: number;
+  averageTimeToFirstReview: number;
+  averageTimeToNewContributorFirstReview: number;
+  averageTimeCreationToCompletion: number;
+  numUsersPerformingReviews: number;
+  numCommittersPerformingReviews: number;
+  numNonCommittersPerformingReviews: number;
+  giniIndexCommittersPerformingReviews: number;
+  averageTimeFromCommitterAssignmentToPrMerge: number;
+}
+
+async function getCompletedPullsFromLastYear(): Promise<any[]> {
+  const cutoffDate = new Date(
+    new Date().setFullYear(new Date().getFullYear() - 1)
+  );
+  console.log(`Getting PRs newer than ${cutoffDate}`);
+  const githubClient = github.getGitHubClient();
+  let result = await githubClient.rest.pulls.list({
+    owner: REPO_OWNER,
+    repo: REPO,
+    state: "closed",
+    per_page: 100, // max allowed
+  });
+  let page = 2;
+  let retries = 0;
+  let pulls = result.data;
+  while (
+    result.data.length > 0 &&
+    new Date(result.data[result.data.length - 1].created_at) > cutoffDate
+  ) {
+    if (retries === 0) {
+      console.log(`Getting PRs, page: ${page}`);
+      console.log(
+        `Current oldest PR = ${new Date(
+          result.data[result.data.length - 1].created_at
+        )}`
+      );
+    }
+    try {
+      result = await githubClient.rest.pulls.list({
+        owner: REPO_OWNER,
+        repo: REPO,
+        state: "closed",
+        per_page: 100, // max allowed
+        page: page,
+      });
+      pulls = pulls.concat(result.data);
+      page += 1;
+      retries = 0;
+    } catch (err) {
+      if (retries >= 3) {
+        throw err;
+      }
+      retries += 1;
+    }
+  }
+  console.log("Got all PRs, moving to the processing stage");
+  return pulls;
+}
+
+// Rather than check the whole repo history (expensive),
+// we'll just look at the last year's worth of contributions to check if they're a first time contributor.
+// If they contributed > 1 year ago, their experience is probably similar to a first time contributor anyways.
+function checkIfFirstTimeContributor(
+  pull: any,
+  pullsFromLastYear: any[]
+): boolean {
+  for (const pullFromLastYear of pullsFromLastYear) {
+    if (
+      pullFromLastYear.created_at < pull.created_at &&
+      pullFromLastYear.user.login === pull.user.login
+    ) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Get time between pr creation and the first comment, approval, or merge that isn't done by:
+// (a) the author
+// (b) automated tooling
+function getTimeToFirstReview(
+  pull: any,
+  comments: any[],
+  reviews: any[],
+  creationDate: Date,
+  mergedDate: Date
+): number {
+  let timeToFirstReview = mergedDate.getTime() - creationDate.getTime();
+  let i = 0;
+  while (i < reviews.length && reviews[i].user.login === pull.user.login) {
+    i++;
+  }
+  if (i < reviews.length) {
+    const firstReviewDate = new Date(reviews[i].submitted_at);
+    timeToFirstReview = Math.min(
+      timeToFirstReview,
+      firstReviewDate.getTime() - creationDate.getTime()
+    );
+  }
+  for (const comment of comments) {
+    if (
+      comment.user.login != pull.user.login &&
+      comment.user.login != BOT_NAME
+    ) {
+      let commentTime = new Date(comment.created_at);
+      timeToFirstReview = Math.min(
+        timeToFirstReview,
+        commentTime.getTime() - creationDate.getTime()
+      );
+    }
+  }
+  return timeToFirstReview;
+}
+
+// Takes a R: @reviewer comment and extracts all reviewers tagged
+// Returns an empty list if no reviewer can be extracted
+function extractReviewersTaggedFromCommentBody(body: string): string[] {
+  if (!body) {
+    return [];
+  }
+  body = body.toLowerCase();
+  if (body.indexOf("r: @") < -1) {
+    return [];
+  }
+  let usernames: string[] = [];
+  let usernameIndex = 0;
+  while (body.indexOf(" @", usernameIndex) > -1) {
+    usernameIndex = body.indexOf(" @", usernameIndex) + 2;
+    let curUsername = "";
+    while (
+      usernameIndex < body.length &&
+      body[usernameIndex].match(/^[0-9a-z]+$/)
+    ) {
+      curUsername += body[usernameIndex];
+      usernameIndex += 1;
+    }
+    // Filter out username from PR template
+    if (curUsername && curUsername != "username") {
+      usernames.push(curUsername);
+    }
+  }
+  return usernames;
+}
+
+// Returns a dictionary mapping reviewers to the amount of time from their first comment to pr completion.
+function getTimeFromReviewerMentionedToCompletion(
+  pull: any,
+  comments: any[],
+  reviewComments: any[],
+  mergedDate: Date
+): { [key: string]: number } {
+  comments = comments.concat(reviewComments);
+  comments.push(pull);
+  let timeToCompletionPerReviewer = {};
+  comments.forEach((comment) => {
+    let reviewersTagged = extractReviewersTaggedFromCommentBody(comment.body);
+    let commentCreationDate = new Date(comment.created_at);
+    let timeToCompletion = mergedDate.getTime() - commentCreationDate.getTime();
+    reviewersTagged.forEach((reviewer) => {
+      if (reviewer in timeToCompletionPerReviewer) {
+        timeToCompletionPerReviewer[reviewer] = Math.max(
+          timeToCompletion,
+          timeToCompletionPerReviewer[reviewer]
+        );
+      } else {
+        timeToCompletionPerReviewer[reviewer] = timeToCompletion;
+      }
+    });
+  });
+
+  return timeToCompletionPerReviewer;
+}
+
+async function extractPrStats(
+  pull: any,
+  pullsFromLastYear: any[]
+): Promise<PrStats> {
+  const githubClient = github.getGitHubClient();
+  const creationDate = new Date(pull.created_at);
+  const mergedDate = new Date(pull.merged_at);
+  const reviews = (
+    await githubClient.rest.pulls.listReviews({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  // GitHub has a concept of review comments (must be part of a review) and issue comments on a repo, so we need to look at both
+  const comments = (
+    await githubClient.rest.issues.listComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      issue_number: pull.number,
+    })
+  ).data;
+  const reviewComments = (
+    await githubClient.rest.pulls.listReviewComments({
+      owner: REPO_OWNER,
+      repo: REPO,
+      pull_number: pull.number,
+    })
+  ).data;
+  let prStats: PrStats = {
+    firstTimeContribution: checkIfFirstTimeContributor(pull, pullsFromLastYear),
+    timeToFirstReview: getTimeToFirstReview(
+      pull,
+      comments,
+      reviews,
+      creationDate,
+      mergedDate
+    ),
+    timeFromCreationToCompletion: mergedDate.getTime() - creationDate.getTime(),
+    timeFromReviewersMentionedToCompletion:
+      getTimeFromReviewerMentionedToCompletion(
+        pull,
+        comments,
+        reviewComments,
+        mergedDate
+      ),
+    mergedDate: mergedDate,
+  };
+
+  return prStats;
+}
+
+function getMetricBucketStartDate(pullStat: PrStats, bucketEnd: Date): number {
+  let bucketStart = bucketEnd;
+  while (bucketStart.getTime() > pullStat.mergedDate.getTime()) {
+    bucketStart.setDate(bucketStart.getDate() - 7);
+  }
+
+  return bucketStart.getTime();
+}
+
+function distinctReviewers(pullStats: PrStats[]): string[] {
+  let users: Set<string> = new Set();
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (user) => {
+        users.add(user);
+      }
+    );
+  });
+  return Array.from(users);
+}
+
+async function committersFromReviewers(users: string[]): Promise<string[]> {
+  let committers: string[] = [];
+  for (let i = 0; i < users.length; i++) {
+    let user = users[i];
+    if (await github.checkIfCommitter(user)) {
+      committers.push(user);
+    }
+  }
+  return committers;
+}
+
+function averageTimeFromCommitterAssignmentToPrMerge(
+  pullStats: PrStats[],
+  committers: string[]
+): number {
+  if (committers.length === 0) {
+    return 0;
+  }
+  let numCommitterReviews = 0;
+  let totalTimeFromAssignToMerge = 0;
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          numCommitterReviews++;
+          totalTimeFromAssignToMerge +=
+            pullStat.timeFromReviewersMentionedToCompletion[reviewer];
+        }
+      }
+    );
+  });
+  return totalTimeFromAssignToMerge / numCommitterReviews;
+}
+
+// Calculates a gini index of inequality for reviews.
+// 0 is perfectly equally distributed, 1 is inequally distributed (with 1 person having all reviews)
+function getGiniIndexForCommitterReviews(
+  pullStats: PrStats[],
+  committers: string[]
+) {
+  let reviewsPerCommitter: { [key: string]: number } = {};
+  pullStats.forEach((pullStat) => {
+    Object.keys(pullStat.timeFromReviewersMentionedToCompletion).forEach(
+      (reviewer) => {
+        if (committers.indexOf(reviewer) > -1) {
+          if (reviewer in reviewsPerCommitter) {
+            reviewsPerCommitter[reviewer]++;
+          } else {
+            reviewsPerCommitter[reviewer] = 1;
+          }
+        }
+      }
+    );
+  });
+  let reviewCounts = Object.values(reviewsPerCommitter);
+  reviewCounts.sort();
+  let giniNumerator = 0;
+  let giniDenominator = 0;
+  const n = reviewCounts.length;
+  for (let i = 1; i <= reviewCounts.length; i++) {
+    let yi = reviewCounts[i - 1];
+    giniNumerator += (n + 1 - i) * yi;
+    giniDenominator += yi;
+  }
+  return (1 / n) * (n + 1 - (2 * giniNumerator) / giniDenominator);
+}
+
+async function aggregateStatsForBucket(
+  pullStats: PrStats[]
+): Promise<AggregatedMetrics> {
+  const reviewers = distinctReviewers(pullStats);
+  const committers = await committersFromReviewers(reviewers);
+  const firstTimePrs = pullStats.filter(
+    (pullStat) => pullStat.firstTimeContribution
+  );
+  let averageTimeToNewContributorFirstReview = 0;
+  if (firstTimePrs.length > 0) {
+    averageTimeToNewContributorFirstReview =
+      firstTimePrs.reduce(
+        (sumTime, prStat) => sumTime + prStat.timeToFirstReview,
+        0
+      ) / firstTimePrs.length;
+  }
+  return {
+    prsCompleted: pullStats.length,
+    prsCompletedByNewContributors: firstTimePrs.length,
+    averageTimeToFirstReview:
+      pullStats.reduce(
+        (sumTime, prStat) => sumTime + prStat.timeToFirstReview,
+        0
+      ) / pullStats.length,
+    averageTimeToNewContributorFirstReview:
+      averageTimeToNewContributorFirstReview,
+    averageTimeCreationToCompletion:
+      pullStats.reduce(
+        (sumTime, prStat) => sumTime + prStat.timeFromCreationToCompletion,
+        0
+      ) / pullStats.length,
+    numUsersPerformingReviews: reviewers.length,
+    numCommittersPerformingReviews: committers.length,
+    numNonCommittersPerformingReviews: reviewers.length - committers.length,
+    giniIndexCommittersPerformingReviews: getGiniIndexForCommitterReviews(
+      pullStats,
+      committers
+    ),
+    averageTimeFromCommitterAssignmentToPrMerge:
+      averageTimeFromCommitterAssignmentToPrMerge(pullStats, committers),
+  };
+}
+
+function convertMsToRoundedMinutes(milliseconds: number): number {
+  return Math.floor(milliseconds / 60000);
+}
+
+async function reportMetrics(statBuckets: { [key: number]: PrStats[] }) {
+  console.log("---------------------------------");
+  console.log("PR Stats");
+  console.log("---------------------------------");
+  let csvOutput = "";
+  csvOutput +=
+    "Bucket start (bucketed by merge time),PRs Completed,PRs completed by first time contributors,Average time in minutes to first review,Average time in minutes to first review for new contributors,Average time in minutes from PR creation to completion,Total number of reviewers,Total number of committers performing reviews,Total number of non-committers performing reviews,Gini index (fairness) of committers performing reviews,Average time in minutes from committer assignment to PR merge";
+  const startDates = Object.keys(statBuckets);
+  for (let i = 0; i < startDates.length; i++) {
+    let startDate = startDates[i];
+    let aggregatedStats = await aggregateStatsForBucket(statBuckets[startDate]);
+    console.log();
+
+    const bucketStart = new Date(parseInt(startDate));
+    console.log("Bucket start:", bucketStart);
+    csvOutput += `\n${bucketStart.toDateString()}`;
+
+    console.log("PRs completed:", aggregatedStats.prsCompleted);
+    csvOutput += `,${aggregatedStats.prsCompleted}`;
+
+    console.log(
+      "PRs completed by first time contributors:",
+      aggregatedStats.prsCompletedByNewContributors
+    );
+    csvOutput += `,${aggregatedStats.prsCompletedByNewContributors}`;
+
+    console.log(
+      "Average time in minutes to first review:",
+      convertMsToRoundedMinutes(aggregatedStats.averageTimeToFirstReview)
+    );
+    csvOutput += `,${convertMsToRoundedMinutes(
+      aggregatedStats.averageTimeToFirstReview
+    )}`;
+
+    console.log(
+      "Average time in minutes to first review for new contributors:",
+      convertMsToRoundedMinutes(
+        aggregatedStats.averageTimeToNewContributorFirstReview
+      )
+    );
+    csvOutput += `,${convertMsToRoundedMinutes(
+      aggregatedStats.averageTimeToNewContributorFirstReview
+    )}`;
+
+    console.log(
+      "Average time in minutes from PR creation to completion:",
+      convertMsToRoundedMinutes(aggregatedStats.averageTimeCreationToCompletion)
+    );
+    csvOutput += `,${convertMsToRoundedMinutes(
+      aggregatedStats.averageTimeCreationToCompletion
+    )}`;
+
+    console.log(
+      "Total number of reviewers:",
+      aggregatedStats.numUsersPerformingReviews
+    );
+    csvOutput += `,${aggregatedStats.numUsersPerformingReviews}`;
+
+    console.log(
+      "Total number of committers performing reviews:",
+      aggregatedStats.numCommittersPerformingReviews
+    );
+    csvOutput += `,${aggregatedStats.numCommittersPerformingReviews}`;
+
+    console.log(
+      "Total number of non-committers performing reviews:",
+      aggregatedStats.numNonCommittersPerformingReviews
+    );
+    csvOutput += `,${aggregatedStats.numNonCommittersPerformingReviews}`;
+
+    console.log(
+      "Gini index (fairness) of committers performing reviews:",
+      aggregatedStats.giniIndexCommittersPerformingReviews
+    );
+    csvOutput += `,${aggregatedStats.giniIndexCommittersPerformingReviews}`;
+
+    console.log(
+      "Average time in minutes from committer assignment to PR merge:",
+      convertMsToRoundedMinutes(
+        aggregatedStats.averageTimeFromCommitterAssignmentToPrMerge
+      )
+    );
+    csvOutput += `,${convertMsToRoundedMinutes(
+      aggregatedStats.averageTimeFromCommitterAssignmentToPrMerge
+    )}`;
+  }
+  fs.writeFileSync(PATH_TO_METRICS_CSV, csvOutput);
+  console.log(`Output written to ${PATH_TO_METRICS_CSV}`);
+}
+
+async function gatherMetrics() {
+  // We will only aggregate metrics from the last 90 days,
+  // but will look further back to determine if this is a user's first contribution
+  const pullsFromLastYear = await getCompletedPullsFromLastYear();
+  let cutoffDate = new Date();
+  cutoffDate.setDate(cutoffDate.getDate() - 90);
+
+  let pullStats: PrStats[] = [];
+  console.log("Extracting stats from pulls - this may take a while");
+  for (let i = 0; i < pullsFromLastYear.length; i++) {
+    let pull = pullsFromLastYear[i];
+    if (new Date(pull.created_at) > cutoffDate && pull.merged_at) {
+      pullStats.push(await extractPrStats(pull, pullsFromLastYear));
+    }
+    if (i % 10 === 0) {
+      process.stdout.write(".");
+    }
+  }
+
+  console.log("\nDone extracting stats, formatting results");
+
+  let statBuckets: { [key: number]: PrStats[] } = {};
+  let bucketEnd = new Date();
+  bucketEnd.setUTCHours(23, 59, 59, 999);
+  pullStats.forEach((pullStat) => {
+    let bucketStart = getMetricBucketStartDate(pullStat, bucketEnd);
+    if (bucketStart in statBuckets) {
+      statBuckets[bucketStart].push(pullStat);
+    } else {
+      statBuckets[bucketStart] = [pullStat];
+    }
+  });
+  await reportMetrics(statBuckets);
+}
+
+gatherMetrics();
+
+export {};

Review comment:
       I'm not familiar with this self executing export pattern. This pattern could make it difficult to debug when an import causes a side-effect. I think it's better to call `gatherMetrics` from the running class.




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