[GitHub] [beam] damccorm commented on a diff in pull request #23978: Add basic counter support to the typescript SDK.

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

damccorm commented on code in PR #23978:
URL: https://github.com/apache/beam/pull/23978#discussion_r1013984800


##########
sdks/typescript/src/apache_beam/worker/metrics.ts:
##########
@@ -0,0 +1,288 @@
+/*
+ * 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.
+ */
+
+import * as protobufjs from "protobufjs";
+
+import { MonitoringInfo } from "../proto/metrics";
+import { Coder, Context } from "../coders/coders";
+import { IterableCoder } from "../coders/required_coders";
+import { VarIntCoder } from "../coders/standard_coders";
+
+export interface MetricSpec {
+  metricType: string;
+  name: string;
+}
+
+const metricTypes = new Map<
+  string,
+  (spec: MetricSpec) => MetricCell<unknown>
+>();
+
+/**
+ * A MetricCell holds the concrete value of a metric at runtime.
+ *
+ * Different types of metrics will have different types of MetricCells,
+ * with the relationship being stored in the metricTypes map.
+ */
+interface MetricCell<T> {
+  // This is the publicly available function at execution time.
+  update: (value: T) => void;
+
+  // Rather than clear and re-create counters every time, we reset them
+  // between bundles.
+  reset: () => void;
+
+  // These are used to pass counters back from the worker.
+  toEmptyMonitoringInfo: () => MonitoringInfo;
+  payload: () => Uint8Array;
+
+  // These are used for reading counters.
+  loadFromPayload: (paylaod: Uint8Array) => void;
+  merge(other: MetricCell<T>);
+  extract(): any;
+}
+
+class Counter implements MetricCell<number> {
+  private value = 0;
+
+  constructor(spec: MetricSpec) {}
+
+  update(value: number) {
+    this.value += value;
+  }
+
+  reset(): void {
+    this.value = 0;
+  }
+
+  toEmptyMonitoringInfo(): MonitoringInfo {
+    return MonitoringInfo.create({
+      urn: "beam:metric:user:sum_int64:v1",
+      type: "beam:metrics:sum_int64:v1",
+    });
+  }
+
+  payload(): Uint8Array {
+    return encode(this.value, new VarIntCoder());
+  }
+
+  loadFromPayload(payload: Uint8Array) {
+    this.value = decode(payload, new VarIntCoder());
+  }
+
+  merge(other) {
+    this.value += other.value;
+  }
+
+  extract() {
+    return this.value;
+  }
+}
+
+metricTypes.set("beam:metric:user:sum_int64:v1", (spec) => new Counter(spec));
+
+class Distribution implements MetricCell<number> {
+  private count = 0;
+  private sum = 0;
+  private min = 0;
+  private max = 0;
+
+  private coder = new IterableCoder(new VarIntCoder());
+
+  constructor(spec: MetricSpec) {}
+
+  update(value: number) {
+    if (this.count == 0) {
+      this.count = 1;
+      this.sum = this.min = this.max = value;
+    } else {
+      this.count += 1;
+      this.sum += value;
+      this.min = Math.min(value, this.min);
+      this.max = Math.max(value, this.max);
+    }
+  }
+
+  reset(): void {
+    this.count = 0;

Review Comment:
   Should we be resetting the rest of the metrics here? I know functionally that they'll be reset on the first update, but this might lead to weird/unexpected behavior if any operation is done with an unupdated metric.
   
   I guess maybe a better question is: is it ever valid to do anything with a metric that hasn't been updated at least once? If so, things like merge won't ever really work and we'd be better off initializing min to MAX_INT, max to MIN_INT, and fully resetting them here.



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