[GitHub] milleruntime commented on a change in pull request #399: ACCUMULO-4847 Fix Retry utility's API

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

milleruntime commented on a change in pull request #399: ACCUMULO-4847 Fix Retry utility's API
URL: https://github.com/apache/accumulo/pull/399#discussion_r174558134
 
 

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 File path: fate/src/main/java/org/apache/accumulo/fate/util/Retry.java
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 @@ -0,0 +1,356 @@
+/*
+ * 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.
+ */
+package org.apache.accumulo.fate.util;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.NANOSECONDS;
+
+import java.util.concurrent.TimeUnit;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
+
+/**
+ * Encapsulates the retrying implementation for some operation. Provides bounded retry attempts with a bounded, linear backoff.
+ */
+public class Retry {
+  private static final Logger log = LoggerFactory.getLogger(Retry.class);
+
+  private long maxRetries; // not final for testing
+  private long waitIncrement; // not final for testing
+  private long maxWait; // not final for testing
+  private final long logIntervalNanoSec;
+
+  private long retriesDone;
+  private long currentWait;
+
+  private boolean hasNeverLogged;
+  private long lastRetryLog;
+
+  /**
+   * @param maxRetries
+   *          Maximum times to retry or MAX_RETRY_DISABLED if no maximum
+   * @param startWait
+   *          The amount of time (ms) to wait for the initial retry
+   * @param maxWait
+   *          The maximum wait (ms)
+   * @param waitIncrement
+   *          The amount of time (ms) to increment next wait time by
+   * @param logInterval
+   *          The amount of time (ms) between logging retries
+   */
+  private Retry(long maxRetries, long startWait, long waitIncrement, long maxWait, long logInterval) {
+    this.maxRetries = maxRetries;
+    this.maxWait = maxWait;
+    this.waitIncrement = waitIncrement;
+    this.retriesDone = 0;
+    this.currentWait = startWait;
+    this.logIntervalNanoSec = MILLISECONDS.toNanos(logInterval);
+    this.hasNeverLogged = true;
+    this.lastRetryLog = -1;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  long getMaxRetries() {
+    return maxRetries;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  long getCurrentWait() {
+    return currentWait;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  long getWaitIncrement() {
+    return waitIncrement;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  long getMaxWait() {
+    return maxWait;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  void setMaxRetries(long maxRetries) {
+    this.maxRetries = maxRetries;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  void setStartWait(long startWait) {
+    this.currentWait = startWait;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  void setWaitIncrement(long waitIncrement) {
+    this.waitIncrement = waitIncrement;
+  }
+
+  // Visible for testing
+  @VisibleForTesting
+  void setMaxWait(long maxWait) {
+    this.maxWait = maxWait;
+  }
+
+  public boolean hasInfiniteRetries() {
+    return maxRetries < 0;
+  }
+
+  public long getLogInterval() {
+    return NANOSECONDS.toMillis(logIntervalNanoSec);
+  }
+
+  public boolean canRetry() {
+    return hasInfiniteRetries() || (retriesDone < maxRetries);
+  }
+
+  public void useRetry() {
+    if (!canRetry()) {
+      throw new IllegalStateException("No retries left");
+    }
+
+    retriesDone++;
+  }
+
+  public boolean hasRetried() {
+    return retriesDone > 0;
+  }
+
+  public long retriesCompleted() {
+    return retriesDone;
+  }
+
+  public void waitForNextAttempt() throws InterruptedException {
+    log.debug("Sleeping for {}ms before retrying operation", currentWait);
+    sleep(currentWait);
+    currentWait = Math.min(maxWait, currentWait + waitIncrement);
+  }
+
+  protected void sleep(long wait) throws InterruptedException {
+    Thread.sleep(wait);
+  }
+
+  public void logRetry(Logger log, String message, Throwable t) {
+    // log the first time as debug, and then after every logInterval as a warning
+    long now = System.nanoTime();
+    if (lastRetryLog < 0) {
+      if (log.isDebugEnabled()) {
+        log.debug(getMessage(message, t));
+      }
+      lastRetryLog = now;
+    } else if ((now - lastRetryLog) > logIntervalNanoSec) {
+      log.warn(getMessage(message), t);
+      lastRetryLog = now;
+    } else {
+      if (log.isTraceEnabled()) {
+        log.trace(getMessage(message, t));
+      }
+    }
+  }
+
+  public void logRetry(Logger log, String message) {
+    // log the first time as debug, and then after every logInterval as a warning
+    long now = System.nanoTime();
+    if (hasNeverLogged) {
+      if (log.isDebugEnabled()) {
+        log.debug(getMessage(message));
+      }
+      hasNeverLogged = false;
+      lastRetryLog = now;
+    } else if ((now - lastRetryLog) > logIntervalNanoSec) {
+      log.warn(getMessage(message));
+      lastRetryLog = now;
+    } else {
+      if (log.isTraceEnabled()) {
+        log.trace(getMessage(message));
+      }
+    }
+  }
+
+  private String getMessage(String message) {
+    return message + ", retrying attempt " + (retriesDone + 1) + " (suppressing retry messages for " + getLogInterval() + "ms)";
+  }
+
+  private String getMessage(String message, Throwable t) {
+    return message + ":" + t + ", retrying attempt " + (retriesDone + 1) + " (suppressing retry messages for " + getLogInterval() + "ms)";
+  }
+
+  public interface NeedsRetries {
+    /**
+     * @return this builder with the maximum number of retries set to unlimited
+     */
+    NeedsRetryDelay infiniteRetries();
+
+    /**
+     * @param max
+     *          the maximum number of retries to set
+     * @return this builder with the maximum number of retries set to the provided value
+     */
+    NeedsRetryDelay maxRetries(long max);
+  }
+
+  public interface NeedsRetryDelay {
+    /**
+     * @param duration
+     *          the amount of time to wait before the first retry; input is converted to milliseconds, rounded down to the nearest
+     * @return this builder with the initial wait period set
+     */
+    NeedsTimeIncrement retryAfter(long duration, TimeUnit unit);
+  }
+
+  public interface NeedsTimeIncrement {
+    /**
+     * @param duration
+     *          the amount of additional time to add before each subsequent retry; input is converted to milliseconds, rounded down to the nearest
+     * @return this builder with the increment amount set
+     */
+    NeedsMaxWait incrementBy(long duration, TimeUnit unit);
+  }
+
+  public interface NeedsMaxWait {
+    /**
+     * @param duration
+     *          the maximum amount of time to which the waiting period between retries can be incremented; input is converted to milliseconds, rounded down to
+     *          the nearest
+     * @return this builder with a maximum time limit set
+     */
+    NeedsLogInterval maxWait(long duration, TimeUnit unit);
+  }
+
+  public interface NeedsLogInterval {
+    /**
+     * @param duration
+     *          the minimum time interval between logging that a retry is occurring; input is converted to milliseconds, rounded down to the nearest
+     * @return this builder with a logging interval set
+     */
+    BuilderDone logInterval(long duration, TimeUnit unit);
+  }
+
+  public interface BuilderDone {
+    /**
+     * Create a RetryFactory from this builder which can be used to create many Retry objects with the same settings.
+     *
+     * @return this builder as a factory; intermediate references to this builder cannot be used to change options after this has been called
+     */
+    RetryFactory createFactory();
+
+    /**
+     * Create a single Retry object with the currently configured builder settings.
+     *
+     * @return a retry object from this builder's settings
+     */
+    Retry createRetry();
+  }
+
+  public interface RetryFactory {
+    /**
+     * Create a single Retry object from this factory's settings.
+     *
+     * @return a retry object from this factory's settings
+     */
+    Retry createRetry();
+  }
+
+  public static NeedsRetries builder() {
+    return new RetryFactoryBuilder();
+  }
+
+  private static class RetryFactoryBuilder implements NeedsRetries, NeedsRetryDelay, NeedsTimeIncrement, NeedsMaxWait, NeedsLogInterval, BuilderDone,
 
 Review comment:
   Since you changed to the builder pattern why not rename to "RetryBuilder".  I think its confusing to intermingle the terms.

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