HBASE-24658 Update PolicyBasedChaosMonkey to handle uncaught exceptions

Running `ServerKillingChaosMonkey` via `RESTApiClusterManager` for any
duration of time slowly leaks region servers. I see failures on the
RESTApi side go unreported on the ChaosMonkey side. It seems like
`RuntimeException`s are being thrown and lost.

`PolicyBasedChaosMonkey` uses a primitive means of thread management
anyway. Update to use a thread pool, thread groups, and an
uncaughtExceptionHandler.

Signed-off-by: Bharath Vissapragada <[email protected]>
Signed-off-by: Viraj Jasani <[email protected]>

hbase-it/src/test/java/org/apache/hadoop/hbase/chaos/monkies/PolicyBasedChaosMonkey.java

@@ -1,4 +1,4 @@
-/**
+/*
  * 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
@@ -18,11 +18,16 @@
 
 package org.apache.hadoop.hbase.chaos.monkies;
 
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 
+import java.util.Objects;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import org.apache.commons.lang.math.RandomUtils;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -37,28 +42,44 @@ public class PolicyBasedChaosMonkey extends ChaosMonkey {
 
   private static final Log LOG = LogFactory.getLog(PolicyBasedChaosMonkey.class);
   private static final long ONE_SEC = 1000;
-  private static final long FIVE_SEC = 5 * ONE_SEC;
   private static final long ONE_MIN = 60 * ONE_SEC;
 
   public static final long TIMEOUT = ONE_MIN;
 
   final IntegrationTestingUtility util;
 
+  private final Policy[] policies;
+  private final ExecutorService monkeyThreadPool;
+
   /**
    * Construct a new ChaosMonkey
    * @param util the HBaseIntegrationTestingUtility already configured
    * @param policies custom policies to use
    */
-  public PolicyBasedChaosMonkey(IntegrationTestingUtility util, Policy... policies) {
-    this.util = util;
-    this.policies = policies;
+  public PolicyBasedChaosMonkey(IntegrationTestingUtility util, Collection<Policy> policies) {
+    this(util, policies.toArray(new Policy[0]));
   }
 
-  public PolicyBasedChaosMonkey(IntegrationTestingUtility util, Collection<Policy> policies) {
-    this.util = util;
-    this.policies = policies.toArray(new Policy[policies.size()]);
+  public PolicyBasedChaosMonkey(IntegrationTestingUtility util, Policy... policies) {
+    this.util = Objects.requireNonNull(util);
+    this.policies = Objects.requireNonNull(policies);
+    if (policies.length == 0) {
+      throw new IllegalArgumentException("policies may not be empty");
+    }
+    this.monkeyThreadPool = buildMonkeyThreadPool(policies.length);
   }
 
+  private static ExecutorService buildMonkeyThreadPool(final int size) {
+    return Executors.newFixedThreadPool(size, new ThreadFactoryBuilder()
+      .setDaemon(false)
+      .setNameFormat("ChaosMonkey-%d")
+      .setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
+        @Override public void uncaughtException(Thread t, Throwable e) {
+          throw new RuntimeException(e);
+        }
+      })
+      .build());
+  }
 
   /** Selects a random item from the given items */
   public static <T> T selectRandomItem(T[] items) {
@@ -99,50 +120,33 @@ public static <T> List<T> selectRandomItems(T[] items, float ratio) {
     return originalItems.subList(startIndex, startIndex + selectedNumber);
   }
 
-  private Policy[] policies;
-  private Thread[] monkeyThreads;
-
   @Override
   public void start() throws Exception {
-    monkeyThreads = new Thread[policies.length];
-
-    for (int i=0; i<policies.length; i++) {
-      policies[i].init(new Policy.PolicyContext(this.util));
-      Thread monkeyThread = new Thread(policies[i], "ChaosMonkeyThread");
-      monkeyThread.start();
-      monkeyThreads[i] = monkeyThread;
+    final Policy.PolicyContext context = new Policy.PolicyContext(this.util);
+    for (final Policy policy : policies) {
+      policy.init(context);
+      monkeyThreadPool.execute(policy);
     }
   }
 
   @Override
   public void stop(String why) {
-    if (policies == null) {
-      return;
-    }
-
+    // stop accepting new work (shouldn't be any with a fixed-size pool)
+    monkeyThreadPool.shutdown();
+    // notify all executing policies that it's time to halt.
     for (Policy policy : policies) {
       policy.stop(why);
     }
   }
 
   @Override
   public boolean isStopped() {
-    return policies[0].isStopped();
+    return monkeyThreadPool.isTerminated();
   }
 
-  /**
-   * Wait for ChaosMonkey to stop.
-   * @throws InterruptedException
-   */
   @Override
   public void waitForStop() throws InterruptedException {
-    if (monkeyThreads == null) {
-      return;
-    }
-    for (Thread monkeyThread : monkeyThreads) {
-      // TODO: bound the wait time per policy
-      monkeyThread.join();
-    }
+    monkeyThreadPool.awaitTermination(1, TimeUnit.MINUTES);
   }
 
   @Override