Add 99th percentile

Author: nicktindall

server/src/main/java/org/elasticsearch/common/util/concurrent/TaskExecutionTimeTrackingEsThreadPoolExecutor.java

@@ -35,7 +35,7 @@
  */
 public final class TaskExecutionTimeTrackingEsThreadPoolExecutor extends EsThreadPoolExecutor {
 
-    private static final int[] LATENCY_PERCENTILES_TO_REPORT = { 50, 90 };
+    private static final int[] LATENCY_PERCENTILES_TO_REPORT = { 50, 90, 99 };
     public static final String THREAD_POOL_METRIC_NAME_QUEUE_TIME = ".threads.queue.latency.histogram";
 
     private final Function<Runnable, WrappedRunnable> runnableWrapper;

server/src/test/java/org/elasticsearch/common/util/concurrent/TaskExecutionTimeTrackingEsThreadPoolExecutorTests.java

@@ -206,8 +206,9 @@ public void testQueueLatencyMetrics() {
                     ThreadPool.THREAD_POOL_METRIC_PREFIX + threadPoolName
                         + TaskExecutionTimeTrackingEsThreadPoolExecutor.THREAD_POOL_METRIC_NAME_QUEUE_TIME
                 );
-            assertThat(measurements, hasSize(2));
+            assertThat(measurements, hasSize(3));
             // we have to use greater than or equal to because the actual delay might be higher than what we imposed
+            assertThat(getPercentile(measurements, "99"), greaterThanOrEqualTo(expectedHistogram.getPercentile(0.99f)));
             assertThat(getPercentile(measurements, "90"), greaterThanOrEqualTo(expectedHistogram.getPercentile(0.9f)));
             assertThat(getPercentile(measurements, "50"), greaterThanOrEqualTo(expectedHistogram.getPercentile(0.5f)));
         } finally {