ZOOKEEPER-4951: Optimize the default Prometheus max queue size (apache#2278)

Author: Li Wang <[email protected]>

Reviewer: kezhuw <[email protected]>

Author: li4wang

zookeeper-docs/src/main/resources/markdown/zookeeperAdmin.md

@@ -2279,7 +2279,7 @@ options are used to configure the [AdminServer](#sc_adminserver).
 * *metricsProvider.maxQueueSize* :
    **New in 3.7.1:**
    The max queue size for Prometheus summary metrics reporting task.
-   Default value is 1000000.
+   Default value is 10000.
 
 * *metricsProvider.workerShutdownTimeoutMs* :
    **New in 3.7.1:**

zookeeper-metrics-providers/zookeeper-prometheus-metrics/src/main/java/org/apache/zookeeper/metrics/prometheus/PrometheusMetricsProvider.java

@@ -84,7 +84,7 @@ public class PrometheusMetricsProvider implements MetricsProvider {
 
     /**
      * The max queue size for Prometheus summary metrics reporting task.
-     * Default value is 1000000.
+     * Default value is 10000.
      */
     static final String MAX_QUEUE_SIZE = "maxQueueSize";
 
@@ -111,7 +111,7 @@ public class PrometheusMetricsProvider implements MetricsProvider {
     private final MetricsServletImpl servlet = new MetricsServletImpl();
     private final Context rootContext = new Context();
     private int numWorkerThreads = 1;
-    private int maxQueueSize = 1000000;
+    private int maxQueueSize = 10000;
     private long workerShutdownTimeoutMs = 1000;
     private Optional<ExecutorService> executorOptional = Optional.empty();
 
@@ -161,7 +161,7 @@ public void configure(Properties configuration) throws MetricsProviderLifeCycleE
         this.numWorkerThreads = Integer.parseInt(
                 configuration.getProperty(NUM_WORKER_THREADS, "1"));
         this.maxQueueSize = Integer.parseInt(
-                configuration.getProperty(MAX_QUEUE_SIZE, "1000000"));
+                configuration.getProperty(MAX_QUEUE_SIZE, "10000"));
         this.workerShutdownTimeoutMs = Long.parseLong(
                 configuration.getProperty(WORKER_SHUTDOWN_TIMEOUT_MS, "1000"));
     }