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    Application Real-Time Monitoring Service:Thread pool and connection pool monitoring

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    Application Real-Time Monitoring Service:Thread pool and connection pool monitoring

    Last Updated:Apr 30, 2026

    The thread pool and connection pool monitoring feature lets you monitor key metrics for your application's thread pools and connection pools. These metrics include the core thread count, current thread count, maximum thread count, active thread count, and task queue size.

    Prerequisites

    Connect your application to Application Monitoring.

    Important

    The thread pool and connection pool monitoring feature is available only in the Pro Edition of Application Monitoring.

    Enable thread pool and connection pool monitoring

    Agent versions earlier than 2.7.1.3 do not support thread pool and connection pool monitoring. You must upgrade the agent to version 2.7.1.3 or later. For more information, see Upgrade the ARMS agent.

    • Thread pool and connection pool monitoring is enabled by default for agent versions 2.7.3.5 and later.

    • For agent versions from 2.7.1.3 to 2.7.3.4, perform the following steps to manually enable the feature.

    1. Log on to the ARMS console. In the left-side navigation pane, choose Application Monitoring > Application List.

    2. At the top of the Application List page, select a region, and then click the name of your target application.

      Note

      The icons in the Language column have the following meanings:

      Java图标: Java applications connected to Application Monitoring.

      image: Go applications connected to Application Monitoring.

      image: Python applications connected to Application Monitoring.

      -: Represents an application connected to Managed Service for OpenTelemetry.

    3. In the left-side navigation pane, click Application Settings.

    4. On the Custom Configuration tab, in the Pooled Monitoring Configuration section, turn on the Thread pool, connection pool monitoring switch.

    View thread pool and connection pool metrics

    After you enable this feature, view the monitoring metrics on the Application Details page, under the Thread Pool Monitoring and Connection Pool Monitoring tabs.

    Figure 1. Thread pool monitoring线程池监控

    Figure 2. Connection pool monitoring连接池监控

    Supported frameworks for thread pools

    Agent versions 4.1.x and later

    Supported frameworks:

    • java.util.ThreadPoolExecutor: Typically used for Tomcat 8 to 9.1, Dubbo, HSF, Vert.x, and user-defined thread pools.

    • org.apache.tomcat.util.threads.ThreadPoolExecutor: Typically used for Tomcat 9.1 and later.

    • org.eclipse.jetty.util.thread.QueuedThreadPool: Typically used for Jetty.

    • org.xnio.XnioWorker: Typically used for Undertow.

    The following metrics are collected:

    Metric name

    Supported framework

    Description

    arms_thread_pool_core_pool_size

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    • XnioWorker

    • QueuedThreadPool

    The core thread count. This is a static configuration and does not typically change.

    arms_thread_pool_max_pool_size

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    • XnioWorker

    • QueuedThreadPool

    The maximum thread count. This is a static configuration and does not typically change.

    arms_thread_pool_active_thread_count

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    • XnioWorker

    • QueuedThreadPool

    The number of threads currently executing tasks.

    arms_thread_pool_current_thread_count

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    • QueuedThreadPool

    The current thread count, which includes both active threads and idle threads that are waiting for tasks.

    arms_thread_pool_max_thread_count

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    The highest recorded number of threads in the thread pool.

    arms_thread_pool_scheduled_task_count

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    The total number of tasks that have been scheduled for execution.

    arms_thread_pool_completed_task_count

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    The total number of tasks that have completed execution.

    arms_thread_pool_rejected_task_count

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    • QueuedThreadPool

    The total number of tasks rejected by the thread pool.

    arms_thread_pool_queue_size

    • ThreadPoolExecutor (JDK)

    • ThreadPoolExecutor (Tomcat 9.1+)

    • XnioWorker

    • QueuedThreadPool

    The current number of tasks waiting in the queue.

    Agent versions earlier than 4.1.x

    Thread pool monitoring supports Tomcat, HSF, Dubbo, Vert.x, and Undertow frameworks. For Undertow, agent versions 3.1.x and earlier support Undertow 1.x to 2.0.x, while agent versions 3.2.x and later support all versions of Undertow.

    The following metrics are collected:

    Metric name

    Metric

    Core thread count

    arms_threadpool_core_size

    Maximum thread count

    arms_threadpool_max_size

    Active thread count

    arms_threadpool_active_size

    Queue size

    arms_threadpool_queue_size

    Current thread count

    arms_threadpool_current_size

    For the SchedulerX framework, the following metric is collected:

    Metric name

    Metric

    Active thread count

    arms_threadpool_active_size

    Supported frameworks for connection pools

    Agent versions 4.1.x and later

    Supported frameworks: DBCP (>2.0), Vibur DBCP (>11.0), c3p0 (>0.9.2), Druid, HikariCP (>3.0), Jedis (>3.0), Lettuce (>5.0), Redisson (>3.0), tomcat-dbcp (>8.0), and tomcat-jdbc (>8.0).

    The following metrics are collected:

    Metric name

    Supported framework

    Description

    arms_connection_pool_connection_count

    DBCP, c3p0, Vibur DBCP, Druid, HikariCP, Jedis, Lettuce, Redisson, tomcat-dbcp, tomcat-jdbc

    The connection count. You can distinguish between active and idle connections by state.

    arms_connection_pool_connection_min_idle_count

    DBCP, Jedis, Druid, HikariCP, Lettuce, tomcat-dbcp, tomcat-jdbc

    The minimum number of idle connections. This is a static configuration and does not typically change.

    arms_connection_pool_connection_max_idle_count

    DBCP, Jedis, Druid, Lettuce, tomcat-dbcp, tomcat-jdbc

    The maximum number of idle connections. This is a static configuration and does not typically change.

    arms_connection_pool_connection_max_count

    DBCP, Druid, Vibur DBCP, HikariCP, tomcat-dbcp, tomcat-jdbc

    The maximum connection count. This is a static configuration and does not typically change.

    arms_connection_pool_pending_request_count

    c3p0, HikariCP, Jedis, tomcat-dbcp, tomcat-jdbc

    The number of pending connection requests.

    Agent versions earlier than 4.1.x

    For OkHttp2 and OkHttp3, the following metrics are collected:

    Metric name

    Metric

    Active connection count

    arms_threadpool_active_size

    Current connection count

    arms_threadpool_current_size

    For Apache HttpClient, the following metrics are collected:

    Metric name

    Metric

    Current connection count

    arms_threadpool_current_size

    Maximum connection count

    arms_threadpool_max_size

    Waiting queue size

    arms_threadpool_queue_size

    For Druid, the following metrics are collected:

    Metric name

    Metric

    Active connection count

    arms_threadpool_active_size

    Maximum connection count

    arms_threadpool_max_size

    For HikariCP, the following metrics are collected:

    Metric name

    Metric

    Active connection count

    arms_threadpool_active_size

    Maximum connection count

    arms_threadpool_max_size