Skip to content

Latest commit

 

History

History
72 lines (60 loc) · 3.29 KB

README.md

File metadata and controls

72 lines (60 loc) · 3.29 KB

Helidon Labs Incubator - Metrics for Virtual Threads

Starting in Java 24, a new management bean VirtualThreadSchedulerMXBean makes some statistics related to virtual threads available programmatically.

This Helidon Labs incubating component is a library which, when added as a dependency to a Helidon application, exposes several new Helidon built-in meters in the base scope derived from the values from VirtualThreadSchedulerMXBean.

This component works with Helidon 4.x applications, but only if you build and run this library and your application with Java 24.

Build and use the component

Build the library:

Make sure to use JDK 24 or the build will fail.

mvn clean install

Modify the app to use the component

Edit your project's pom.xml file to add a dependency on this component:

<dependency>
    <groupId>io.helidon.labs.incubator</groupId>
    <artifactId>helidon-labs-incubator-virtual-threads-metrics</artifactId>
    <version>1.0.0-SNAPSHOT</version>
</dependency>

For example, you can add the above dependency to your application or to the Helidon SE QuickStart or Helidon MP QuickStart application. Make sure to use JDK 24 to build the app.

Build and start the app

Build and start the server using JDK 24:

mvn package
java -jar target/whatever-app-you-build.jar

Retrieve metrics

The metrics endpoint is different for SE and MP apps.

For SE:

curl http://localhost:8080/observe/metrics -H "Accept: application/json" | jq | grep vthread

The preceding command uses jq to format the retrieved JSON. You do not need it but it formats its output nicely for ease of reading and searching.

Output:

    "vthreads.scheduler.pool-size": 1,
    "vthreads.scheduler.queued-virtual-thread-count": 0,
    "vthreads.scheduler.parallelism": 8,
    "vthreads.scheduler.mounted-virtual-thread-count": 1,

For MP:

curl http://localhost:8080/metrics | grep vthread

Output:

# HELP vthreads_scheduler_mounted_virtual_thread_count Estimate of the number of virtual threads that are currently mounted by the scheduler; -1 if not known.
# TYPE vthreads_scheduler_mounted_virtual_thread_count gauge
vthreads_scheduler_mounted_virtual_thread_count{mp_scope="base",} 1.0
# HELP vthreads_scheduler_queued_virtual_thread_count Estimate of the number of virtual threads that are queued to the scheduler to start or continue execution; -1 if not known.
# TYPE vthreads_scheduler_queued_virtual_thread_count gauge
vthreads_scheduler_queued_virtual_thread_count{mp_scope="base",} 0.0
# HELP vthreads_scheduler_parallelism Scheduler's target parallelism.
# TYPE vthreads_scheduler_parallelism gauge
vthreads_scheduler_parallelism{mp_scope="base",} 8.0
# HELP vthreads_scheduler_pool_size Current number of platform threads that the scheduler has started but have not terminated; -1 if not known.
# TYPE vthreads_scheduler_pool_size gauge
vthreads_scheduler_pool_size{mp_scope="base",} 1.0