Use cases#

Pick the case closest to yours. Each says how to record, which root to use, and where to look.

A slow request on a server#

1. Record with JDK Mission Control, and send the request while recording.
2. Use the request entry point as the root, such as org.springframework.web.servlet.DispatcherServlet::doDispatch. See Common roots.
3. Find the slowest request with vbtm sessions rec.vbtm --sort dur, or in the flame chart.

Slow startup#

1. Add waitstart=60s to the agent, and use the startup method as the root, such as org.springframework.boot.SpringApplication::run.
2. Start the application. It waits at main() until you press Start recording in JDK Mission Control.
3. Follow the widest calls in the flame chart, or run vbtm hot rec.vbtm.

A slow test#

1. Record with the agent alone, set in Surefire's argLine or Gradle's jvmArgs. See Adding the agent.
2. Use org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor::execute as the root. Each test method becomes one session.
3. Find the slowest tests with vbtm sessions tests.vbtm --sort dur.

A batch job#

1. Record with the agent alone, set in JAVA_TOOL_OPTIONS.
2. Use the job's entry method as the root.
3. Find where the time went with vbtm hot job.vbtm.

Let an AI agent find the cause#

Record in any of the ways above, add the vbtm skill to your agent, and ask why it was slow.