Documentation Grafana Alloy Reference Components pyroscope pyroscope.java

pyroscope.java

pyroscope.java continuously profiles Java processes running on the local Linux OS using async-profiler.

Usage

Alloy Copy

pyroscope.java "<LABEL>" {
  targets    = <TARGET_LIST>
  forward_to = <RECEIVER_LIST>
}

Target JVM configuration

When you use pyroscope.java to profile Java applications, you can configure the target JVMs with some command line flags that ensure accurate profiling, especially for inlined methods. Add the following flags to your Java application’s startup command:

java Copy

-XX:+UnlockDiagnosticVMOptions -XX:+DebugNonSafepoints

For more details, refer to Restrictions/Limitations in the async-profiler documentation.

Additional configuration for Linux capabilities

If your Kubernetes environment has Linux capabilities enabled, configure the following in your Helm values to ensure pyroscope.java functions properly:

YAML Copy

alloy:
  securityContext:
    runAsUser: 0
    runAsNonRoot: false
    capabilities:
      add:
        - PERFMON
        - SYS_PTRACE
        - SYS_RESOURCE
        - SYS_ADMIN

These capabilities enable Alloy to access performance monitoring subsystems, trace processes, override resource limits, and perform necessary system administration tasks for profiling.

Arguments

You can use the following arguments with pyroscope.java:

Profiling behavior

The special label __process_pid__ must always be present in each target of targets and corresponds to the PID of the process to profile.

After component startup, pyroscope.java creates a temporary directory under tmp_dir and extracts the async-profiler binaries for both glibc and musl into the directory with the following layout.

text Copy

/tmp/alloy-asprof-glibc-{SHA1}/bin/asprof
/tmp/alloy-asprof-glibc-{SHA1}/lib/libasyncProfiler.so
/tmp/alloy-asprof-musl-{SHA1}/bin/asprof
/tmp/alloy-asprof-musl-{SHA1}/lib/libasyncProfiler.so

After process profiling startup, the component detects libc type and copies according libAsyncProfiler.so into the target process file system at the exact same path.

targets

The special __process_pid__ label must always be present and corresponds to the process PID that’s used for profiling.

Labels starting with a double underscore (__) are treated as internal, and are removed prior to scraping.

The special label service_name is required and must always be present. If it’s not specified, pyroscope.scrape will attempt to infer it from either of the following sources, in this order:

1. __meta_kubernetes_pod_annotation_pyroscope_io_service_name which is a pyroscope.io/service_name Pod annotation.
2. __meta_kubernetes_namespace and __meta_kubernetes_pod_container_name
3. __meta_docker_container_name
4. __meta_dockerswarm_container_label_service_name or __meta_dockerswarm_service_name

If service_name isn’t specified and couldn’t be inferred, then it’s set to unspecified.

Blocks

You can use the following block with pyroscope.java:

profiling_config

The profiling_config block describes how async-profiler is invoked.

The following arguments are supported:

Refer to profiler-options for more information about async-profiler configuration.

event

The event argument configures the profiling mode used by async-profiler. async-profiler supports various profiling modes including CPU profiling, wall-clock profiling, and hardware performance monitoring events. For a complete overview of all available profiling modes and their use cases, refer to Profiling modes in the async-profiler documentation.

per_thread

custom_arguments

custom_arguments passes async-profiler start flags directly.

When custom_arguments is set, Alloy skips these options from this block:

cpu, event, per_thread, sample_rate, alloc, lock, log_level.

For example, this enables multi-event profiling (cpu, alloc, and lock) with custom thresholds:

Alloy Copy

pyroscope.java "java" {
  targets    = discovery.relabel.java.output
  forward_to = [pyroscope.write.staging.receiver]

  profiling_config {
    interval = "60s"
    custom_arguments = ["-e", "cpu,alloc,lock", "--alloc", "2m", "--lock", "10ms"]
  }
}

Refer to Profiling modes and profiler-options for the complete async-profiler option list.

Exported fields

pyroscope.java doesn’t export any fields that can be referenced by other components.

Component health

pyroscope.java is only reported as unhealthy when given an invalid configuration. In those cases, exported fields retain their last healthy values.

Debug information

pyroscope.java doesn’t expose any component-specific debug information.

Debug metrics

pyroscope.java doesn’t expose any component-specific debug metrics.

Examples

Profile every java process on the current host

Alloy Copy

pyroscope.write "staging" {
  endpoint {
    url = "http://localhost:4040"
  }
}

discovery.process "all" {
  refresh_interval = "60s"
  discover_config {
    cwd = true
    exe = true
    commandline = true
    username = true
    uid = true
    container_id = true
  }
}

discovery.relabel "java" {
  targets = discovery.process.all.targets
  rule {
    action = "keep"
    regex = ".*/java$"
    source_labels = ["__meta_process_exe"]
  }
}

pyroscope.java "java" {
  targets = discovery.relabel.java.output
  forward_to = [pyroscope.write.staging.receiver]
  profiling_config {
    interval = "60s"
    alloc = "512k"
    cpu = true
    sample_rate = 100
    lock = "1ms"
  }
}

Compatible components

pyroscope.java can accept arguments from the following components:

• Components that export Targets
• Components that export Pyroscope ProfilesReceiver