Open source continuously profiles Java processes running on the local Linux OS using async-profiler.


To use the component you must run Alloy as root and inside host PID namespace.


alloy "LABEL" {
  targets    = TARGET_LIST
  forward_to = RECEIVER_LIST


The following arguments are supported:

targetslist(map(string))List of java process targets to profile.yes
forward_tolist(ProfilesReceiver)List of receivers to send collected profiles to.yes
tmp_dirstringTemporary directory to store async-profiler./tmpno

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, 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.


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


The asprof binary runs with root permissions. If you change the tmp_dir configuration to something other than /tmp, then you must ensure that the directory is only writable by root.

targets argument

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 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.


The following blocks are supported inside the definition of

profiling_configprofiling_configDescribes java profiling

profiling_config block

The profiling_config block describes how async-profiler is invoked.

The following arguments are supported:

intervaldurationHow frequently to collect profiles from the targets.“60s”no
cpuboolA flag to enable cpu profiling, using itimer async-profiler event.trueno
sample_rateintCPU profiling sample rate. It is converted from Hz to interval and passed as -i arg to async-profiler.100no
allocstringAllocation profiling sampling configuration It is passed as --alloc arg to async-profiler.“512k”no
lockstringLock profiling sampling configuration. It is passed as --lock arg to async-profiler.“10ms”no

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

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

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

Debug information doesn’t expose any component-specific debug information.

Debug metrics doesn’t expose any component-specific debug metrics.


Profile every java process on the current host

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

Compatible components can accept arguments from the following components:


Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.