Using an Async Profiler to create a flame-graph

Owned by Florian Raschbichler
Last updated: Mar 25, 2024 by Mikhail Chernyakov
2 min read

Install

(For Java11at least version 1.5 is needed) Download Async Profiler from: https://github.com/jvm-profiling-tools/async-profiler

wget https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.7.1/async-profiler-1.7.1-linux-x64.tar.gz mkdir /opt/async-profiler tar xvzf async-profiler-*-linux-x64.tar.gz -C /opt/async-profiler

 Since Kernel 4.6 the following commands must be executed as root on the system to enable profiling

echo 1 > /proc/sys/kernel/perf_event_paranoid echo 0 > /proc/sys/kernel/kptr_restrict

Usage

Find the HiveMQ process id (must be user root or user hivemq)

#Java Process ID Tool jps #or #ps with filter for only pid and only processes by user hivemq ps -u hivemq -o pid= #or #always works ps aux | grep hivemq

Run profiler.sh (-d is the duration of the recording in seconds)

You need to make sure that all async-pofiler files belong to the same user that is running the HiveMQ process and that you start the profiler.sh script as that user.

Quick command (can be run as root, only works if hivemq is the only process running for user `hivemq`)

Async Profiler 2.0

SVG format is no longer supported since 2.0. Use HTML instead.

In the terraform-testing

When terraform-testing is used

Kubernetes / Docker

As usual, container platforms have some paranoid settings that are read-only. On the up side, we can leverage the fact that HiveMQ is always PID 1 in containers (unless shared namespaces are used in K8s):

Here's an idempotent block you can simply execute to generate a flamegraph in a container:

Then use kubectl cp or docker cp to copy the graph from the container.

systemd

Alternative: When using systemd, you can simply use 

Using async profiler in the systemd unit (start with HiveMQ):