Generate Flame Graphs with FE Profiler

Introduction

In Apache Doris 2.1.4 and later, the FE deployment directory ${DORIS_FE_HOME}/bin ships with a profile_fe.sh script. The script uses async-profiler to generate a flame graph of the FE so you can locate FE performance bottlenecks.

System Support

System	Supported
Linux	Yes
macOS	Yes
Windows	Not yet

Usage Steps

1. Run profile_fe.sh

# Profile the FE for 10 seconds by default and generate a flame graph
${DORIS_FE_HOME}/bin/profile_fe.sh

# Profile the FE for 30 seconds and generate a flame graph
PROFILE_SECONDS=30 ${DORIS_FE_HOME}/bin/profile_fe.sh

Environment Variable	Meaning	Default
PROFILE_SECONDS	async-profiler sampling duration (seconds)	10

2. Trigger the Workload

After you run the command, async-profiler keeps sampling for the specified duration. During this period, send the target queries repeatedly to the FE so that async-profiler can capture stack frames along the target code paths.

3. View the Flame Graph

When sampling finishes, the script generates an HTML flame graph file in the ${DORIS_FE_HOME}/log directory. FE performance bottlenecks usually appear as "plateaus" (short and wide). Optimize the code corresponding to those stack frames.

Example flame graph:

Using async-profiler on Older FE Versions

For Doris versions earlier than 2.1.4, download the following two files manually:

1. Download ap-loader-all-3.0-8.jar into the ${DORIS_FE_HOME}/lib directory.
2. Download profile_fe.sh into the ${DORIS_FE_HOME}/bin directory.
3. Run profile_fe.sh to generate the flame graph.

FAQ

Q: The flame graph does not contain stack frames for the target function during sampling.

The corresponding query path was usually not triggered during sampling. While profile_fe.sh is running, send the target SQL repeatedly by hand or with a script, or extend the sampling duration with PROFILE_SECONDS=30.

Q: How do you choose between FE Profiler and Arthas?

• profile_fe.sh: a script-based approach with a fixed sampling duration, suitable for quickly generating a one-off flame graph.
• Arthas: an interactive terminal that supports trace, watch, and other finer-grained runtime observations, suitable for deeper investigation.