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Memory Leak Detection

Overview​

ProxySQL includes jemalloc, a memory allocator compiled with profiling capabilities. Since version 1.4.0, memory profiling is enabled by default, but deactivated, allowing the activation at runtime.

Activating the Memory Profiler​

To enable memory profiling at runtime, connect to ProxySQL's Admin interface and execute:

PROXYSQL MEMPROFILE START

This initiates the generation of profile dumps named proxysql.<pid>.<seq>.i<iseq>.heap in:

  • The current working directory (if ProxySQL runs in foreground with -f or --foreground flag)
  • The datadir (default: /var/lib/proxysql) when running as a background process or via init script

To stop profiling, ProxySQL must be restarted.

Reporting Memory Leaks​

Follow these steps when reporting suspected leaks:

  1. Start ProxySQL with profiling enabled
  2. Collect sufficient memory dumps to demonstrate a representative amount of memory consumption
  3. Create a tarball containing the generated dumps
  4. Submit an issue on the ProxySQL GitHub repository using the issue template

Legacy Configuration (Pre-v1.4.0)​

Using Init Script​

Add this environment variable before process startup in /etc/init.d/proxysql:

export MALLOC_CONF="xmalloc:true,lg_tcache_max:16,purge:decay,prof:true,prof_leak:true,lg_prof_sample:18,lg_prof_interval:30"

Without Init Script​

Set the environment variable when launching ProxySQL:

MALLOC_CONF="xmalloc:true,lg_tcache_max:16,purge:decay,prof:true,prof_leak:true,lg_prof_sample:18,lg_prof_interval:30" \
  proxysql -f -c /etc/proxysql.cnf

Retained Memory vs. Leaks​

High virtual memory with low resident memory typically indicates jemalloc's normal retention behavior, not a leak. This appears in stats_memory_metrics when jemalloc_retained exceeds jemalloc_resident.

To disable retention, start ProxySQL with:

MALLOC_CONF="retain:false"

This setting cannot be changed at runtime.