How to check what code is currently running on a server?

ClickHouse provides introspection tools like `system.stack_trace` for inspecting what code is currently running on each server thread, helping with debugging and performance monitoring.

Check what code is currently running on a server

ClickHouse has a built-in debugger and introspection capabilities.

For example, you can get the stack traces of every server's thread at runtime by querying the system.stack_trace table:

The query result will show the locations in the ClickHouse source code where the threads are running or waiting. (You will need to set allow_introspection_functions to 1 to enable the introspection functions.) The response looks like:

Note

If you installed ClickHouse from a .deb/.rpm/.tgz you can also install the package with the debug info to see the line numbers from the source code:

If you've installed ClickHouse as a single-binary, it already contains the debug info.

Tip

For more high-level information, check out some of these other system tables:

• system.processes
• system.query_log
• system.metric_log
• system.asynchronous_metric_log
• system.trace_log
• system.processor_profile_log

And there is handy info in the other system tables also.

Mar 24, 2023 · 3 min read