fix: Avoid mixed Langfuse traces in async envs #2207
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github-actions
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integration:langfuse
type:documentation
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Replacing #2188 |
anakin87
reviewed
Aug 21, 2025
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Asking @mpangrazzi a review since he was originally involved. Let's also adjust the title. |
vblagoje
changed the title
vblagoje
changed the title
Looks good! Tested on both simple pipelines and agent (nested) pipelines.
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I checked complex agents and examples pipelines. All good. Thanks a lot for the confirmation @LastRemote 💪 |
mpangrazzi
approved these changes
Aug 22, 2025
| if self._context and self._context[-1] == span: | ||
| self._context.pop() | ||
| # Restore previous span stack using saved token - ensures proper cleanup | ||
| span_stack_var.reset(token) |
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Can we safely assume this line will never throw an error?
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No mention of it in pydocs anywhere. Seems like it can't happen
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Fixed and released in https://pypi.org/project/langfuse-haystack/2.3.0/ |
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Why:
Purpose: Fixes a race condition where spans from concurrent pipeline runs become intertwined, corrupting tracing data and making debugging unreliable in production web server environments.
LangfuseTraceris not thread-safe, causing mixed traces in async environments #2140What:
self._contextlist withContextVarfor thread-safe span stack managementLangfuseTracer.trace()method to use context-local span storagecurrent_span()method to read from context-local statespan_context_varContextVar for isolated span contexts per execution threadHow can it be used:
Nothing changes in client code except that we don't corrupt traces in concurrent async pipelines. All existing usage patterns continue to work exactly as before, but now with proper thread safety.
How did you test it: