Use weak reference in langchain instrumentation span map #3820
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Oct 10, 2025
| # TODO: Use weak references or a TTL cache to avoid memory leaks in long-running processes. See #3735 | ||
| self.spans: Dict[UUID, _SpanState] = {} | ||
| # Using a TTL cache to avoid memory leaks in long-running processes where end_span might not be called. | ||
| self.spans: TTLCache[UUID, _SpanState] = TTLCache(maxsize=1024, ttl=3600) |
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Isn't weakref enough? https://docs.python.org/3/library/weakref.html
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I went ahead and experimented with using a WeakValueDictionary, but it would be a much larger refactor as we
store don't hold a strong ref to _SpanState outside of span_manager, if I am correct. Let me know your thoughts please, thank you.
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Description
Use weak reference in langchain instrumentation span map to avoid memory leaks in long running applications via span storage. Added "cachetools >= 5.2.0" to dependencies.
Fixes #3735
Type of change
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How Has This Been Tested?
Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration
test_ttl_cache_expires_spanstotest_span_managerDoes This PR Require a Core Repo Change?
Checklist:
See contributing.md for styleguide, changelog guidelines, and more.