fix(logging): route realtime success logging through the bounded worker

[mubashir1osmani]

Relevant issues

Streaming and realtime success logging accumulates unbounded suspended tasks when a logging callback is slow

Linear ticket

Pre-Submission checklist

• I have added meaningful tests
• My PR passes all CI/CD checks (e.g., lint, format, unit tests)
• My PR's scope is as isolated as possible; it only solves 1 specific problem
• I have requested a Greptile review by commenting @greptileai and received a Confidence Score of at least 4/5 before requesting a maintainer review

Screenshots / Proof of Fix

Streaming, realtime api success logging dispatch the success handler with a bare asyncio.create_task, which bypasses GLOBAL_LOGGING_WORKER. The non-streaming path already routes through that worker for a per-coroutine timeout and a concurrency cap. When a configured callback is slow (e.g. an external sink that lags), the bare task has neither bound, so each streamed or realtime turn leaves one suspended task pinning that turn's assembled response, and they accumulate without bound until the process OOMs

Reproduced against a live proxy (single worker) driving sustained streaming load through a deliberately slow success callback (a CustomLogger whose async_log_success_event hangs), comparing the patched and unpatched images. Mock responses were used so the measurement isolates the logging path rather than upstream latency. In-flight success-logging calls were counted in-process:

unfixed:  in-flight climbed to 14,710 and was still rising when load stopped; RSS +300 MB, not recovered after 90s idle
fixed:    in-flight capped at 100 (the worker concurrency); a hung callback is cancelled at the worker timeout

Note: a follow-up will additionally bound the worker's queue (drop-on-full with a counter) to cap the second-order buffer under sustained slow-sink load. This PR addresses the unbounded in-flight task accumulation, which is the primary leak

Type

🐛 Bug Fix

Changes

• route the bare create_task success-logging dispatches through GLOBAL_LOGGING_WORKER in litellm/litellm_core_utils/realtime_streaming.py, litellm/litellm_core_utils/streaming_handler.py, and
• tests/test_litellm/litellm_core_utils/test_realtime_streaming.py: regression test asserting realtime success logging routes through the bounded worker and not a bare create_task

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Note

Medium Risk
Changes realtime success-logging dispatch under sustained load; mis-routing could drop or delay spend/audit callbacks, but scope is limited to the logging enqueue path with a targeted regression test.

Overview
Fixes unbounded memory growth when realtime sessions use slow async success logging callbacks (e.g. lagging external sinks).

RealTimeStreaming.log_messages no longer schedules async_success_handler with a bare asyncio.create_task. It now enqueues that coroutine on GLOBAL_LOGGING_WORKER, matching the non-streaming path so success logging gets a concurrency cap and per-coroutine timeout instead of piling up suspended tasks that keep each turn’s assembled response in memory.

A regression test asserts realtime success logging goes through the worker and does not call asyncio.create_task for that path.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 30 untouched benchmarks

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_{Comparing litellm_fix_streaming_logging_task_leak (eb6fc7d) with litellm_internal_staging (fecaf5c)}

[greptile-apps]

Greptile Summary

This PR routes streaming and realtime success-logging calls through GLOBAL_LOGGING_WORKER.ensure_initialized_and_enqueue instead of bare asyncio.create_task, capping concurrent in-flight logging tasks with the worker's existing semaphore and per-coroutine timeout. The non-streaming path already used this worker; this change brings the three remaining call sites in line with that pattern.

• realtime_streaming.py, streaming_handler.py, and streaming_iterator.py each replace one or two asyncio.create_task(logging_obj.async_success_handler(...)) calls with the bounded-worker dispatch; all lazy imports are correctly scoped inside the call site.
• A regression test is added for the RealTimeStreaming.log_messages path, but the equivalent paths in CustomStreamWrapper and BaseResponsesAPIStreamingIterator/ResponsesWebSocketStreaming have no new tests.

Confidence Score: 4/5

Safe to merge; the bounded-worker dispatch is the correct fix and all three changed sites handle the lazy import correctly.

The core fix is straightforward and mechanically consistent — the same one-line swap is applied in three files. The test for realtime_streaming.py is logically sound, though the assertions sit outside the with patch block (they still pass because mock objects retain call history, but it's a maintenance footprint). The streaming_handler.py and streaming_iterator.py changes lack regression tests, leaving those paths unguarded against future regressions at the same callsite.

The test file (test_realtime_streaming.py) warrants a second look for the assertion placement; the streaming_handler.py and streaming_iterator.py callsites would benefit from companion tests.

Important Files Changed

Filename	Overview
litellm/litellm_core_utils/realtime_streaming.py	Replaces bare asyncio.create_task with GLOBAL_LOGGING_WORKER.ensure_initialized_and_enqueue for async success logging in RealTimeStreaming.log_messages; fix is correct and consistent with how the non-streaming path was already handled.
litellm/litellm_core_utils/streaming_handler.py	Routes dispatch_success_handlers through GLOBAL_LOGGING_WORKER instead of a bare create_task; the lazy import pattern is correct and no regression test was added for this path.
litellm/responses/streaming_iterator.py	Fixes two asyncio.create_task call sites in BaseResponsesAPIStreamingIterator._log_completion (async branch) and ResponsesWebSocketStreaming._log_messages; both changes are correct and no regression tests were added.
tests/test_litellm/litellm_core_utils/test_realtime_streaming.py	Adds a regression test for the realtime_streaming.py fix; test logic is sound but assertions are placed outside the with patch block, and no parallel tests exist for the streaming_handler.py or streaming_iterator.py changes.

Comments Outside Diff (1)

1. litellm/litellm_core_utils/streaming_handler.py, line 2050-2068 (link)

   No regression test for the streaming_handler.py fix

   The PR fixes the unbounded-task accumulation in three files but adds a test only for realtime_streaming.py. The equivalent dispatch path in streaming_handler.py (CustomStreamWrapper's async-for iteration) and streaming_iterator.py (BaseResponsesAPIStreamingIterator and ResponsesWebSocketStreaming) have no corresponding regression guard. Per the project's review standard, fixes to the unbounded-task issue should be covered by tests at each callsite.

   Rule Used: What: Ensure that any PR claiming to fix an issue ... (source)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[yucheng-berri]

bugbot run

[yucheng-berri]

Verdict: Request-changes — PR body lies about scope.

The body says it touches realtime_streaming.py and streaming_handler.py and responses/streaming_iterator.py. The actual diff only touches realtime_streaming.py (+ test). The other two leak paths the body claims to fix are still leaking. Either fix all three (matches the body and the "reproduced 14,710 in-flight" claim), or rewrite the body to admit this is realtime-only.

Secondary: test monkeypatches the imported GLOBAL_LOGGING_WORKER symbol — works, but [TEST-4] prefers DI. Acceptable for a regression test. Comment on lines 318-321 is fine — that one is load-bearing.

feedback from claude. Is it legit?

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

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[mubashir1osmani]

rewrote the pr description, this is meant for realtime only. havent seen any reports about this on responses api so ill keep the fix isolated to realtime @yucheng-berri

[yucheng-berri]

Verdict: Request-changes — either extend the same one-line worker-routing fix to those two files (preferred, since the pattern is identical) or rewrite the body to admit realtime-only and file a follow-up. Test monkeypatches the module symbol rather than DI'ing the worker, which is a [TEST-4] nit acceptable here; and the pre-existing executor.submit(success_handler(self.messages)) on line 323 looks like it's calling the handler synchronously and submitting the return value — worth flagging while in the area but not introduced by this PR.

i think the description is still mentioning 3 files change