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Three race conditions in multi_worker_connection_manager could leave the Redis profile_connections:<id> counter permanently elevated with no active streams, causing all VOD requests to 503 "All profiles at capacity". Bug 1 — decrement_active_streams() return value was ignored All three generator exit paths (normal, GeneratorExit, Exception) called decrement_active_streams() and unconditionally set decremented = True regardless of whether the lock was acquired. On lock contention the decrement was silently skipped, active_streams remained > 0, the subsequent has_active_streams() check returned True, and _decrement_profile_connections() was never called. The counter was then stuck until manual DEL. Fix: add decrement_active_streams_and_check() which performs the decrement and the "are there remaining streams?" check atomically under a single lock, eliminating the race window. All three exit paths and the finally block now use this method and propagate its success/remaining return values. Bug 2 — non-atomic GET-then-DECR in _decrement_profile_connections() The previous implementation read the counter with GET then conditionally called DECR. Two concurrent decrements could both pass the > 0 guard and both fire, driving the counter to -1. A subsequent _check_and_reserve_profile_slot() INCR would then produce 0 which passes the <= max_streams check, allowing an extra stream to bypass the limit on the next request. Fix: replace GET-then-DECR with a direct DECR (matching the INCR-first pattern already used by _check_and_reserve_profile_slot) and clamp the result to 0 if it goes negative. Bug 3 — has_active_streams() read state without holding the lock The separate has_active_streams() call after decrement_active_streams() released its lock left a window where another concurrent stream could increment active_streams back to 1, causing the profile decrement to be skipped. This is resolved as a consequence of Bug 1's fix: the new decrement_active_streams_and_check() method reads active_streams while the lock is still held, eliminating the window entirely. Adds tests covering all three scenarios in apps/proxy/vod_proxy/tests/test_profile_connections.py. Fixes #1121. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> |
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| __init__.py | ||
| test_profile_connections.py | ||