Alexander Frolov d07c1c73d1 lib/writeconcurrencylimiter: prevent deadlock at IncConcurrency ...

Previously (*writeconcurrencylimiter.Reader).Read() could permanently leak concurrency tokens from the -maxConcurrentInserts semaphore.
 
 Consider the following example:
* GetReader() acquires a token, then PutReader() unconditionally releases it.
* Read() calls DecConcurrency() before the underlying I/O and IncConcurrency() after it. If IncConcurrency() returns an error, Read() returns without holding a token.
* Each such failure permanently removes one slot from the concurrencyLimitCh semaphore. Slots leak one by one until the channel is fully drained, at which point DecConcurrency() blocks forever, deadlocking ingestion on vmstorage.

 This commit adds tracking for obtained tokens to the reader. Which prevents possible tokens leakage. 

Fixes https://github.com/VictoriaMetrics/VictoriaMetrics/issues/10784

2026-04-10 19:35:59 +02:00

..

concurrencylimiter.go

lib/writeconcurrencylimiter: prevent deadlock at IncConcurrency

2026-04-10 19:35:59 +02:00