{"record":{"id":"a9cfb120e595b051","repo":"vitessio/vitess","slug":"failed-to-get-a-worker-from-pool-s","errorCode":null,"errorMessage":"failed to get a worker from pool: %s","messagePattern":"failed to get a worker from pool: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"warning","filePath":"go/vt/vttablet/tabletmanager/vreplication/vcopier.go","lineNumber":794,"sourceCode":"\t}\n\tvcq.isOpen = false\n\tvcq.workerPool.Close()\n}\n\n// enqueue a new copy task. This will obtain a worker from the pool, execute\n// the task with that worker, and afterwards return the worker to the pool. If\n// vcopierCopyWorkQueue is configured to operate concurrently, the task will be\n// executed in a separate goroutine. Otherwise the task will be executed in the\n// calling goroutine.\nfunc (vcq *vcopierCopyWorkQueue) enqueue(ctx context.Context, currT *vcopierCopyTask) error {\n\tif !vcq.isOpen {\n\t\treturn errors.New(\"work queue is not open\")\n\t}\n\n\t// Get a handle on an unused worker.\n\tpoolH, err := vcq.workerPool.Get(ctx)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"failed to get a worker from pool: %s\", err.Error())\n\t}\n\n\tcurrW, ok := poolH.(*vcopierCopyWorker)\n\tif !ok {\n\t\treturn errors.New(\"failed to cast pool resource to *vcopierCopyWorker\")\n\t}\n\n\texecute := func(task *vcopierCopyTask) {\n\t\tcurrW.execute(ctx, task)\n\t\tvcq.workerPool.Put(poolH)\n\t}\n\n\t// If the work queue is configured to work concurrently, execute the task\n\t// in a separate goroutine. Otherwise execute the task in the calling\n\t// goroutine.\n\tif vcq.concurrent {\n\t\tgo execute(currT)\n\t} else {","sourceCodeStart":776,"sourceCodeEnd":812,"githubUrl":"https://github.com/vitessio/vitess/blob/01a25a7d176f94613b8d59d799f438380a8760e4/go/vt/vttablet/tabletmanager/vreplication/vcopier.go#L776-L812","documentation":"vcopier.enqueue hands each copy task to a worker from a nugget-style resource pool. If pool.Get(ctx) fails — typically because the context was cancelled while waiting for a free worker or because the pool is closed — the enqueue fails with this wrapped error.","triggerScenarios":"enqueue called while all copy workers are busy and ctx is cancelled (workflow stop/delete, engine close, tablet shutdown) before a worker becomes available, or the pool has been closed.","commonSituations":"Workflow cancelled mid-copy; vttablet shutting down during heavy parallel copy; copy queue depth exceeding worker pool capacity combined with a short ctx timeout.","solutions":["Check if the workflow/tablet was stopping — this error is expected during cancellation; retry the copy phase","Increase copy worker parallelism or reduce maxDepth so tasks don't wait long for workers","Ensure ctx used for enqueue has a generous timeout","Inspect vttablet logs for pool close/shutdown events preceding the error"],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"err := vcq.enqueue(ctx, task)\nif err != nil {\n  if errors.Is(err, context.Canceled) || strings.Contains(err.Error(), \"failed to get a worker from pool\") {\n    // expected during shutdown/cancel; resubmit after recovery\n  }\n  return err\n}","preventionTips":["Size the worker pool >= expected concurrent copy tasks","Don't cancel the workflow context while copies are in flight","Tune queue maxDepth relative to parallelism"],"tags":["vreplication","vcopier","worker-pool","cancellation"],"backgroundTag":"context-cancelled-waiting-for-worker","analyzedSha":"01a25a7d176f94613b8d59d799f438380a8760e4","analyzedAt":"2026-09-01T17:28:30.605Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}