{"record":{"id":"e128f7f7bd418ae7","repo":"juicedata/juicefs","slug":"inode-d-slice-d-w","errorCode":null,"errorMessage":"inode %d slice %d : %w","messagePattern":"inode (.+?) slice (.+?) : %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/vfs/fill.go","lineNumber":466,"sourceCode":"\t\t\tcontinue\n\t\t}\n\t\tvar bytes uint64\n\t\tfor _, p := range parts {\n\t\t\tbytes += uint64(p.Len)\n\t\t}\n\t\tatomic.AddUint64(&iter.stat.SliceCount, 1)\n\t\tatomic.AddUint64(&iter.stat.TotalBytes, bytes)\n\n\t\tselect {\n\t\tcase concurrent <- token{}:\n\t\t\twg.Add(1)\n\t\t\tgo func() {\n\t\t\t\tdefer func() {\n\t\t\t\t\t<-concurrent\n\t\t\t\t\twg.Done()\n\t\t\t\t}()\n\t\t\t\tif err := handler(s, parts); err != nil {\n\t\t\t\t\titer.err = fmt.Errorf(\"inode %d slice %d : %w\", iter.ino, s.Id, err)\n\t\t\t\t}\n\t\t\t}()\n\t\tdefault:\n\t\t\tif err := handler(s, parts); err != nil {\n\t\t\t\titer.err = fmt.Errorf(\"inode %d slice %d : %w\", iter.ino, s.Id, err)\n\t\t\t}\n\t\t}\n\t}\n\twg.Wait()\n\treturn iter.err\n}\n\nfunc newSliceIterator(ctx meta.Context, mClient meta.Meta, ino Ino, size uint64, stat *CacheResponse, ranges []ByteRange) *sliceIterator {\n\treturn &sliceIterator{\n\t\tctx:     ctx,\n\t\tmClient: mClient,\n\t\tino:     ino,\n\t\tstat:    stat,","sourceCodeStart":448,"sourceCodeEnd":484,"githubUrl":"https://github.com/juicedata/juicefs/blob/c9a67b23e8e08ec23ec331aa6f1675e2319e921c/pkg/vfs/fill.go#L448-L484","documentation":"When sliceIterator.Iterate runs a slice handler on a background goroutine (the concurrent channel path), any error the handler returns is captured into iter.err wrapped as \"inode %d slice %d : %w\". The error identifies which inode and which slice id failed, preserving the underlying cause via %w. It is reported after wg.Wait() as the return value of Iterate.","triggerScenarios":"A sliceHandler invoked asynchronously by Iterate returns a non-nil error, e.g. the cache-fill handler fails to load or register slice parts for a given slice of the inode.","commonSituations":"Prefetch/cache-warm operations where the object store is unreachable or a block download fails while filling chunks for an inode; a handler closure capturing a resource (channel, store client) that has since been closed.","solutions":["Inspect the wrapped cause (%w) to find the real failure; fix that first.","Verify object storage connectivity and credentials used by the chunk loader.","Add per-slice error logging in your handler to pinpoint the failing part.","Retry the iterate/fill operation; it only failed for one slice."],"exampleFix":"// before\nif err := handler(s, parts); err != nil {\n    iter.err = fmt.Errorf(\"inode %d slice %d : %w\", iter.ino, s.Id, err)\n}\n// after\nif err := handler(s, parts); err != nil {\n    iter.err = fmt.Errorf(\"inode %d slice %d : %w\", iter.ino, s.Id, err)\n    return // in handler: return err so caller can errors.As the root cause\n}","handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"if err := iter.Iterate(handler, concurrent); err != nil {\n    var cause error\n    if errors.As(err, &cause) && cause != err {\n        log.Printf(\"fill failed: %v (cause: %v)\", err, cause)\n    }\n    // retry only the failed slice if handler is idempotent\n}","preventionTips":["Keep slice handlers idempotent so retries are safe.","Pre-warm object-storage connectivity before large fill operations.","Log slice ids to correlate failures with specific chunks."],"tags":["go","vfs","error-wrapping","concurrency"],"backgroundTag":"api-error-response","analyzedSha":"c9a67b23e8e08ec23ec331aa6f1675e2319e921c","analyzedAt":"2026-09-06T17:55:48.476Z","contentChangedAt":"2026-09-06T17:55:48.476Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}