{"record":{"id":"f14e2bf6f6c865d2","repo":"hyperledger/fabric","slug":"error-decoding-the-previous-hash","errorCode":null,"errorMessage":"error decoding the previous hash","messagePattern":"error decoding the previous hash","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"common/ledger/blkstorage/block_serialization.go","lineNumber":125,"sourceCode":"\t\treturn buf\n\t}\n\tfor _, b := range blockMetadata.Metadata {\n\t\tbuf = protowire.AppendBytes(buf, b)\n\t}\n\treturn buf\n}\n\nfunc extractHeader(buf *buffer) (*common.BlockHeader, error) {\n\theader := &common.BlockHeader{}\n\tvar err error\n\tif header.Number, err = buf.DecodeVarint(); err != nil {\n\t\treturn nil, errors.Wrap(err, \"error decoding the block number\")\n\t}\n\tif header.DataHash, err = buf.DecodeRawBytes(false); err != nil {\n\t\treturn nil, errors.Wrap(err, \"error decoding the data hash\")\n\t}\n\tif header.PreviousHash, err = buf.DecodeRawBytes(false); err != nil {\n\t\treturn nil, errors.Wrap(err, \"error decoding the previous hash\")\n\t}\n\tif len(header.PreviousHash) == 0 {\n\t\theader.PreviousHash = nil\n\t}\n\treturn header, nil\n}\n\nfunc extractData(buf *buffer) (*common.BlockData, []*txindexInfo, error) {\n\tdata := &common.BlockData{}\n\tvar txOffsets []*txindexInfo\n\tvar numItems uint64\n\tvar err error\n\n\tif numItems, err = buf.DecodeVarint(); err != nil {\n\t\treturn nil, nil, errors.Wrap(err, \"error decoding the length of block data\")\n\t}\n\tfor i := uint64(0); i < numItems; i++ {\n\t\tvar txEnvBytes []byte","sourceCodeStart":107,"sourceCodeEnd":143,"githubUrl":"https://github.com/hyperledger/fabric/blob/2736b63f8fd5932511d56fe68b7039d15977f7f6/common/ledger/blkstorage/block_serialization.go#L107-L143","documentation":"extractHeader decodes the PreviousHash field as raw bytes after DataHash. If the buffer cannot supply a valid length-prefixed byte slice there, this error is wrapped and returned. It signals truncation or corruption at the previous-hash position in the serialized block.","triggerScenarios":"deserializeBlock/extractSerializedBlockInfo on bytes cut off inside or right after the data-hash field, so the previous-hash varint length/bytes cannot be read.","commonSituations":"Partial writes to block files during crashes; ledger files copied while the peer was running; corrupted storage after hardware failure.","solutions":["Replace the corrupted block file with a copy from a healthy peer or snapshot backup.","Reset the channel ledger (delete peer ledger data for the channel and re-join) to rebuild from the ordering service.","Always stop the peer before copying or archiving block storage directories.","Verify storage subsystem health and enable redundant storage for ledger volumes."],"exampleFix":"null","handlingStrategy":"try-catch","validationCode":"if len(blockBytes) == 0 {\n    return errors.New(\"empty buffer passed to block deserialization\")\n}","typeGuard":"func isTruncationError(err error) bool {\n    return err != nil && strings.Contains(err.Error(), \"error decoding the previous hash\")\n}","tryCatchPattern":"hdr, err := extractHeader(buf)\nif err != nil {\n    if isTruncationError(err) {\n        logger.Errorf(\"block file truncated mid-header: %v\", err)\n    }\n    return err\n}","preventionTips":["Shut down peers gracefully before host shutdown or container restarts.","Copy block storage only with the peer stopped.","Run periodic integrity checks (e.g. fsck) on ledger volumes.","Store ledgers on storage with power-loss protection."],"tags":["hyperledger-fabric","ledger","serialization","corruption"],"backgroundTag":"ledger-block-corruption","analyzedSha":"2736b63f8fd5932511d56fe68b7039d15977f7f6","analyzedAt":"2026-09-04T08:52:36.465Z","contentChangedAt":"2026-09-04T08:52:36.465Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}