{"record":{"id":"f5ef08d71847992e","repo":"hyperledger/fabric","slug":"error-decoding-the-data-hash","errorCode":null,"errorMessage":"error decoding the data hash","messagePattern":"error decoding the data hash","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"common/ledger/blkstorage/block_serialization.go","lineNumber":122,"sourceCode":"\t}\n\tbuf = protowire.AppendVarint(buf, numItems)\n\tif blockMetadata == nil {\n\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\")","sourceCodeStart":104,"sourceCodeEnd":140,"githubUrl":"https://github.com/hyperledger/fabric/blob/2736b63f8fd5932511d56fe68b7039d15977f7f6/common/ledger/blkstorage/block_serialization.go#L104-L140","documentation":"After decoding the block number, extractHeader decodes the header's DataHash as raw bytes. A failure here means the buffer ran out or the length prefix was invalid while reading the data hash field of the serialized block. The serialized block is malformed or truncated.","triggerScenarios":"Deserializing a block whose bytes end (or are corrupt) between the block-number field and the data-hash field — via deserializeBlock or extractSerializedBlockInfo on damaged blkstorage data.","commonSituations":"Truncated block files after an unclean shutdown or disk-full event; ledger directories restored from incomplete backups; tampered/partial block bytes fed by custom tooling.","solutions":["Restore the affected block store files from a valid backup or resync the channel from peers/orderers.","Wipe and rebuild the peer's ledger for that channel (remove ledger data, re-join the channel).","Check filesystem/disk integrity (fsck, SMART) on the ledger volume.","If from tooling, ensure the block was serialized with the same Fabric block serialization format before decoding."],"exampleFix":"null","handlingStrategy":"try-catch","validationCode":"if len(blockBytes) < minSerializedHeaderLen {\n    return fmt.Errorf(\"block bytes too short (%d) to contain a header\", len(blockBytes))\n}","typeGuard":"func isHeaderDecodeFailure(err error) bool {\n    return err != nil && (strings.Contains(err.Error(), \"error decoding the data hash\") ||\n        strings.Contains(err.Error(), \"error decoding the block number\"))\n}","tryCatchPattern":"info, err := extractSerializedBlockInfo(buf)\nif err != nil {\n    if isHeaderDecodeFailure(err) {\n        // mark block file suspect, trigger ledger rebuild/resync\n    }\n    return err\n}","preventionTips":["Use filesystem snapshots/atomic copies when archiving ledgers.","Keep the peer and its storage on reliable, redundant disks.","Validate restored backups by deserializing the first and last blocks before serving traffic.","Avoid interrupting file transfers of ledger data mid-write."],"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"}