{"record":{"id":"9ab155060373fa2d","repo":"hyperledger/fabric","slug":"could-not-seek-block-file-s-to-startoffset-d","errorCode":null,"errorMessage":"Could not seek block file [%s] to startOffset [%d]. New position = [%d]","messagePattern":"Could not seek block file \\[(.+?)\\] to startOffset \\[(.+?)\\]\\. New position = \\[(.+?)\\]","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"critical","filePath":"common/ledger/blkstorage/block_stream.go","lineNumber":67,"sourceCode":"}\n\n// /////////////////////////////////\n// blockfileStream functions\n// //////////////////////////////////\nfunc newBlockfileStream(rootDir string, fileNum int, startOffset int64) (*blockfileStream, error) {\n\tfilePath := deriveBlockfilePath(rootDir, fileNum)\n\tlogger.Debugf(\"newBlockfileStream(): filePath=[%s], startOffset=[%d]\", filePath, startOffset)\n\tvar file *os.File\n\tvar err error\n\tif file, err = os.OpenFile(filePath, os.O_RDONLY, 0o600); err != nil {\n\t\treturn nil, errors.Wrapf(err, \"error opening block file %s\", filePath)\n\t}\n\tvar newPosition int64\n\tif newPosition, err = file.Seek(startOffset, 0); err != nil {\n\t\treturn nil, errors.Wrapf(err, \"error seeking block file [%s] to startOffset [%d]\", filePath, startOffset)\n\t}\n\tif newPosition != startOffset {\n\t\tpanic(fmt.Sprintf(\"Could not seek block file [%s] to startOffset [%d]. New position = [%d]\",\n\t\t\tfilePath, startOffset, newPosition))\n\t}\n\ts := &blockfileStream{fileNum, file, bufio.NewReader(file), startOffset}\n\treturn s, nil\n}\n\nfunc (s *blockfileStream) nextBlockBytes() ([]byte, error) {\n\tblockBytes, _, err := s.nextBlockBytesAndPlacementInfo()\n\treturn blockBytes, err\n}\n\n// nextBlockBytesAndPlacementInfo returns bytes for the next block\n// along with the offset information in the block file.\n// An error `ErrUnexpectedEndOfBlockfile` is returned if a partial written data is detected\n// which is possible towards the tail of the file if a crash had taken place during appending of a block\nfunc (s *blockfileStream) nextBlockBytesAndPlacementInfo() ([]byte, *blockPlacementInfo, error) {\n\tvar lenBytes []byte\n\tvar err error","sourceCodeStart":49,"sourceCodeEnd":85,"githubUrl":"https://github.com/hyperledger/fabric/blob/2736b63f8fd5932511d56fe68b7039d15977f7f6/common/ledger/blkstorage/block_stream.go#L49-L85","documentation":"A panic (not a returned error) raised when file.Seek reports success but the resulting position does not equal the requested startOffset. Since bufio/os seek on a regular file should always land exactly at the requested offset, this signals an inconsistency the code treats as a programming/environment invariant violation. It crashes the calling goroutine, which in Fabric means crashing the process.","triggerScenarios":"newBlockfileStream where file.Seek(startOffset, 0) returns newPosition != startOffset — practically only when seeking something that is not a regular seekable file (e.g. a special file, or a pipe substituted for the ledger file).","commonSituations":"Ledger 'file' path pointing at a device/FIFO via misconfiguration or bind-mount; exotic FUSE/overlay filesystems reporting wrong positions; tampering or intercepting file I/O (e.g. some security agents).","solutions":["Ensure the ledger path is on a normal local filesystem (ext4/xfs), not a pipe, device, or unusual FUSE mount","Confirm the file at deriveBlockfilePath(rootDir, fileNum) is a regular file (os.Stat mode check)","Recover the process (it panics) and retry after fixing the storage setup"],"exampleFix":"// defensive pre-check before constructing the stream\ninfo, err := os.Stat(deriveBlockfilePath(rootDir, fileNum))\nif err != nil || !info.Mode().IsRegular() {\n    return fmt.Errorf(\"blockfile %s is not a regular file\", path)\n}","handlingStrategy":"validation","validationCode":"info, err := os.Stat(deriveBlockfilePath(rootDir, fileNum))\nif err != nil || !info.Mode().IsRegular() {\n    return fmt.Errorf(\"blockfile %d is not a regular seekable file\", fileNum)\n}","typeGuard":"func isRegularFile(path string) bool {\n    info, err := os.Stat(path)\n    return err == nil && info.Mode().IsRegular()\n}","tryCatchPattern":null,"preventionTips":["Never point the ledger path at devices, FIFOs, or FUSE mounts","Use plain local filesystems (ext4/xfs) for ledger data","Audit container bind-mounts so ledger files remain regular files"],"tags":["fabric","ledger","panic","seek"],"backgroundTag":"seek-position-mismatch","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"}