{"record":{"id":"f63e4a154b6a5548","repo":"hyperledger/fabric","slug":"buffer-is-empty-f63e4a","errorCode":null,"errorMessage":"buffer is empty","messagePattern":"buffer is empty","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"orderer/common/follower/block_puller.go","lineNumber":151,"sourceCode":"// link to said verifier.\nfunc (creator *BlockPullerCreator) UpdateVerifierFromConfigBlock(configBlock *common.Block) error {\n\tconfigEnv, err := deliverclient.ConfigFromBlock(configBlock)\n\tif err != nil {\n\t\treturn errors.WithMessage(err, \"failed to extract config envelope from block\")\n\t}\n\tverifier, err := creator.blockSigVerifierFactory.VerifierFromConfig(configEnv, creator.channelID)\n\tif err != nil {\n\t\treturn errors.WithMessage(err, \"failed to construct a block signature verifier from config envelope\")\n\t}\n\tcreator.blockSigVerifier = verifier\n\treturn nil\n}\n\n// VerifyBlockSequence verifies a sequence of blocks, using the internal block signature verifier. It also bootstraps\n// the block sig verifier form the genesis block if it does not exist, and skips verifying the genesis block.\nfunc (creator *BlockPullerCreator) VerifyBlockSequence(blocks []*common.Block, _ string) error {\n\tif len(blocks) == 0 {\n\t\treturn errors.New(\"buffer is empty\")\n\t}\n\tif blocks[0] == nil {\n\t\treturn errors.New(\"first block is nil\")\n\t}\n\tif blocks[0].Header == nil {\n\t\treturn errors.New(\"first block header is nil\")\n\t}\n\tif blocks[0].Header.Number == 0 {\n\t\tif creator.JoinBlock != nil && creator.JoinBlock.Header.Number == 0 {\n\t\t\t// If we have joined with a genesis block,\n\t\t\t// replace the genesis block we got from the network\n\t\t\t// with our own.\n\t\t\tblocks[0] = creator.JoinBlock\n\t\t}\n\t\tconfigEnv, err := deliverclient.ConfigFromBlock(blocks[0])\n\t\tif err != nil {\n\t\t\treturn errors.WithMessage(err, \"failed to extract config envelope from genesis block\")\n\t\t}","sourceCodeStart":133,"sourceCodeEnd":169,"githubUrl":"https://github.com/hyperledger/fabric/blob/2736b63f8fd5932511d56fe68b7039d15977f7f6/orderer/common/follower/block_puller.go#L133-L169","documentation":"VerifyBlockSequence validates a pulled sequence of blocks; if the slice is empty there is nothing to verify, so it rejects the call immediately. Callers usually hit this when the block puller returned zero blocks for the requested range.","triggerScenarios":"Calling VerifyBlockSequence with an empty []*common.Block, typically after a block pull that fetched nothing (wrong start/end sequence, unreachable orderer returning no blocks, or caller bug passing uninitialized buffer).","commonSituations":"Follower pulling blocks during channel join when the ordering endpoint is unreachable and the puller silently returns an empty batch; off-by-one in requested block range; tests constructing an empty block buffer.","solutions":["Fix the caller to not invoke verification on an empty buffer; skip or wait for at least one block","Check why the puller returned zero blocks: verify orderer endpoint reachability and TLS settings","Verify the requested start/end sequence numbers cover existing blocks in the source ledger","Log the puller's request parameters and returned height to confirm the range is correct"],"exampleFix":"// before\nif err := creator.VerifyBlockSequence(pulledBlocks, channelID); err != nil { ... }\n// after\nif len(pulledBlocks) == 0 {\n    return errors.New(\"no blocks pulled, skipping verification\")\n}\nif err := creator.VerifyBlockSequence(pulledBlocks, channelID); err != nil { ... }","handlingStrategy":"type-guard","validationCode":"if len(blocks) == 0 {\n    return errors.New(\"cannot verify empty block sequence; check puller output and range\")\n}\n// proceed to VerifyBlockSequence(blocks, channelID)","typeGuard":"func hasBlocks(blocks []*common.Block) bool { return len(blocks) > 0 && blocks[0] != nil }","tryCatchPattern":"if err := creator.VerifyBlockSequence(blocks, channelID); err != nil {\n    if err.Error() == \"buffer is empty\" {\n        logger.Warnf(\"no blocks pulled for range, skipping verification\")\n        return nil\n    }\n    return err\n}","preventionTips":["Check puller return values: do not call verify on empty results","Validate requested start/end sequence against source ledger height before pulling","Treat zero-block pulls as a connectivity signal and check orderer endpoints"],"tags":["blocks","verification","empty-input"],"backgroundTag":"empty-block-buffer","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"}