hyperledger/fabric · error

buffer is empty

Error message

buffer is empty

What it means

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.

Source

Thrown at orderer/common/follower/block_puller.go:151

// link to said verifier.
func (creator *BlockPullerCreator) UpdateVerifierFromConfigBlock(configBlock *common.Block) error {
	configEnv, err := deliverclient.ConfigFromBlock(configBlock)
	if err != nil {
		return errors.WithMessage(err, "failed to extract config envelope from block")
	}
	verifier, err := creator.blockSigVerifierFactory.VerifierFromConfig(configEnv, creator.channelID)
	if err != nil {
		return errors.WithMessage(err, "failed to construct a block signature verifier from config envelope")
	}
	creator.blockSigVerifier = verifier
	return nil
}

// VerifyBlockSequence verifies a sequence of blocks, using the internal block signature verifier. It also bootstraps
// the block sig verifier form the genesis block if it does not exist, and skips verifying the genesis block.
func (creator *BlockPullerCreator) VerifyBlockSequence(blocks []*common.Block, _ string) error {
	if len(blocks) == 0 {
		return errors.New("buffer is empty")
	}
	if blocks[0] == nil {
		return errors.New("first block is nil")
	}
	if blocks[0].Header == nil {
		return errors.New("first block header is nil")
	}
	if blocks[0].Header.Number == 0 {
		if creator.JoinBlock != nil && creator.JoinBlock.Header.Number == 0 {
			// If we have joined with a genesis block,
			// replace the genesis block we got from the network
			// with our own.
			blocks[0] = creator.JoinBlock
		}
		configEnv, err := deliverclient.ConfigFromBlock(blocks[0])
		if err != nil {
			return errors.WithMessage(err, "failed to extract config envelope from genesis block")
		}

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Fix the caller to not invoke verification on an empty buffer; skip or wait for at least one block
2. Check why the puller returned zero blocks: verify orderer endpoint reachability and TLS settings
3. Verify the requested start/end sequence numbers cover existing blocks in the source ledger
4. Log the puller's request parameters and returned height to confirm the range is correct

Example fix

// before
if err := creator.VerifyBlockSequence(pulledBlocks, channelID); err != nil { ... }
// after
if len(pulledBlocks) == 0 {
    return errors.New("no blocks pulled, skipping verification")
}
if err := creator.VerifyBlockSequence(pulledBlocks, channelID); err != nil { ... }

if len(blocks) == 0 {
    return errors.New("cannot verify empty block sequence; check puller output and range")
}
// proceed to VerifyBlockSequence(blocks, channelID)

func hasBlocks(blocks []*common.Block) bool { return len(blocks) > 0 && blocks[0] != nil }

if err := creator.VerifyBlockSequence(blocks, channelID); err != nil {
    if err.Error() == "buffer is empty" {
        logger.Warnf("no blocks pulled for range, skipping verification")
        return nil
    }
    return err
}

When it happens

Trigger: 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).

Common situations: 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.

Related errors

• first block is nil
• first block header is nil
• could not get application config for the channel
• no config found in envelope
• no source files found in '%s'

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/f63e4a154b6a5548. Report an issue: GitHub.