hyperledger/fabric · error

got unexpected sequence from %s - (%d) instead of (%d)

Error message

got unexpected sequence from %s - (%d) instead of (%d)

What it means

pullBlocks expects blocks from a remote orderer to arrive in strict contiguous order starting at nextExpectedSequence. If a block arrives whose Header.Number differs from the expected sequence, the pull is aborted with this error because the stream is out of sync.

Source

Thrown at orderer/common/cluster/deliver.go:239

	var totalSize int
	p.blockBuff = nil
	nextExpectedSequence := seq
	for totalSize < p.MaxTotalBufferBytes && nextExpectedSequence <= p.latestSeq {
		resp, err := stream.Recv()
		if err != nil {
			p.Logger.Errorf("Failed receiving next block from %s: %v", p.endpoint, err)
			return err
		}

		block, err := extractBlockFromResponse(resp)
		if err != nil {
			p.Logger.Errorf("Received a bad block from %s: %v", p.endpoint, err)
			return err
		}
		seq := block.Header.Number
		if seq != nextExpectedSequence {
			p.Logger.Errorf("Expected to receive sequence %d but got %d instead", nextExpectedSequence, seq)
			return errors.Errorf("got unexpected sequence from %s - (%d) instead of (%d)", p.endpoint, seq, nextExpectedSequence)
		}
		size := blockSize(block)
		totalSize += size
		p.blockBuff = append(p.blockBuff, block)
		nextExpectedSequence++
		p.Logger.Infof("[channel: %s] Got block [%d] of size %d KB from %s", p.Channel, seq, size/1024, p.endpoint)
	}
	return nil
}

func (p *BlockPuller) obtainStream(reConnected bool, env *common.Envelope, seq uint64) (*ImpatientStream, error) {
	var stream *ImpatientStream
	var err error
	if reConnected {
		p.Logger.Infof("Sending request for block [%d] to %s", seq, p.endpoint)
		stream, err = p.requestBlocks(p.endpoint, NewImpatientStream(p.conn, p.FetchTimeout), env)
		if err != nil {
			return nil, err

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Retry the pull against another orderer endpoint (standard behavior of the block puller)
2. Verify the remote node is not forked/lagging and is in-sync with the cluster
3. Check for channel reconfiguration/chain migration that may have altered block numbering, then re-pull from a verified height

block, err := puller.pullBlock(seq)
if err != nil {
    if strings.Contains(err.Error(), "got unexpected sequence") {
        // fall back to another endpoint and restart the pull
        block, err = pullerWithNextEndpoint.pullBlock(seq)
    }
}

When it happens

Trigger: During BlockPuller.pullBlocks (invoked via tryFetchBlock), the deliver stream returned block N+2 after N, or restarted at a different sequence than requested.

Common situations: Remote orderer underwent a fallback/consensus hiccup and served a different chain; the start sequence raced with block truncation on the remote node; reconnect landed on a lagging/forked node.

Related errors

• minimum requested sequence is %d but %s is at sequence %d
• block number should have been %d but was %d
• cannot create a block deliverer because height=0
• expected block number=%d, received block number=%d
• unknown orderer type: %s

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/3f11d0931cf2672b. Report an issue: GitHub.