the required parameter 'blockNumber' is empty or set to 0. R

Error message

the required parameter 'blockNumber' is empty or set to 0. Rerun the command with -b flag

What it means

The peer snapshot cancelrequest command requires the block number at which the snapshot was requested, passed via -b/--blockNumber. validateCancelRequest rejects the command when blockNumber is unset or explicitly 0, since 0 is not a valid snapshot request block number to cancel.

Source

Thrown at internal/peer/snapshot/cancelrequest.go:87

	if err != nil {
		return err
	}

	_, err = cl.snapshotClient.Cancel(context.Background(), signedRequest)
	if err != nil {
		return errors.WithMessage(err, "failed to cancel the request")
	}

	fmt.Fprint(cl.writer, "Snapshot request cancelled successfully\n")
	return nil
}

func validateCancelRequest() error {
	if channelID == "" {
		return errors.New("the required parameter 'channelID' is empty. Rerun the command with -c flag")
	}
	if blockNumber == 0 {
		return errors.New("the required parameter 'blockNumber' is empty or set to 0. Rerun the command with -b flag")
	}
	return nil
}

View on GitHub (pinned to 2736b63f8f)

Solutions

Rerun with a nonzero block number: peer snapshot cancelrequest -c <channelID> -b <blockNumber>.
Use 'peer snapshot listpending' to find valid pending block numbers to cancel.
Validate the block number variable is > 0 in scripts before invoking.

Example fix

// before
peer snapshot cancelrequest -c mychannel -b 0
// after
peer snapshot cancelrequest -c mychannel -b 1500

Defensive patterns

Strategy: validation

Validate before calling

if [ -z "$BLOCK" ] || [ "$BLOCK" -le 0 ] 2>/dev/null; then
  echo "blockNumber must be a positive integer"; exit 1
fi
peer snapshot cancelrequest -c "$CHANNEL" -b "$BLOCK"

Prevention

Run 'peer snapshot listpending' first to obtain valid block numbers
Reject zero/empty block numbers in scripts
Remember -b is mandatory for cancelrequest

When it happens

Trigger: Running 'peer snapshot cancelrequest' without -b, or with -b 0; passing a non-numeric value that parses to the zero value.

Common situations: Scripts where the block-number variable defaulted to 0 or failed to expand; mistaking the flag for optional; using a block number from a different channel that was never requested.

Understand the failure class

Background: "--flag is required" and "must specify" CLI errors: how missing-required-flag validation works and how to fix it — this error's family across 20 libraries.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/d7e0d9ef70a15455. Report an issue: GitHub.