vitessio/vitess · error

--dry_run is only supported for SwitchTraffic, ReverseTraffi

Error message

--dry_run is only supported for SwitchTraffic, ReverseTraffic and Complete, not for %s

What it means

The --dry_run flag is only meaningful for the SwitchTraffic, ReverseTraffic, and Complete actions of a vreplication workflow. Passing --dry_run with any other action is rejected so users are not misled into thinking a preview occurred. The error names the actual action that was given.

Source

Thrown at go/vt/vtctl/vtctl.go:2386

				}
				if progress.SourceTableSize > 0 {
					tableSizePct = 100.0 * progress.TargetTableSize / progress.SourceTableSize
				}
				fmt.Fprintf(&sSb2360, "%s: rows copied %d/%d (%d%%), size copied %d/%d (%d%%)\n",
					table, progress.TargetRowCount, progress.SourceRowCount, rowCountPct,
					progress.TargetTableSize, progress.SourceTableSize, tableSizePct)
			}
			s += sSb2360.String()
			wr.Logger().Printf("\n%s\n", s)
		}
		return printDetails()
	}

	if *dryRun {
		switch action {
		case vReplicationWorkflowActionSwitchTraffic, vReplicationWorkflowActionReverseTraffic, vReplicationWorkflowActionComplete:
		default:
			return fmt.Errorf("--dry_run is only supported for SwitchTraffic, ReverseTraffic and Complete, not for %s", originalAction)
		}
	}

	wr.WorkflowParams = vrwp

	switch vrwp.WorkflowType {
	case wrangler.MoveTablesWorkflow:
		// If this is not a partial MoveTables, SourceShards is nil and all shards will be polled.
		shardsWithStreams = vrwp.SourceShards
	case wrangler.ReshardWorkflow:
		shardsWithStreams = vrwp.TargetShards
	default:
	}

	wr.WorkflowParams = vrwp
	var dryRunResults *[]string
	startState := wf.CachedState()
	switch action {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Remove --dry_run for this action
2. Restrict dry-run usage to SwitchTraffic, ReverseTraffic, or Complete actions
3. Preview the change another way, e.g. inspect workflow state with `show`

Example fix

// before
vtctldclient Reshard cancel commerce.reshard --dry_run
// after
vtctldclient Reshard complete commerce.reshard --dry_run  # or drop --dry_run for cancel

dryRunAllowed := map[string]bool{"switchtraffic": true, "reversetraffic": true, "complete": true}
if dryRun && !dryRunAllowed[action] {
  // drop --dry_run or change action
}

When it happens

Trigger: `vtctldclient ... create --dry_run`, `cancel --dry_run`, `show --dry_run`, etc.; scripted dry-run attempts against StartTraffic/StopTraffic or Cancel actions.

Common situations: Users assuming dry-run is universally supported across workflow actions; converting a SwitchTraffic dry-run script to a Cancel action while keeping the flag.

Related errors

• invalid --limit value (%d), maximum number of rows to compar
• invalid format for external source cluster: %s
• invalid value for on-ddl: %v
• invalid action for Migrate: %s
• unknown workflow type passed: %v

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/2524793836160748. Report an issue: GitHub.