Method printStatus

go/logic/migrator.go:1375–1440

printStatus prints the progress status, and optionally additionally detailed dump of configuration. `rule` indicates the type of output expected. By default the status is written to standard output, but other writers can be used as well.

(rule PrintStatusRule, writers ...io.Writer)

// By default the status is written to standard output, but other writers can
// be used as well.
func (mgtr *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
	if rule == NoPrintStatusRule {
		return
	}
	writers = append(writers, os.Stdout)

	elapsedTime := mgtr.migrationContext.ElapsedTime()
	elapsedSeconds := int64(elapsedTime.Seconds())
	totalRowsCopied := mgtr.migrationContext.GetTotalRowsCopied()
	rowsEstimate := atomic.LoadInt64(&mgtr.migrationContext.RowsEstimate) + atomic.LoadInt64(&mgtr.migrationContext.RowsDeltaEstimate)
	if atomic.LoadInt64(&mgtr.rowCopyCompleteFlag) == 1 {
		// Done copying rows. The totalRowsCopied value is the de-facto number of rows,
		// and there is no further need to keep updating the value.
		rowsEstimate = totalRowsCopied
	}

	// we take the opportunity to update migration context with progressPct
	progressPct := mgtr.getProgressPercent(rowsEstimate)
	mgtr.migrationContext.SetProgressPct(progressPct)

	// Before status, let's see if we should print a nice reminder for what exactly we're doing here.
	if mgtr.shouldPrintMigrationStatusHint(rule, elapsedSeconds) {
		mgtr.printMigrationStatusHint(writers...)
	}

	// Get state + ETA
	state, eta, etaDuration := mgtr.getMigrationStateAndETA(rowsEstimate)
	mgtr.migrationContext.SetETADuration(etaDuration)

	if !mgtr.shouldPrintStatus(rule, elapsedSeconds, etaDuration) {
		return
	}

	currentBinlogCoordinates := mgtr.eventsStreamer.GetCurrentBinlogCoordinates()

	status := fmt.Sprintf("Copy: %d/%d %.1f%%; Applied: %d; Backlog: %d/%d; Time: %+v(total), %+v(copy); streamer: %+v; Lag: %.2fs, HeartbeatLag: %.2fs, State: %s; ETA: %s",
		totalRowsCopied, rowsEstimate, progressPct,
		atomic.LoadInt64(&mgtr.migrationContext.TotalDMLEventsApplied),
		len(mgtr.applyEventsQueue), cap(mgtr.applyEventsQueue),
		base.PrettifyDurationOutput(elapsedTime), base.PrettifyDurationOutput(mgtr.migrationContext.ElapsedRowCopyTime()),
		currentBinlogCoordinates.DisplayString(),
		mgtr.migrationContext.GetCurrentLagDuration().Seconds(),
		mgtr.migrationContext.TimeSinceLastHeartbeatOnChangelog().Seconds(),
		state,
		eta,
	)
	mgtr.applier.WriteChangelog(
		fmt.Sprintf("copy iteration %d at %d", mgtr.migrationContext.GetIteration(), time.Now().Unix()),
		state,
	)
	w := io.MultiWriter(writers...)
	fmt.Fprintln(w, status)

	// This "hack" is required here because the underlying logging library
	// github.com/outbrain/golib/log provides two functions Info and Infof; but the arguments of
	// both these functions are eventually redirected to the same function, which internally calls
	// fmt.Sprintf. So, the argument of every function called on the DefaultLogger object
	// migrationContext.Log will eventually pass through fmt.Sprintf, and thus the '%' character