Method monitor

db.go:2673–2739

monitor runs in a separate goroutine and monitors the database & WAL. Implements exponential backoff on repeated sync errors to prevent disk churn when persistent errors (like disk full) occur. See issue #927.

()

// Implements exponential backoff on repeated sync errors to prevent disk churn
// when persistent errors (like disk full) occur. See issue #927.
func (db *DB) monitor() {
	ticker := time.NewTicker(db.MonitorInterval)
	defer ticker.Stop()

	// Backoff state for error handling.
	var backoff time.Duration
	var lastLogTime time.Time
	var consecutiveErrs int

	for {
		// Wait for ticker or context close.
		select {
		case <-db.ctx.Done():
			return
		case <-ticker.C:
		}

		// If in backoff mode, wait additional time before retrying.
		if backoff > 0 {
			select {
			case <-db.ctx.Done():
				return
			case <-time.After(backoff):
			}
		}

		// Sync the database to the shadow WAL.
		if err := db.Sync(db.ctx); err != nil && !errors.Is(err, context.Canceled) {
			consecutiveErrs++

			// Exponential backoff: MonitorInterval -> 2x -> 4x -> ... -> max
			if backoff == 0 {
				backoff = db.MonitorInterval
			} else {
				backoff *= 2
				if backoff > DefaultSyncBackoffMax {
					backoff = DefaultSyncBackoffMax
				}
			}

			// Log with rate limiting to avoid log spam during persistent errors.
			if time.Since(lastLogTime) >= SyncErrorLogInterval {
				db.Logger.Error("sync error",
					"error", err,
					"consecutive_errors", consecutiveErrs,
					"backoff", backoff)
				lastLogTime = time.Now()
			}

			// Try to clean up stale temp files after persistent disk errors.
			if isDiskFullError(err) && consecutiveErrs >= 3 {
				db.Logger.Warn("attempting temp file cleanup due to persistent disk errors")
				if cleanupErr := removeTmpFiles(db.metaPath); cleanupErr != nil {
					db.Logger.Error("temp file cleanup failed", "error", cleanupErr)
				}
			}
			continue
		}