iamLogIf(ctx, fmt.Errorf("Failure in periodic refresh for IAM (took %.2fs): %v", time.Since(refreshStart).Seconds(), err), logger.WarningKind)
			} else {
				took := time.Since(refreshStart).Seconds()
				if took > maxDurationSecondsForLog {
					// Log if we took a lot of time to load.
					logger.Info("IAM refresh took %.2fs", took)
				}
			}

			// Purge expired STS credentials.