@Override
    public String toString() {
        return MoreObjects.toStringHelper(this)
                          .add("isHealthy", isHealthy)
                          .add("ttlMillis", ttlMillis)
                          .toString();
    }
Return the interval for scheduling the next check.
core/src/main/java/com/linecorp/armeria/server/healthcheck/HealthCheckStatus.java