Flink重啓策略機制RestartStrategy源碼解讀

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版本號：Flink1.10.0

重啓策略概覽：

public static RestartStrategies.RestartStrategyConfiguration noRestart() {
        return new RestartStrategies.NoRestartStrategyConfiguration();
    }

    public static RestartStrategies.RestartStrategyConfiguration fallBackRestart() {
        return new RestartStrategies.FallbackRestartStrategyConfiguration();
    }

    public static RestartStrategies.RestartStrategyConfiguration fixedDelayRestart(int restartAttempts, long delayBetweenAttempts) {
        return fixedDelayRestart(restartAttempts, Time.of(delayBetweenAttempts, TimeUnit.MILLISECONDS));
    }

    public static RestartStrategies.RestartStrategyConfiguration fixedDelayRestart(int restartAttempts, Time delayInterval) {
        return new RestartStrategies.FixedDelayRestartStrategyConfiguration(restartAttempts, delayInterval);
    }

    public static RestartStrategies.FailureRateRestartStrategyConfiguration failureRateRestart(int failureRate, Time failureInterval, Time delayInterval) {
        return new RestartStrategies.FailureRateRestartStrategyConfiguration(failureRate, failureInterval, delayInterval);
    }

Flink支持多種重啓策略，可以在程序中發生故障時選擇不同的重啓模式進行重啓。常用的重啓策略可以從源碼中看書：

• noRestart
• fallBackRestart
• fixedDelayRestart
• failureRateRestart

parseConfiguration方法

parseConfiguration方法輸入兩個參數：String類型的restartstrategyKind和ReadableConfig類型的configuration，從源碼中可以看出根據var2=restartstrategyKind.toLowerCase()的hashCode值進行匹配給變量var3進行賦值，這樣可以有效的防止hash衝突的問題。

• 當restartstrategyKind爲"none",“off”,“disable"時var3等於"0”,“1”,“2”，此時重啓策略爲noRestart。
• 當restartstrategyKind爲"fixed-delay",“fixeddelay"時，var3等於"3”,“4”。

case 3:
case 4:
     int attempts = (Integer)configuration.get(RestartStrategyOptions.RESTART_STRATEGY_FIXED_DELAY_ATTEMPTS);
     Duration delay = (Duration)configuration.get(RestartStrategyOptions.RESTART_STRATEGY_FIXED_DELAY_DELAY);
     return fixedDelayRestart(attempts, delay.toMillis());

int類型的attempts表示flink作業失敗前的重啓次數。Duration類型的delay表示兩次重啓之間的延遲時間
這裏都調用的是RestartStrategyOptions這個類。

• 當restartstrategyKind爲"failure-rate",“failurerate"時，var3等於"5”,“6”。

case 5:
case 6:
     int maxFailures = (Integer)configuration.get(RestartStrategyOptions.RESTART_STRATEGY_FAILURE_RATE_MAX_FAILURES_PER_INTERVAL);
     Duration failureRateInterval = (Duration)configuration.get(RestartStrategyOptions.RESTART_STRATEGY_FAILURE_RATE_FAILURE_RATE_INTERVAL);
     Duration failureRateDelay = (Duration)configuration.get(RestartStrategyOptions.RESTART_STRATEGY_FAILURE_RATE_DELAY);
     return failureRateRestart(maxFailures, Time.milliseconds(failureRateInterval.toMillis()), Time.milliseconds(failureRateDelay.toMillis()));

int類型的maxFailures表示flink作業最大失敗次數，failureRateInterval表示flink故障率的時間間隔，failureRateDelay表示兩個重啓之間的延遲時間。

代碼測試

// set up the execution environment
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    // operate in Event-time
    env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
    // create a checkpoint every 5 seconds
    env.enableCheckpointing(5000)
    // try to restart 60 times with 10 seconds delay (10 Minutes)
    env.setRestartStrategy(RestartStrategies.fixedDelayRestart(60, Time.of(10, TimeUnit.SECONDS)))

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