java为什么flink 1.10.1在flink crashrestart与FsStateBackend一起启动后不加载存储状态

3 月，3 周 Questions & Answers 134

我正在使用Flink 1.10.1和FsStateBackend作为检查点的状态后端。我有一些有状态的操作，在应用程序运行期间（作为.jar应用程序而不是集群运行），它们按照预期工作，但是如果应用程序由于某种原因停止（或崩溃），应该存储在文件系统中的状态（带有检查点）不会被加载，函数也不会有任何以前的引用，然后我需要从数据库中加载信息，并将其保存为状态，以便再次处理这些以前的状态。必须有一种方法可以使用检查点和fsstatebend实现这一点，而不必读取数据库中的所有信息，只需从已存储的检查点重新加载此状态即可。这可能吗

下面是一些代码：我的检查点配置

final StreamExecutionEnvironment env = StreamExecutionEnvironment.createLocalEnvironment(8, GetConfiguration.getConfig());
final StateBackend stateBackend = new FsStateBackend(new Path("/some/path/checkpoints").toUri(), true);
            env.getCheckpointConfig().enableExternalizedCheckpoints(CheckpointConfig.ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);
            env.getCheckpointConfig().setMinPauseBetweenCheckpoints(5000);
            env.getCheckpointConfig().setMaxConcurrentCheckpoints(1);

env.enableCheckpointing(30000, CheckpointingMode.EXACTLY_ONCE);
 env.getCheckpointConfig().setCheckpointTimeout(60000);
            env.getCheckpointConfig().setTolerableCheckpointFailureNumber(10);
            env.getCheckpointConfig().setPreferCheckpointForRecovery(true);
            env.setRestartStrategy(RestartStrategies.noRestart());
            env.setStateBackend(stateBackend);

这就是我想要避免的例子：

public class EventCountMap extends RichMapFunction<Event, EventCounter> {
    private static final MapStateDescriptor<String, Timestamp> descriptor = new MapStateDescriptor<>("previous_counter", String.class, Timestamp.class);
    private static final EventCounter eventCounter = new EventCounter();
    private MapState<String, Timestamp> previous_state;
    private static final StateTtlConfig ttlConfig = StateTtlConfig
            .newBuilder(org.apache.flink.api.common.time.Time.days(1))
            .cleanupFullSnapshot()
            .build();

    @Override
    public void open(Configuration parameters) {
        descriptor.enableTimeToLive(ttlConfig);
        previous_state = getRuntimeContext().getMapState(descriptor);
    }

/*I want to avoid to call this function that load all events from db and pass them to the state to be used. This happens only once but there must be a efficient way to do this in flink.*/
    private void mapRefueled() throws Exception {
        Preconditions.checkNotNull(previous_state);
        for (Map.Entry<String, Timestamp> map : StreamingJob.update_beh_count_ts.entrySet())
            previous_state.put(map.getKey(), map.getValue());
        StreamingJob.update_beh_count_ts.clear();
    }

    @Override
    public EventCounter map(Event event) throws Exception {
        /*Refuel map state in case of failures*/
        if (!StreamingJob.update_beh_count_ts.isEmpty()) mapRefueled();
        eventCounter.date = new Date(event.timestamp.getTime());
        final String key_first = eventCounter.date.toString().concat("_ts_first");
        final String key_last = eventCounter.date.toString().concat("_ts_last");
        if (previous_state.contains(key_first) && previous_state.contains(key_last)) {
            final Timestamp first = (previous_state.get(key_first).after(event.timestamp)) ? event.timestamp : previous_state.get(key_first);
            final Timestamp last = (previous_state.get(key_last).before(event.timestamp)) ? event.timestamp : previous_state.get(key_last);
            previous_state.put(key_first, first);
            previous_state.put(key_last, last);
        } else {
            previous_state.put(key_first, event.timestamp);
            previous_state.put(key_last, event.timestamp);
        }
        eventCounter.first_event = previous_state.get(key_first);
        eventCounter.last_event = previous_state.get(key_last);
        return eventCounter;
    }
}

希望我能为你解释一下我需要做什么。亲切的问候！提前谢谢

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