flink missing state value on k8s -在作业管理器/任务管理器崩溃时恢复作业

Question

当flink作业集群(deployment/ pod )在kubernetes上运行时，我们删除了jobmanager和taskmanager(kubectl delete Pod XXX)。我们发现，在pod运行正常后，从PVC挂载rocksDB和检查点文件路径的pod中缺少该状态。在pod运行后，是否有恢复状态的建议？我仔细检查了代码。我发现检查点未启用。是不是作业无法恢复的根本原因？

环境设置如下

RocksDBStateBackend backend = new RocksDBStateBackend(checkPointDataUri + "/checkpoint",true);
        backend.setDbStoragePath(checkPointDataUri + "/RocksDB");
        backend.setNumberOfTransferingThreads(1);

        // add state backend
        env.setStateBackend((StateBackend)backend);

我们可以像下面这样启用检查点吗？

    env.enableCheckpointing(1000);
        env.getCheckpointConfig().setCheckpointingMode(CheckpointingMode.EXACTLY_ONCE);
        env.getCheckpointConfig().setMinPauseBetweenCheckpoints(500);
        env.getCheckpointConfig().setCheckpointTimeout(60000);
        env.getCheckpointConfig().setMaxConcurrentCheckpoints(1);
        env.getCheckpointConfig().enableExternalizedCheckpoints(CheckpointConfig.ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);

下面是重启日志。

2020-06-09 06:48:11,921 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,921 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,962 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,941 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,962 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,941 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,963 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,921 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,963 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,963 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,963 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,942 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,965 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,961 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,965 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,942 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}
2020-06-09 06:48:11,981 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Configuring application-defined state backend with job/cluster config
2020-06-09 06:48:11,944 INFO  org.apache.flink.streaming.runtime.tasks.StreamTask           - Using application-defined state backend: RocksDBStateBackend{checkpointStreamBackend=File State Backend (checkpoints: 'file:/opt/flink/data/ss-kpi-ewfj8/checkpoint', savepoints: 'null', asynchronous: UNDEFINED, fileStateThreshold: -1), localRocksDbDirectories=[/opt/flink/data/ss-kpi-ewfj8/RocksDB], enableIncrementalCheckpointing=TRUE, numberOfTransferingThreads=1}

Answer 1

将RocksDB和检查点存储在同一个文件系统中是没有意义的。RocksDB应该使用最快的本地文件系统-- kubernetes临时存储就可以了。并且检查点必须以持久的方式存储在某种分布式文件系统中。