如果要考虑易用性和效率,使用rocksDB来替代普通内存的kv是有必要的 有了rocksdb,可以range查询,可以支持columnfamily,可以各种压缩 但是rocksdb本身是一个库,是跑在RocksDBStateBackend中的 所以taskmanager挂掉后,数据还是没了, 所以RocksDBStateBackend仍然需要类似HDFS这样的分布式存储来存储snapshot   kv state需要由rockdb来管理,这是和内存或file backend最大的不同 Abstr…

All transformations in Flink may look like functions (in the functional processing terminology), but are in fact stateful operators. You can make every transformation (map, filter, etc) stateful by using Flink's state interface or checkpointing insta…

State Backends 本文翻译自文档Streaming Guide / Fault Tolerance / StateBackend ----------------------------------------------------------------------------------------- 使用Data Stream API编写的程序通常以多种形式维护状态: ·  窗口将收集element或在它被触发后聚合element ·  Transformation方法可能会…

January 23, 2018- Apache Flink, Flink Features Stefan Richter and Chris Ward Apache Flink was purpose-built for stateful stream processing. Let’s quickly review: what is state in a stream processing application? I defined state and stateful stream pr…

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checkpoint介绍 checkpoint机制是Flink可靠性的基石,可以保证Flink集群在某个算子因为某些原因(如 异常退出)出现故障时,能够将整个应用流图的状态恢复到故障之前的某一状态,保 证应用流图状态的一致性.Flink的checkpoint机制原理来自“Chandy-Lamport algorithm”算法. 每个需要checkpoint的应用在启动时,Flink的JobManager为其创建一个 CheckpointCoordinator,CheckpointCoordina…

https://mp.weixin.qq.com/s?__biz=MjM5NjQ5MTI5OA==&mid=2651749037&idx=1&sn=4a448647b3dae50779bc9ec0e9c10275&chksm=bd12a3e08a652af6ed8b305b0523716e08a81cf99296425cdaf2bbee1e9d8a6aca06c81cdcc1&scene=21#wechat_redirect 总第291篇 2018年 第83篇 引言…

https://mp.weixin.qq.com/s/nQOxsZUZSiPi7Sx40mgwsA 20181104 3 differences between Savepoints and Checkpoints in Apache Flink data-artisans Flink 昨天 This episode of our Flink Friday Tip explains what Savepoints and Checkpoints are and examines the main…

一.从何说起 State要能发挥作用,就需要持久化到可靠存储中,flink中持久化的动作就是checkpointing,那么从TM中执行的Task的基类StreamTask的checkpoint逻辑说起. 1.streamTask StreamTask protected OperatorChain<OUT, OP> operatorChain; CheckpointStreamFactory createCheckpointStreamFactory(StreamOperator<?&…

1.总览 savepoints是外部存储的自包含的checkpoints,可以用来stop and resume,或者程序升级.savepoints利用checkpointing机制来创建流式作业的状态的完整快照(非增量快照),将checkpoint的数据和元数据都写入到一个外部文件系统. 如何触发.恢复或者释放savepoint了?下面一一道来. 2.分配Operator ID 极度推荐你给每个方法分配一个uid,这样才可以升级应用.ID起到的作用是明确每个operator的状态的使用范围.…