Failed to restore checkpointed states using Flink Processor API

Question

The main program is consuming kafka events, then filter -> map -> keyBy -> CEP -> sink. I wrote another separate simple program to read checkpoint directory like the following:

object StateReader extends App {

  val path = "file://...."

  val env = ExecutionEnvironment.getExecutionEnvironment

  val chk = Savepoint.load(env.getJavaEnv, path, new FsStateBackend(path))

  val ds = chk.readKeyedState("cep", new CepOperatorReadFunction, TypeInformation.of(classOf[KEY]), TypeInformation.of(classOf[VALUE]))
  println(ds.count())

}

class CepOperatorReadFunction extends KeyedStateReaderFunction[KEY, VALUE] {
  override def open(parameters: Configuration): Unit = {

  }
  override def readKey(k: KEY, context: KeyedStateReaderFunction.Context, collector: Collector[VALUE]): Unit = {

  }//end readKey
}//end class CepOperatorReadFunction

However I got the following exception:

Caused by: java.lang.IllegalStateException: Unexpected state handle type, expected: class org.apache.flink.runtime.state.KeyGroupsStateHandle, but found: class org.apache.flink.runtime.state.IncrementalRemoteKeyedStateHandle
    at org.apache.flink.runtime.state.heap.HeapRestoreOperation.restore(HeapRestoreOperation.java:120)
    at org.apache.flink.runtime.state.heap.HeapKeyedStateBackendBuilder.build(HeapKeyedStateBackendBuilder.java:114)
    ... 13 more

Here are some configuraitons in flink-conf.yaml

state.backend: rocksdb
state.checkpoints.dir: hdfs:///.../checkpoints
state.savepoints.dir: hdfs:///.../savepoints
state.backend.incremental: true
state.backend.rocksdb.memory.write-buffer-ratio: 0.6
state.backend.rocksdb.localdir: /var/lib/.../rocksdb
execution.checkpointing.interval: 900000
execution.checkpointing.timeout: 600000
execution.checkpointing.unaligned: true
execution.checkpointing.mode: EXACTLY_ONCE
execution.checkpointing.max-concurrent-checkpoints: 1
execution.checkpointing.min-pause: 0

Any ideas why the exception happened and how to fix the problem?

Thanks

Answer 1

There's no out-of-the-box support to make reading the CEP operator's state easy. So to implement your KeyedStateReaderFunction , you'll have to dig into the CEP implementation, find the ValueState s and MapState s that are used, and implement a reader that uses those same state descriptors.