pyflink.datastream.state_backend.HashMapStateBackend

class HashMapStateBackend(j_hashmap_state_backend=None)

This state backend holds the working state in the memory (JVM heap) of the TaskManagers and checkpoints based on the configured CheckpointStorage.

State Size Considerations

Working state is kept on the TaskManager heap. If a TaskManager executes multiple tasks concurrently (if the TaskManager has multiple slots, or if slot-sharing is used) then the aggregate state of all tasks needs to fit into that TaskManager’s memory.

Configuration

As for all state backends, this backend can either be configured within the application (by creating the backend with the respective constructor parameters and setting it on the execution environment) or by specifying it in the Flink configuration.

If the state backend was specified in the application, it may pick up additional configuration parameters from the Flink configuration. For example, if the backend if configured in the application without a default savepoint directory, it will pick up a default savepoint directory specified in the Flink configuration of the running job/cluster. That behavior is implemented via the configure() method.