K
- Type of the keysOUT
- Type of the output elements.@PublicEvolving public abstract class KeyedStateReaderFunction<K,OUT> extends AbstractRichFunction
For every key readKey(Object, Context, Collector)
is invoked. This can produce zero
or more elements as output.
NOTE: State descriptors must be eagerly registered in open(Configuration)
. Any
attempt to dynamically register states inside of readKey
will result in a RuntimeException
.
NOTE: A KeyedStateReaderFunction
is always a RichFunction
. Therefore, access to the RuntimeContext
is always available and setup and teardown
methods can be implemented. See RichFunction.open(Configuration)
and RichFunction.close()
.
Modifier and Type | Class and Description |
---|---|
static interface |
KeyedStateReaderFunction.Context
Context that
KeyedStateReaderFunction 's can use for getting additional data about an
input record. |
Constructor and Description |
---|
KeyedStateReaderFunction() |
Modifier and Type | Method and Description |
---|---|
abstract void |
open(Configuration parameters)
Initialization method for the function.
|
abstract void |
readKey(K key,
KeyedStateReaderFunction.Context ctx,
Collector<OUT> out)
Process one key from the restored state backend.
|
close, getIterationRuntimeContext, getRuntimeContext, setRuntimeContext
public abstract void open(Configuration parameters) throws Exception
readKey(Object, Context,
Collector)
and thus suitable for one time setup work.
This is the only method that my register state descriptors within a KeyedStateReaderFunction
.
open
in interface RichFunction
open
in class AbstractRichFunction
parameters
- The configuration containing the parameters attached to the contract.Exception
- Implementations may forward exceptions, which are caught by the runtime.
When the runtime catches an exception, it aborts the task and lets the fail-over logic
decide whether to retry the task execution.Configuration
public abstract void readKey(K key, KeyedStateReaderFunction.Context ctx, Collector<OUT> out) throws Exception
This function can read partitioned state from the restored state backend and output zero
or more elements using the Collector
parameter.
key
- The input value.out
- The collector for returning result values.Exception
- This method may throw exceptions. Throwing an exception will cause the
operation to fail and may trigger recovery.Copyright © 2014–2021 The Apache Software Foundation. All rights reserved.