WatermarkOutputMultiplexer (Flink : Core 1.18.1-cp1 API)

java.lang.Object
- org.apache.flink.api.common.eventtime.WatermarkOutputMultiplexer

```
@Internal
public class WatermarkOutputMultiplexer
extends Object
```
A WatermarkOutputMultiplexer combines the watermark (and idleness) updates of multiple partitions/shards/splits into one combined watermark update and forwards it to an underlying WatermarkOutput.
A multiplexed output can either be immediate or deferred. Watermark updates on an immediate output will potentially directly affect the combined watermark state, which will be forwarded to the underlying output immediately. Watermark updates on a deferred output will only update an internal state but not directly update the combined watermark state. Only when onPeriodicEmit() is called will the deferred updates be combined and forwarded to the underlying output.
For registering a new multiplexed output, you must first call #registerNewOutput(String) and then call getImmediateOutput(String) or getDeferredOutput(String) with the output ID you get from that. You can get both an immediate and deferred output for a given output ID, you can also call the getters multiple times.
WARNING:This class is not thread safe.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static interface WatermarkOutputMultiplexer.WatermarkUpdateListener
A callback for propagating changes to split based watermarks.

Constructor Summary

Constructors
Constructor	Description
`WatermarkOutputMultiplexer(WatermarkOutput underlyingOutput)`	Creates a new `WatermarkOutputMultiplexer` that emits combined updates to the given `WatermarkOutput`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`WatermarkOutput`	`getDeferredOutput(String outputId)`	Returns a deferred `WatermarkOutput` for the given output ID.
`WatermarkOutput`	`getImmediateOutput(String outputId)`	Returns an immediate `WatermarkOutput` for the given output ID.
`void`	`onPeriodicEmit()`	Tells the `WatermarkOutputMultiplexer` to combine all outstanding deferred watermark updates and possibly emit a new update to the underlying `WatermarkOutput`.
`void`	`registerNewOutput(String id, WatermarkOutputMultiplexer.WatermarkUpdateListener onWatermarkUpdate)`	Registers a new multiplexed output, which creates internal states for that output and returns an output ID that can be used to get a deferred or immediate `WatermarkOutput` for that output.
`boolean`	`unregisterOutput(String id)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - WatermarkOutputMultiplexer
```
public WatermarkOutputMultiplexer(WatermarkOutput underlyingOutput)
```
    Creates a new WatermarkOutputMultiplexer that emits combined updates to the given WatermarkOutput.
- Method Detail
  - registerNewOutput
```
public void registerNewOutput(String id,
                              WatermarkOutputMultiplexer.WatermarkUpdateListener onWatermarkUpdate)
```
    Registers a new multiplexed output, which creates internal states for that output and returns an output ID that can be used to get a deferred or immediate WatermarkOutput for that output.
  - unregisterOutput
```
public boolean unregisterOutput(String id)
```
  - getImmediateOutput
```
public WatermarkOutput getImmediateOutput(String outputId)
```
    Returns an immediate WatermarkOutput for the given output ID.
    >See WatermarkOutputMultiplexer for a description of immediate and deferred outputs.
  - getDeferredOutput
```
public WatermarkOutput getDeferredOutput(String outputId)
```
    Returns a deferred WatermarkOutput for the given output ID.
    >See WatermarkOutputMultiplexer for a description of immediate and deferred outputs.
  - onPeriodicEmit
```
public void onPeriodicEmit()
```
    Tells the WatermarkOutputMultiplexer to combine all outstanding deferred watermark updates and possibly emit a new update to the underlying WatermarkOutput.