org.apache.samza.operators.windows

Interface Window<M,K,WV>

Type Parameters:

M - the type of the input message

K - the type of the key in the message

WV - the type of the value in the window

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

WindowInternal

@InterfaceStability.Unstable
public interface Window<M,K,WV>
extends java.io.Serializable

Groups incoming messages in the MessageStream into finite windows for processing.

A window is uniquely identified by its WindowKey. A window can have one or more associated Triggers that determine when results from the Window are emitted.

Each emitted result contains one or more messages in the window and is called a WindowPane. A pane can include all messages collected for the window so far or only the new messages since the last emitted pane. (as determined by the AccumulationMode)

A window can have early triggers that allow emitting WindowPanes speculatively before all data for the window has arrived, or late triggers that allow handling late arrivals of data.

A Window is said to be as "keyed" when the incoming MessageStream is first grouped based on the provided key, and windowing is applied on the grouped stream.

                                     window wk1 (with its triggers)
                                      +--------------------------------+
                                      ------------+--------+-----------+
                                      |           |        |           |
                                      | pane 1    |pane2   |   pane3   |
                                      +-----------+--------+-----------+

 -----------------------------------
     incoming message stream ------+
 -----------------------------------
                                      window wk2
                                      +---------------------+---------+
                                      |   pane 1|   pane 2  |  pane 3 |
                                      |         |           |         |
                                      +---------+-----------+---------+

                                      window wk3
                                      +----------+-----------+---------+
                                      |          |           |         |
                                      | pane 1   |  pane 2   |   pane 3|
                                      |          |           |         |
                                      +----------+-----------+---------+

Use Windows to create various windows and Triggers to create their triggers.

Method Summary

Modifier and Type	Method and Description
Window<M,K,WV>	setAccumulationMode(AccumulationMode mode) Specify how a Window should process its previously emitted WindowPanes.
Window<M,K,WV>	setEarlyTrigger(Trigger<M> trigger) Set the early triggers for this Window.
Window<M,K,WV>	setLateTrigger(Trigger<M> trigger) Set the late triggers for this Window.

Method Detail

setEarlyTrigger

Window<M,K,WV> setEarlyTrigger(Trigger<M> trigger)

Set the early triggers for this Window.

Use the Triggers APIs to create instances of Trigger

Parameters:

trigger - the early trigger

Returns:

the Window function with the early trigger

setLateTrigger

Window<M,K,WV> setLateTrigger(Trigger<M> trigger)

Set the late triggers for this Window.

Use the Triggers APIs to create instances of Trigger

Parameters:

trigger - the late trigger

Returns:

the Window function with the late trigger

setAccumulationMode

Window<M,K,WV> setAccumulationMode(AccumulationMode mode)

Specify how a Window should process its previously emitted WindowPanes.

There are two types of AccumulationModes:

• ACCUMULATING: Specifies that window panes should include all messages collected for the window so far, even if they were included in previously emitted window panes.
• DISCARDING: Specifies that window panes should only include messages collected for this window since the last emitted window pane.

Parameters:

mode - the accumulation mode

Returns:

the Window function with mode set as its AccumulationMode.