org.apache.samza.operators.windows

Interface Window<M extends MessageEnvelope,K,WV,WM extends WindowPane<K,WV>>

Type Parameters:

M - the type of the input MessageEnvelope

K - the type of the key in the MessageEnvelope in this MessageStream.

WV - the type of the value in the WindowPane.

WM - the type of the output.

All Known Implementing Classes:

WindowInternal

@InterfaceStability.Unstable
public interface Window<M extends MessageEnvelope,K,WV,WM extends WindowPane<K,WV>>

Groups incoming MessageEnvelopes 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 MessageEnvelopes in the window and is called a WindowPane. A pane can include all MessageEnvelopes collected for the window so far or only the new MessageEnvelopes 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 of late data arrivals.

A Window is defined as "keyed" when the incoming MessageStream is first partitioned based on the provided key, and windowing is applied on the partitioned 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 the Windows APIs to create various windows and the Triggers APIs to create triggers.

Method Summary

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

Method Detail

setEarlyTrigger

Window<M,K,WV,WM> 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,WM> 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,WM> 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 (key) 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 (key) since the last emitted window pane.

Parameters:

mode - the accumulation mode

Returns:

the Window function with the specified AccumulationMode.