org.apache.tez.runtime.api

Class InputInitializer

java.lang.Object

org.apache.tez.runtime.api.InputInitializer

@InterfaceStability.Unstable
 @InterfaceAudience.Public
public abstract class InputInitializer
extends Object

InputInitializers are typically used to initialize vertices connected to data sources. They run in the App Master and can be used to distribute data across the tasks for the vertex, determine the number of tasks at runtime, update the Input payload etc.

Constructor Summary

Constructors

Constructor and Description
InputInitializer(InputInitializerContext initializerContext) Constructor an instance of the InputInitializer.

Method Summary

Modifier and Type	Method and Description
InputInitializerContext	getContext() Return ahe InputInitializerContext for this specific instance of the Initializer.
abstract void	handleInputInitializerEvent(List<InputInitializerEvent> events) Handle events meant for the specific Initializer.
abstract List<Event>	initialize() Run the initializer.
void	onVertexStateUpdated(VertexStateUpdate stateUpdate) Receive notifications on vertex state changes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

InputInitializer

public InputInitializer(InputInitializerContext initializerContext)

Constructor an instance of the InputInitializer. Classes extending this to create a InputInitializer, must provide the same constructor so that Tez can create an instance of the class at runtime.

Parameters:

initializerContext - initializer context which can be used to access the payload, vertex properties, etc

Method Detail

initialize

public abstract List<Event> initialize()
                                throws Exception

Run the initializer. This is the main method where initialization takes place. If an Initializer is written to accept events, a notification mechanism should be setup, with the heavy lifting of processing the event being done via this method. The moment this method returns a list of events, input initialization is considered to be complete.

Returns:

a list of events which are eventually routed to a VertexManagerPlugin for routing

Throws:

Exception

handleInputInitializerEvent

public abstract void handleInputInitializerEvent(List<InputInitializerEvent> events)
                                          throws Exception

Handle events meant for the specific Initializer. This is a notification mechanism to inform the Initializer about events received. Extensive event processing should not be performed via this method call. Instead this should just be used as a notification method to the main initialization via the initialize method.

Parameters:

events - list of events

Throws:

Exception

getContext

public final InputInitializerContext getContext()

Return ahe InputInitializerContext for this specific instance of the Initializer.

Returns:

the InputInitializerContext for the initializer

onVertexStateUpdated

public void onVertexStateUpdated(VertexStateUpdate stateUpdate)
                          throws Exception

Receive notifications on vertex state changes.

State changes will be received based on the registration via InputInitializerContext.registerForVertexStateUpdates(String, java.util.Set). Notifications will be received for all registered state changes, and not just for the latest state update. They will be in order in which the state change occurred.

Extensive processing should not be performed via this method call. Instead this should just be used as a notification mechanism to the main initialization, which is via the initialize method.
This method may be invoked concurrently with initialize() etc. and multi-threading/concurrency implications must be considered.

Parameters:

stateUpdate - an event indicating the name of the vertex, and it's updated state. Additional information may be available for specific events, Look at the type hierarchy for VertexStateUpdate

Throws:

Exception