org.apache.tez.runtime.api
Interface Output

All Known Subinterfaces:

LogicalOutput

public interface Output

Represents an Output through which a TezProcessor writes information on an edge.

Output implementations must have a 0 argument public constructor for Tez to construct the Output. Tez will take care of initializing and closing the Input after a Processor completes.

During initialization, Outputs must specify an initial memory requirement via TezOutputContext.requestInitialMemory

Method Summary

List<Event>	close() Closes the Output
Writer	getWriter() Gets an instance of the Writer in an Output
void	handleEvents(List<Event> outputEvents) Handles user and system generated Events, which typically carry information such as a downstream vertex being ready to consume input.
List<Event>	initialize(TezOutputContext outputContext) Initializes the Output
void	start() Start any processing that the Output may need to perform.

Method Detail

initialize

List<Event> initialize(TezOutputContext outputContext)
                       throws Exception

Initializes the Output

Parameters:

outputContext - the TezOutputContext

Returns:

list of events that were generated during initialization

Throws:

Exception - if an error occurs

start

void start()
           throws Exception

Start any processing that the Output may need to perform. It is the responsibility of the Processor to start Outputs. This typically acts as a signal to Outputs to start any Processing that they may required. This method may be invoked by the framework under certain circumstances, and as such requires the implementation to be non-blocking. Outputs must be written to handle multiple start invocations - typically honoring only the first one.

Throws:

Exception

getWriter

Writer getWriter()
                 throws Exception

Gets an instance of the Writer in an Output

Returns:

Gets an instance of the Writer in an Output

Throws:

Exception - if an error occurs

handleEvents

void handleEvents(List<Event> outputEvents)

Handles user and system generated Events, which typically carry information such as a downstream vertex being ready to consume input.

Parameters:

outputEvents - the list of Events

close

List<Event> close()
                  throws Exception

Closes the Output

Returns:

list of events that were generated during close

Throws:

Exception - if an error occurs