com.google.appengine.tools.mapreduce.impl

Class GoogleCloudStorageMapOutput<K,V>

java.lang.Object

com.google.appengine.tools.mapreduce.Output<KeyValue<K,V>,FilesByShard>

com.google.appengine.tools.mapreduce.impl.GoogleCloudStorageMapOutput<K,V>

Type Parameters:

K - type of intermediate keys

V - type of intermediate values

All Implemented Interfaces:

Serializable

public class GoogleCloudStorageMapOutput<K,V>
extends Output<KeyValue<K,V>,FilesByShard>

An Output that is used for the map stage. This consists of a number of GCS files where the content is split up by the provided Sharder.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GoogleCloudStorageMapOutput(String bucket, String mrJobId, Marshaller<K> keyMarshaller, Marshaller<V> valueMarshaller, Sharder sharder)

Method Summary

Methods

Modifier and Type	Method and Description
List<? extends OutputWriter<KeyValue<K,V>>>	createWriters(int shards) Returns a list of writers, one for each shard, for this output.
FilesByShard	finish(Collection<? extends OutputWriter<KeyValue<K,V>>> outputWriters) Returns a result to be made available through MapReduceResult.getOutputResult().

Methods inherited from class com.google.appengine.tools.mapreduce.Output

getContext, setContext

Methods inherited from class java.lang.Object

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

Constructor Detail

GoogleCloudStorageMapOutput

public GoogleCloudStorageMapOutput(String bucket,
                           String mrJobId,
                           Marshaller<K> keyMarshaller,
                           Marshaller<V> valueMarshaller,
                           Sharder sharder)

Method Detail

createWriters

public List<? extends OutputWriter<KeyValue<K,V>>> createWriters(int shards)

Description copied from class: Output

Returns a list of writers, one for each shard, for this output.

Specified by:

createWriters in class Output<KeyValue<K,V>,FilesByShard>

Parameters:

shards - The number of shards which should be equal to the number of OutputWriters returned.

finish

public FilesByShard finish(Collection<? extends OutputWriter<KeyValue<K,V>>> outputWriters)
                    throws IOException

Description copied from class: Output

Returns a result to be made available through MapReduceResult.getOutputResult().

This method allows the Output to inspect the final state of its OutputWriters to produce a final result object. For example, if the OutputWriters produce blobs in blobstore, finish could collect and return a list of blob IDs.

Should return null if no such result makes sense for this kind of output.

Called after all OutputWriters have been closed (with OutputWriter.close()). It is possible for this method to be called more than once with the same writers collection. It is also possible for the job to fail after this is invoked.

The writers argument will contain the same writers that Output.createWriters(int) returned in the same order. Writers may be serialized and deserialized multiple times. typically, getWriter will have been called in a different JVM.

Specified by:

finish in class Output<KeyValue<K,V>,FilesByShard>

Throws:

IOException