com.google.appengine.tools.mapreduce.impl

Class GoogleCloudStorageSortOutput

java.lang.Object

com.google.appengine.tools.mapreduce.Output<KeyValue<ByteBuffer,List<ByteBuffer>>,FilesByShard>

com.google.appengine.tools.mapreduce.impl.GoogleCloudStorageSortOutput

All Implemented Interfaces:

Serializable

public class GoogleCloudStorageSortOutput
extends Output<KeyValue<ByteBuffer,List<ByteBuffer>>,FilesByShard>

Defines the way data is written out by the sorter. This consists of a single GCS file containing LevelDb format to separate records which are KeyValue pairs. What the key and value are is not known to the sorter, so these are byte arrays that are simply passed through from the mapper. A new file is created at the beginning of each slice in case the data does not all fit in memory.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GoogleCloudStorageSortOutput(String bucket, String mrJobId, Sharder sharder)

Method Summary

Methods

Modifier and Type	Method and Description
List<? extends OutputWriter<KeyValue<ByteBuffer,List<ByteBuffer>>>>	createWriters(int shards) Returns a list of writers, one for each shard, for this output.
FilesByShard	finish(Collection<? extends OutputWriter<KeyValue<ByteBuffer,List<ByteBuffer>>>> writers) 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

GoogleCloudStorageSortOutput

public GoogleCloudStorageSortOutput(String bucket,
                            String mrJobId,
                            Sharder sharder)

Method Detail

createWriters

public List<? extends OutputWriter<KeyValue<ByteBuffer,List<ByteBuffer>>>> 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<ByteBuffer,List<ByteBuffer>>,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<ByteBuffer,List<ByteBuffer>>>> writers)

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<ByteBuffer,List<ByteBuffer>>,FilesByShard>