org.apache.beam.sdk.io

Class WriteFiles<T>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PCollection<T>,PDone>

org.apache.beam.sdk.io.WriteFiles<T>

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

@Experimental(value=SOURCE_SINK)
public class WriteFiles<T>
extends PTransform<PCollection<T>,PDone>

A PTransform that writes to a FileBasedSink. A write begins with a sequential global initialization of a sink, followed by a parallel write, and ends with a sequential finalization of the write. The output of a write is PDone.

By default, every bundle in the input PCollection will be processed by a FileBasedSink.WriteOperation, so the number of output will vary based on runner behavior, though at least 1 output will always be produced. The exact parallelism of the write stage can be controlled using withNumShards(int), typically used to control how many files are produced or to globally limit the number of workers connecting to an external service. However, this option can often hurt performance: it adds an additional GroupByKey to the pipeline.

Example usage with runner-determined sharding:

 p.apply(WriteFiles.to(new MySink(...)));

Example usage with a fixed number of shards:

 p.apply(WriteFiles.to(new MySink(...)).withNumShards(3));

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.beam.sdk.transforms.PTransform

name

Method Summary

Modifier and Type	Method and Description
PDone	expand(PCollection<T> input) Override this method to specify how this PTransform should be expanded on the given InputT.
ValueProvider<java.lang.Integer>	getNumShards()
PTransform<PCollection<T>,PCollectionView<java.lang.Integer>>	getSharding() Gets the PTransform that will be used to determine sharding.
FileBasedSink<T>	getSink() Returns the FileBasedSink associated with this PTransform.
boolean	isWindowedWrites() Returns whether or not to perform windowed writes.
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
static <T> WriteFiles<T>	to(FileBasedSink<T> sink) Creates a WriteFiles transform that writes to the given FileBasedSink, letting the runner control how many different shards are produced.
void	validate(PipelineOptions options) Called before running the Pipeline to verify this transform is fully and correctly specified.
WriteFiles<T>	withMaxNumWritersPerBundle(int maxNumWritersPerBundle) Set the maximum number of writers created in a bundle before spilling to shuffle.
WriteFiles<T>	withNumShards(int numShards) Returns a new WriteFiles that will write to the current FileBasedSink using the specified number of shards.
WriteFiles<T>	withNumShards(ValueProvider<java.lang.Integer> numShardsProvider) Returns a new WriteFiles that will write to the current FileBasedSink using the ValueProvider specified number of shards.
WriteFiles<T>	withRunnerDeterminedSharding() Returns a new WriteFiles that will write to the current FileBasedSink with runner-determined sharding.
WriteFiles<T>	withSharding(PTransform<PCollection<T>,PCollectionView<java.lang.Integer>> sharding) Returns a new WriteFiles that will write to the current FileBasedSink using the specified PTransform to compute the number of shards.
WriteFiles<T>	withWindowedWrites() Returns a new WriteFiles that writes preserves windowing on it's input.

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, toString

Methods inherited from class java.lang.Object

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

Method Detail

to

public static <T> WriteFiles<T> to(FileBasedSink<T> sink)

Creates a WriteFiles transform that writes to the given FileBasedSink, letting the runner control how many different shards are produced.

expand

public PDone expand(PCollection<T> input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

Specified by:

expand in class PTransform<PCollection<T>,PDone>

validate

public void validate(PipelineOptions options)

Description copied from class: PTransform

Called before running the Pipeline to verify this transform is fully and correctly specified.

By default, does nothing.

Overrides:

validate in class PTransform<PCollection<T>,PDone>

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Description copied from class: PTransform

Register display data for the given transform or component.

populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace, but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace of the subcomponent.

By default, does not register any display data. Implementors may override this method to provide their own display data.

Specified by:

populateDisplayData in interface HasDisplayData

Overrides:

populateDisplayData in class PTransform<PCollection<T>,PDone>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData

getSink

public FileBasedSink<T> getSink()

Returns the FileBasedSink associated with this PTransform.

isWindowedWrites

public boolean isWindowedWrites()

Returns whether or not to perform windowed writes.

getSharding

@Nullable
public PTransform<PCollection<T>,PCollectionView<java.lang.Integer>> getSharding()

Gets the PTransform that will be used to determine sharding. This can be either a static number of shards (as following a call to withNumShards(int)), dynamic (by withSharding(PTransform)), or runner-determined (by withRunnerDeterminedSharding().

getNumShards

public ValueProvider<java.lang.Integer> getNumShards()

withNumShards

public WriteFiles<T> withNumShards(int numShards)

Returns a new WriteFiles that will write to the current FileBasedSink using the specified number of shards.

This option should be used sparingly as it can hurt performance. See WriteFiles for more information.

A value less than or equal to 0 will be equivalent to the default behavior of runner-determined sharding.

withNumShards

public WriteFiles<T> withNumShards(ValueProvider<java.lang.Integer> numShardsProvider)

Returns a new WriteFiles that will write to the current FileBasedSink using the ValueProvider specified number of shards.

This option should be used sparingly as it can hurt performance. See WriteFiles for more information.

withMaxNumWritersPerBundle

public WriteFiles<T> withMaxNumWritersPerBundle(int maxNumWritersPerBundle)

Set the maximum number of writers created in a bundle before spilling to shuffle.

withSharding

public WriteFiles<T> withSharding(PTransform<PCollection<T>,PCollectionView<java.lang.Integer>> sharding)

Returns a new WriteFiles that will write to the current FileBasedSink using the specified PTransform to compute the number of shards.

This option should be used sparingly as it can hurt performance. See WriteFiles for more information.

withRunnerDeterminedSharding

public WriteFiles<T> withRunnerDeterminedSharding()

Returns a new WriteFiles that will write to the current FileBasedSink with runner-determined sharding.

withWindowedWrites

public WriteFiles<T> withWindowedWrites()

Returns a new WriteFiles that writes preserves windowing on it's input.

If this option is not specified, windowing and triggering are replaced by GlobalWindows and DefaultTrigger.

If there is no data for a window, no output shards will be generated for that window. If a window triggers multiple times, then more than a single output shard might be generated multiple times; it's up to the sink implementation to keep these output shards unique.

This option can only be used if withNumShards(int) is also set to a positive value.