org.apache.beam.sdk.io

Class FileBasedSource<T>

java.lang.Object

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

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

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

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

Type Parameters:

T - Type of records represented by the source.

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

Direct Known Subclasses:

BlockBasedSource, CompressedSource, XmlSource

public abstract class FileBasedSource<T>
extends OffsetBasedSource<T>

A common base class for all file-based Sources. Extend this class to implement your own file-based custom source.

A file-based Source is a Source backed by a file pattern defined as a Java glob, a single file, or a offset range for a single file. See OffsetBasedSource and RangeTracker for semantics of offset ranges.

This source stores a String that is a FileSystems specification for a file or file pattern. There should be a FileSystem registered for the file specification provided. Please refer to FileSystems and FileSystem for more information on this.

In addition to the methods left abstract from BoundedSource, subclasses must implement methods to create a sub-source and a reader for a range of a single file - createForSubrangeOfFile(org.apache.beam.sdk.io.fs.MatchResult.Metadata, long, long) and createSingleFileReader(org.apache.beam.sdk.options.PipelineOptions). Please refer to TextIO.TextSource for an example implementation of FileBasedSource.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FileBasedSource.FileBasedReader<T> A reader that implements code common to readers of FileBasedSources.
static class	FileBasedSource.Mode A given FileBasedSource represents a file resource of one of these types.

Nested classes/interfaces inherited from class org.apache.beam.sdk.io.OffsetBasedSource

OffsetBasedSource.OffsetBasedReader<T>

Nested classes/interfaces inherited from class org.apache.beam.sdk.io.BoundedSource

BoundedSource.BoundedReader<T>

Nested classes/interfaces inherited from class org.apache.beam.sdk.io.Source

Source.Reader<T>

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	FileBasedSource(MatchResult.Metadata fileMetadata, long minBundleSize, long startOffset, long endOffset) Create a FileBasedSource based on a single file.
protected	FileBasedSource(ValueProvider<java.lang.String> fileOrPatternSpec, long minBundleSize) Create a FileBaseSource based on a file or a file pattern specification.

Method Summary

Modifier and Type	Method and Description
protected abstract FileBasedSource<T>	createForSubrangeOfFile(MatchResult.Metadata fileMetadata, long start, long end) Creates and returns a new FileBasedSource of the same type as the current FileBasedSource backed by a given file and an offset range.
BoundedSource.BoundedReader<T>	createReader(PipelineOptions options) Returns a new BoundedSource.BoundedReader that reads from this source.
protected abstract FileBasedSource.FileBasedReader<T>	createSingleFileReader(PipelineOptions options) Creates and returns an instance of a FileBasedReader implementation for the current source assuming the source represents a single file.
FileBasedSource<T>	createSourceForSubrange(long start, long end) Returns an OffsetBasedSource for a subrange of the current source.
long	getEstimatedSizeBytes(PipelineOptions options) An estimate of the total size (in bytes) of the data that would be read from this source.
java.lang.String	getFileOrPatternSpec()
ValueProvider<java.lang.String>	getFileOrPatternSpecProvider()
long	getMaxEndOffset(PipelineOptions options) Returns the actual ending offset of the current source.
FileBasedSource.Mode	getMode()
protected MatchResult.Metadata	getSingleFileMetadata() Returns the information about the single file that this source is reading from.
protected boolean	isSplittable() Determines whether a file represented by this source is can be split into bundles.
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
java.util.List<? extends FileBasedSource<T>>	split(long desiredBundleSizeBytes, PipelineOptions options) Splits the source into bundles of approximately desiredBundleSizeBytes.
java.lang.String	toString()
void	validate() Checks that this source is valid, before it can be used in a pipeline.

Methods inherited from class org.apache.beam.sdk.io.OffsetBasedSource

getBytesPerOffset, getEndOffset, getMinBundleSize, getStartOffset

Methods inherited from class org.apache.beam.sdk.io.Source

getDefaultOutputCoder

Methods inherited from class java.lang.Object

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

Constructor Detail

FileBasedSource

protected FileBasedSource(ValueProvider<java.lang.String> fileOrPatternSpec,
                          long minBundleSize)

Create a FileBaseSource based on a file or a file pattern specification.

FileBasedSource

protected FileBasedSource(MatchResult.Metadata fileMetadata,
                          long minBundleSize,
                          long startOffset,
                          long endOffset)

Create a FileBasedSource based on a single file. This constructor must be used when creating a new FileBasedSource for a subrange of a single file. Additionally, this constructor must be used to create new FileBasedSources when subclasses implement the method createForSubrangeOfFile(org.apache.beam.sdk.io.fs.MatchResult.Metadata, long, long).

See OffsetBasedSource for detailed descriptions of minBundleSize, startOffset, and endOffset.

Parameters:

fileMetadata - specification of the file represented by the FileBasedSource, in suitable form for use with FileSystems.match(List).

minBundleSize - minimum bundle size in bytes.

startOffset - starting byte offset.

endOffset - ending byte offset. If the specified value >= #getMaxEndOffset() it implies #getMaxEndOffSet().

Method Detail

getSingleFileMetadata

protected final MatchResult.Metadata getSingleFileMetadata()

Returns the information about the single file that this source is reading from.

Throws:

java.lang.IllegalArgumentException - if this source is in FileBasedSource.Mode.FILEPATTERN mode.

getFileOrPatternSpec

public final java.lang.String getFileOrPatternSpec()

getFileOrPatternSpecProvider

public final ValueProvider<java.lang.String> getFileOrPatternSpecProvider()

getMode

public final FileBasedSource.Mode getMode()

createSourceForSubrange

public final FileBasedSource<T> createSourceForSubrange(long start,
                                                        long end)

Description copied from class: OffsetBasedSource

Returns an OffsetBasedSource for a subrange of the current source. The subrange [start, end) must be within the range [startOffset, endOffset) of the current source, i.e. startOffset <= start < end <= endOffset.

Specified by:

createSourceForSubrange in class OffsetBasedSource<T>

createForSubrangeOfFile

protected abstract FileBasedSource<T> createForSubrangeOfFile(MatchResult.Metadata fileMetadata,
                                                              long start,
                                                              long end)

Creates and returns a new FileBasedSource of the same type as the current FileBasedSource backed by a given file and an offset range. When current source is being split, this method is used to generate new sub-sources. When creating the source subclasses must call the constructor #FileBasedSource(Metadata, long, long, long) of FileBasedSource with corresponding parameter values passed here.

Parameters:

fileMetadata - file backing the new FileBasedSource.

start - starting byte offset of the new FileBasedSource.

end - ending byte offset of the new FileBasedSource. May be Long.MAX_VALUE, in which case it will be inferred using getMaxEndOffset(org.apache.beam.sdk.options.PipelineOptions).

createSingleFileReader

protected abstract FileBasedSource.FileBasedReader<T> createSingleFileReader(PipelineOptions options)

Creates and returns an instance of a FileBasedReader implementation for the current source assuming the source represents a single file. File patterns will be handled by FileBasedSource implementation automatically.

getEstimatedSizeBytes

public final long getEstimatedSizeBytes(PipelineOptions options)
                                 throws java.io.IOException

Description copied from class: BoundedSource

An estimate of the total size (in bytes) of the data that would be read from this source. This estimate is in terms of external storage size, before any decompression or other processing done by the reader.

If there is no way to estimate the size of the source implementations MAY return 0L.

Overrides:

getEstimatedSizeBytes in class OffsetBasedSource<T>

Throws:

java.io.IOException

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Description copied from class: Source

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 OffsetBasedSource<T>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData

split

public final java.util.List<? extends FileBasedSource<T>> split(long desiredBundleSizeBytes,
                                                                PipelineOptions options)
                                                         throws java.lang.Exception

Description copied from class: BoundedSource

Splits the source into bundles of approximately desiredBundleSizeBytes.

Overrides:

split in class OffsetBasedSource<T>

Throws:

java.lang.Exception

isSplittable

protected boolean isSplittable()
                        throws java.lang.Exception

Determines whether a file represented by this source is can be split into bundles.

By default, a source in mode FileBasedSource.Mode.FILEPATTERN is always splittable, because splitting will involve expanding the file pattern and producing single-file/subrange sources, which may or may not be splittable themselves.

By default, a source in FileBasedSource.Mode.SINGLE_FILE_OR_SUBRANGE is splittable if it is on a file system that supports efficient read seeking.

Subclasses may override to provide different behavior.

Throws:

java.lang.Exception

createReader

public final BoundedSource.BoundedReader<T> createReader(PipelineOptions options)
                                                  throws java.io.IOException

Description copied from class: BoundedSource

Returns a new BoundedSource.BoundedReader that reads from this source.

Specified by:

createReader in class BoundedSource<T>

Throws:

java.io.IOException

toString

public java.lang.String toString()

Overrides:

toString in class OffsetBasedSource<T>

validate

public void validate()

Description copied from class: Source

Checks that this source is valid, before it can be used in a pipeline.

It is recommended to use Preconditions for implementing this method.

Overrides:

validate in class OffsetBasedSource<T>

getMaxEndOffset

public final long getMaxEndOffset(PipelineOptions options)
                           throws java.io.IOException

Description copied from class: OffsetBasedSource

Returns the actual ending offset of the current source. The value returned by this function will be used to clip the end of the range [startOffset, endOffset) such that the range used is [startOffset, min(endOffset, maxEndOffset)).

As an example in which OffsetBasedSource is used to implement a file source, suppose that this source was constructed with an endOffset of Long.MAX_VALUE to indicate that a file should be read to the end. Then this function should determine the actual, exact size of the file in bytes and return it.

Specified by:

getMaxEndOffset in class OffsetBasedSource<T>

Throws:

java.io.IOException