org.apache.beam.sdk.transforms.splittabledofn

Class OffsetRangeTracker

java.lang.Object

org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker<OffsetRange,java.lang.Long>

org.apache.beam.sdk.transforms.splittabledofn.OffsetRangeTracker

All Implemented Interfaces:

Sizes.HasSize

public class OffsetRangeTracker
extends RestrictionTracker<OffsetRange,java.lang.Long>
implements Sizes.HasSize

A RestrictionTracker for claiming offsets in an OffsetRange in a monotonically increasing fashion.

Constructor Summary

Constructors

Constructor and Description
OffsetRangeTracker(OffsetRange range)

Method Summary

Modifier and Type	Method and Description
void	checkDone() Called by the runner after DoFn.ProcessElement returns.
OffsetRange	checkpoint() Signals that the current DoFn.ProcessElement call should terminate as soon as possible: after this method returns, the tracker MUST refuse all future claim calls, and RestrictionTracker.checkDone() MUST succeed.
OffsetRange	currentRestriction() Returns a restriction accurately describing the full range of work the current DoFn.ProcessElement call will do, including already completed work.
double	getSize() A representation for the amount of known work represented as a size.
java.lang.String	toString()
boolean	tryClaim(java.lang.Long i) Attempts to claim the given offset.

Methods inherited from class java.lang.Object

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

Constructor Detail

OffsetRangeTracker

public OffsetRangeTracker(OffsetRange range)

Method Detail

currentRestriction

public OffsetRange currentRestriction()

Description copied from class: RestrictionTracker

Returns a restriction accurately describing the full range of work the current DoFn.ProcessElement call will do, including already completed work.

Specified by:

currentRestriction in class RestrictionTracker<OffsetRange,java.lang.Long>

checkpoint

public OffsetRange checkpoint()

Description copied from class: RestrictionTracker

Signals that the current DoFn.ProcessElement call should terminate as soon as possible: after this method returns, the tracker MUST refuse all future claim calls, and RestrictionTracker.checkDone() MUST succeed.

Modifies RestrictionTracker.currentRestriction(). Returns a restriction representing the rest of the work: the old value of RestrictionTracker.currentRestriction() is equivalent to the new value and the return value of this method combined.

Must be called at most once on a given object.

Specified by:

checkpoint in class RestrictionTracker<OffsetRange,java.lang.Long>

tryClaim

public boolean tryClaim(java.lang.Long i)

Attempts to claim the given offset.

Must be larger than the last successfully claimed offset.

Specified by:

tryClaim in class RestrictionTracker<OffsetRange,java.lang.Long>

Returns:

true if the offset was successfully claimed, false if it is outside the current OffsetRange of this tracker (in that case this operation is a no-op).

checkDone

public void checkDone()
               throws java.lang.IllegalStateException

Description copied from class: RestrictionTracker

Called by the runner after DoFn.ProcessElement returns.

Must throw an exception with an informative error message, if there is still any unclaimed work remaining in the restriction.

Specified by:

checkDone in class RestrictionTracker<OffsetRange,java.lang.Long>

Throws:

java.lang.IllegalStateException

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

getSize

public double getSize()

Description copied from interface: Sizes.HasSize

A representation for the amount of known work represented as a size. Size double representations should preferably represent a linear space and be comparable within the same partition.

It is up to each restriction tracker to convert between their natural representation of outstanding work and this representation. For example:

• Block based file source (e.g. Avro): From the end of the current block, the remaining number of bytes to the end of the restriction.
• Pull based queue based source (e.g. Pubsub): The local/global size available in number of messages or number of message bytes that have not been processed.
• Key range based source (e.g. Shuffle, Bigtable, ...): Scale the start key to be one and end key to be zero and interpolate the position of the next splittable key as the size. If information about the probability density function or cumulative distribution function is available, size interpolation can be improved. Alternatively, if the number of encoded bytes for the keys and values is known for the key range, the number of remaining bytes can be used.

DoFns should provide a method annotated with DoFn.GetPartition to report a partition identifier if the element and restriction represent the size for a shared resource such as a message queue topic. See DoFn.GetPartition for additional details.

Specified by:

getSize in interface Sizes.HasSize