public class ByteKeyRangeTracker extends RestrictionTracker<ByteKeyRange,ByteKey> implements RestrictionTracker.HasProgress
RestrictionTracker for claiming ByteKeys in a ByteKeyRange in a
monotonically increasing fashion. The range is a semi-open bounded interval [startKey, endKey)
where the limits are both represented by ByteKey.EMPTY.
Note, one can complete a range by claiming the ByteKey.EMPTY once one runs out of keys
to process.
RestrictionTracker.HasProgress, RestrictionTracker.IsBounded, RestrictionTracker.Progress, RestrictionTracker.TruncateResult<RestrictionT>| Modifier and Type | Method and Description |
|---|---|
void |
checkDone()
Checks whether the restriction has been fully processed.
|
ByteKeyRange |
currentRestriction()
Returns a restriction accurately describing the full range of work the current
DoFn.ProcessElement call will do, including already completed work. |
RestrictionTracker.Progress |
getProgress()
A representation for the amount of known completed and known remaining work.
|
RestrictionTracker.IsBounded |
isBounded()
Return the boundedness of the current restriction.
|
static ByteKeyRangeTracker |
of(ByteKeyRange range) |
java.lang.String |
toString() |
boolean |
tryClaim(ByteKey key)
Attempts to claim the given key.
|
SplitResult<ByteKeyRange> |
trySplit(double fractionOfRemainder)
Splits current restriction based on
fractionOfRemainder. |
public static ByteKeyRangeTracker of(ByteKeyRange range)
public ByteKeyRange currentRestriction()
RestrictionTrackerDoFn.ProcessElement call will do, including already completed work.
The current restriction returned by method may be updated dynamically due to due to
concurrent invocation of other methods of the RestrictionTracker, For example, RestrictionTracker.trySplit(double).
This method is required to be implemented.
currentRestriction in class RestrictionTracker<ByteKeyRange,ByteKey>public SplitResult<ByteKeyRange> trySplit(double fractionOfRemainder)
RestrictionTrackerfractionOfRemainder.
If splitting the current restriction is possible, the current restriction is split into a
primary and residual restriction pair. This invocation updates the RestrictionTracker.currentRestriction() to be the primary restriction effectively having the current DoFn.ProcessElement execution responsible for performing the work that the primary restriction
represents. The residual restriction will be executed in a separate DoFn.ProcessElement
invocation (likely in a different process). The work performed by executing the primary and
residual restrictions as separate DoFn.ProcessElement invocations MUST be equivalent to
the work performed as if this split never occurred.
The fractionOfRemainder should be used in a best effort manner to choose a primary
and residual restriction based upon the fraction of the remaining work that the current DoFn.ProcessElement invocation is responsible for. For example, if a DoFn.ProcessElement was reading a file with a restriction representing the offset range [100, 200) and has processed up to offset 130 with a fractionOfRemainder of 0.7, the primary and residual restrictions returned would be [100, 179), [179, 200)
(note: currentOffset + fractionOfRemainder * remainingWork = 130 + 0.7 * 70 = 179).
fractionOfRemainder = 0 means a checkpoint is required.
The API is recommended to be implemented for a batch pipeline to improve parallel processing performance.
The API is recommended to be implemented for batch pipeline given that it is very important for pipeline scaling and end to end pipeline execution.
The API is required to be implemented for a streaming pipeline.
trySplit in class RestrictionTracker<ByteKeyRange,ByteKey>fractionOfRemainder - A hint as to the fraction of work the primary restriction should
represent based upon the current known remaining amount of work.SplitResult if a split was possible, otherwise returns null. If the
fractionOfRemainder == 0, a null result MUST imply that the restriction
tracker is done and there is no more work left to do.public boolean tryClaim(ByteKey key)
Must be larger than the last attempted key. Since this restriction tracker represents a
range over a semi-open bounded interval [start, end), the last key that was attempted
may have failed but still have consumed the interval [lastAttemptedKey, end) since this
range tracker processes keys in a monotonically increasing order. Note that passing in ByteKey.EMPTY claims all keys to the end of range and can only be claimed once.
tryClaim in class RestrictionTracker<ByteKeyRange,ByteKey>true if the key was successfully claimed, false if it is outside the
current ByteKeyRange of this tracker.public void checkDone()
throws java.lang.IllegalStateException
RestrictionTrackerCalled by the SDK harness after DoFn.ProcessElement returns.
Must throw an exception with an informative error message, if there is still any unclaimed work remaining in the restriction.
This method is required to be implemented in order to prevent data loss during SDK processing.
checkDone in class RestrictionTracker<ByteKeyRange,ByteKey>java.lang.IllegalStateExceptionpublic RestrictionTracker.IsBounded isBounded()
RestrictionTrackerRestrictionTracker.IsBounded.BOUNDED. Otherwise, it should return
RestrictionTracker.IsBounded.UNBOUNDED.
It is valid to return RestrictionTracker.IsBounded.BOUNDED after returning RestrictionTracker.IsBounded.UNBOUNDED
once the end of a restriction is discovered. It is not valid to return RestrictionTracker.IsBounded.UNBOUNDED after returning RestrictionTracker.IsBounded.BOUNDED.
This method is required to be implemented.
isBounded in class RestrictionTracker<ByteKeyRange,ByteKey>public java.lang.String toString()
toString in class java.lang.Objectpublic RestrictionTracker.Progress getProgress()
RestrictionTracker.HasProgressIt is up to each restriction tracker to convert between their natural representation of
completed and remaining work and the double representation. For example:
message bytes that have processed and the number of
messages or number of message bytes that are outstanding.
The work completed and work remaining must be of the same scale whether that be number of messages or number of bytes and should never represent two distinct unit types.
getProgress in interface RestrictionTracker.HasProgress