@Experimental(value=SPLITTABLE_DO_FN) public class OffsetRangeTracker extends RestrictionTracker<OffsetRange,java.lang.Long> implements RestrictionTracker.HasProgress
RestrictionTracker for claiming offsets in an OffsetRange in a monotonically
increasing fashion.
The smallest offset is Long.MIN_VALUE and the largest offset is Long.MAX_VALUE
- 1.
RestrictionTracker.HasProgress, RestrictionTracker.Progress| Modifier and Type | Field and Description |
|---|---|
protected java.lang.Long |
lastAttemptedOffset |
protected java.lang.Long |
lastClaimedOffset |
protected OffsetRange |
range |
| Constructor and Description |
|---|
OffsetRangeTracker(OffsetRange range) |
| Modifier and Type | Method and Description |
|---|---|
void |
checkDone()
Called by the runner after
DoFn.ProcessElement returns. |
OffsetRange |
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.
|
java.lang.String |
toString() |
boolean |
tryClaim(java.lang.Long i)
Attempts to claim the given offset.
|
SplitResult<OffsetRange> |
trySplit(double fractionOfRemainder)
Splits current restriction based on
fractionOfRemainder. |
protected OffsetRange range
@Nullable protected java.lang.Long lastClaimedOffset
@Nullable protected java.lang.Long lastAttemptedOffset
public OffsetRangeTracker(OffsetRange range)
public OffsetRange currentRestriction()
RestrictionTrackerDoFn.ProcessElement call will do, including already completed work.currentRestriction in class RestrictionTracker<OffsetRange,java.lang.Long>public SplitResult<OffsetRange> 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 required to be implemented for a streaming pipeline.
trySplit in class RestrictionTracker<OffsetRange,java.lang.Long>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(java.lang.Long i)
Must be larger than the last successfully claimed offset.
tryClaim in class RestrictionTracker<OffsetRange,java.lang.Long>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).public void checkDone()
throws java.lang.IllegalStateException
RestrictionTrackerDoFn.ProcessElement returns.
Must throw an exception with an informative error message, if there is still any unclaimed work remaining in the restriction.
checkDone in class RestrictionTracker<OffsetRange,java.lang.Long>java.lang.IllegalStateExceptionpublic 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