@Experimental(value=SPLITTABLE_DO_FN) public class GrowableOffsetRangeTracker extends OffsetRangeTracker
OffsetRangeTrackerfor tracking a growable offset range.
Long.MAX_VALUEis used as the end of the range to indicate infinity.
An offset range is considered growable when the end offset could grow (or change) during execution time (e.g., Kafka topic partition offset, appended file, ...).
The growable range is marked as done by claiming
|Modifier and Type||Class and Description|
Provides the estimated end offset of the range.
|Constructor and Description|
|Modifier and Type||Method and Description|
A representation for the amount of known completed and known remaining work.
Splits current restriction based on
checkDone, currentRestriction, toString, tryClaim
public GrowableOffsetRangeTracker(long start, GrowableOffsetRangeTracker.RangeEndEstimator rangeEndEstimator)
public SplitResult<OffsetRange> trySplit(double fractionOfRemainder)
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
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.
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
0.7, the primary and residual restrictions returned would be
[100, 179), [179, 200)
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.
fractionOfRemainder- A hint as to the fraction of work the primary restriction should represent based upon the current known remaining amount of work.
SplitResultif a split was possible, otherwise returns
null. If the
fractionOfRemainder == 0, a
nullresult MUST imply that the restriction tracker is done and there is no more work left to do.
public RestrictionTracker.Progress getProgress()
It is up to each restriction tracker to convert between their natural representation of
completed and remaining work and the
double representation. For example:
message bytesthat have processed and the number of messages or number of
message bytesthat 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.