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https://issues.apache.org/jira/browse/BEAM-8537?focusedWorklogId=371219&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-371219
]
ASF GitHub Bot logged work on BEAM-8537:
----------------------------------------
Author: ASF GitHub Bot
Created on: 13/Jan/20 23:59
Start Date: 13/Jan/20 23:59
Worklog Time Spent: 10m
Work Description: lukecwik commented on pull request #10375: [BEAM-8537]
Provide WatermarkEstimator to track watermark
URL: https://github.com/apache/beam/pull/10375#discussion_r366086655
##########
File path: sdks/python/apache_beam/io/iobase.py
##########
@@ -1236,127 +1233,38 @@ def try_claim(self, position):
raise NotImplementedError
-class ThreadsafeRestrictionTracker(object):
- """A thread-safe wrapper which wraps a `RestritionTracker`.
+class WatermarkEstimator(object):
+ """A WatermarkEstimator which is used for estimating output_watermark based
on
+ the timestamp of output records or manual modifications.
- This wrapper guarantees synchronization of modifying restrictions across
- multi-thread.
- """
-
- def __init__(self, restriction_tracker):
- if not isinstance(restriction_tracker, RestrictionTracker):
- raise ValueError(
- 'Initialize ThreadsafeRestrictionTracker requires'
- 'RestrictionTracker.')
- self._restriction_tracker = restriction_tracker
- # Records an absolute timestamp when defer_remainder is called.
- self._deferred_timestamp = None
- self._lock = threading.RLock()
- self._deferred_residual = None
- self._deferred_watermark = None
-
- def current_restriction(self):
- with self._lock:
- return self._restriction_tracker.current_restriction()
-
- def try_claim(self, position):
- with self._lock:
- return self._restriction_tracker.try_claim(position)
-
- def defer_remainder(self, deferred_time=None):
- """Performs self-checkpoint on current processing restriction with an
- expected resuming time.
+ The base class provides common APIs that are called by the framework, which
+ are also accessible inside a DoFn.process() body. Derived watermark estimator
+ should implement all APIs listed below. Additional methods can be implemented
+ and will be available when invoked within a DoFn.
- Self-checkpoint could happen during processing elements. When executing an
- DoFn.process(), you may want to stop processing an element and resuming
- later if current element has been processed quit a long time or you also
- want to have some outputs from other elements. ``defer_remainder()`` can be
- called on per element if needed.
-
- Args:
- deferred_time: A relative ``timestamp.Duration`` that indicates the ideal
- time gap between now and resuming, or an absolute ``timestamp.Timestamp``
- for resuming execution time. If the time_delay is None, the deferred work
- will be executed as soon as possible.
+ Multi-threading safety is guarded by ThreadsafeWatermarkEstimator.
+ """
+ def get_estimator_state(self):
+ """Get current state of the WatermarkEstimator instance, which can be used
+ to recreate the WatermarkEstimator when processing the restriction. See
+ WatermarkEstimatorProvider.create_watermark_estimator.
"""
+ raise NotImplementedError(type(self))
- # Record current time for calculating deferred_time later.
- self._deferred_timestamp = timestamp.Timestamp.now()
- if (deferred_time and
- not isinstance(deferred_time, timestamp.Duration) and
- not isinstance(deferred_time, timestamp.Timestamp)):
- raise ValueError('The timestamp of deter_remainder() should be a '
- 'Duration or a Timestamp, or None.')
- self._deferred_watermark = deferred_time
- checkpoint = self.try_split(0)
- if checkpoint:
- _, self._deferred_residual = checkpoint
-
- def check_done(self):
- with self._lock:
- return self._restriction_tracker.check_done()
-
- def current_progress(self):
- with self._lock:
- return self._restriction_tracker.current_progress()
-
- def try_split(self, fraction_of_remainder):
- with self._lock:
- return self._restriction_tracker.try_split(fraction_of_remainder)
+ def current_watermark(self):
+ """Return estimated output_watermark. This function must return
+ monotonically increasing watermark."""
Review comment:
```suggestion
monotonically increasing watermarks."""
```
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Issue Time Tracking
-------------------
Worklog Id: (was: 371219)
Time Spent: 3h 50m (was: 3h 40m)
> Provide WatermarkEstimatorProvider for different types of WatermarkEstimator
> ----------------------------------------------------------------------------
>
> Key: BEAM-8537
> URL: https://issues.apache.org/jira/browse/BEAM-8537
> Project: Beam
> Issue Type: Improvement
> Components: sdk-py-core, sdk-py-harness
> Reporter: Boyuan Zhang
> Assignee: Boyuan Zhang
> Priority: Major
> Time Spent: 3h 50m
> Remaining Estimate: 0h
>
> This is a follow up for in-progress PR:
> https://github.com/apache/beam/pull/9794.
> Current implementation in PR9794 provides a default implementation of
> WatermarkEstimator. For further work, we want to let WatermarkEstimator to be
> a pure Interface. We'll provide a WatermarkEstimatorProvider to be able to
> create a custom WatermarkEstimator per windowed value. It should be similar
> to how we track restriction for SDF:
> WatermarkEstimator <---> RestrictionTracker
> WatermarkEstimatorProvider <---> RestrictionTrackerProvider
> WatermarkEstimatorParam <---> RestrictionDoFnParam
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