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https://issues.apache.org/jira/browse/BEAM-8537?focusedWorklogId=390820&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-390820
]
ASF GitHub Bot logged work on BEAM-8537:
----------------------------------------
Author: ASF GitHub Bot
Created on: 21/Feb/20 18:10
Start Date: 21/Feb/20 18:10
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_r382723627
##########
File path: sdks/python/apache_beam/io/watermark_estimators.py
##########
@@ -0,0 +1,150 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+"""A collection of WatermarkEstimator implementations that SplittableDoFns
+can use."""
+
+# pytype: skip-file
+
+from __future__ import absolute_import
+
+from apache_beam.io.iobase import WatermarkEstimator
+from apache_beam.transforms.core import WatermarkEstimatorProvider
+from apache_beam.utils.timestamp import Timestamp
+
+
+class MonotonicWatermarkEstimator(WatermarkEstimator):
+ """A WatermarkEstimator which assumes that timestamps of all ouput records
+ are increasing monotonically.
+ """
+ def __init__(self, timestamp):
+ """For a new <element, restriction> pair, the initial value is None. When
+ resuming processing, the initial timestamp will be the last reported
+ watermark.
+ """
+ self._watermark = timestamp
+
+ def observe_timestamp(self, timestamp):
+ if self._watermark is None:
+ self._watermark = timestamp
+ else:
+ # TODO(BEAM-9312): Consider making it configurable to deal with late
+ # timestamp.
+ if timestamp < self._watermark:
+ raise ValueError(
+ 'A MonotonicWatermarkEstimator expects output '
+ 'timestamp to be increasing monotonically.')
+ self._watermark = timestamp
+
+ def current_watermark(self):
+ return self._watermark
+
+ def get_estimator_state(self):
+ return self._watermark
+
+ @staticmethod
+ def default_provider():
+ """Provide a default WatermarkEstimatorProvider for
+ MonotonicWatermarkEstimator.
+ """
+ class DefaultMonotonicWatermarkEstimator(WatermarkEstimatorProvider):
+ def initial_estimator_state(self, element, restriction):
+ return None
+
+ def create_watermark_estimator(self, estimator_state):
+ return MonotonicWatermarkEstimator(estimator_state)
+
+ return DefaultMonotonicWatermarkEstimator()
+
+
+class WalltimeWatermarkEstimator(WatermarkEstimator):
+ """A WatermarkEstimator which uses processing time as the estimated
watermark.
+ """
+ def __init__(self, timestamp=None):
+ self._timestamp = timestamp or Timestamp.now()
+
+ def observe_timestamp(self, timestamp):
+ pass
+
+ def current_watermark(self):
+ self._timestamp = max(self._timestamp, Timestamp.now())
+ return self._timestamp
+
+ def get_estimator_state(self):
+ return self._timestamp
+
+ @staticmethod
+ def default_provider():
+ """Provide a default WatermarkEstimatorProvider for
+ WalltimeWatermarkEstimator.
+ """
+ class DefaultWalltimeWatermarkEstimator(WatermarkEstimatorProvider):
+ def initial_estimator_state(self, element, restriction):
+ return None
+
+ def create_watermark_estimator(self, estimator_state):
+ return WalltimeWatermarkEstimator(estimator_state)
+
+ return DefaultWalltimeWatermarkEstimator()
+
+
+class ManualWatermarkEstimator(WatermarkEstimator):
+ """A WatermarkEstimator which is controlled manually from within a DoFn.
+
+ The DoFn must invoke set_watermark to advance the watermark.
+ """
+ def __init__(self, watermark):
+ self._watermark = watermark
+
+ def observe_timestamp(self, timestamp):
+ pass
+
+ def current_watermark(self):
+ return self._watermark
+
+ def get_estimator_state(self):
+ return self._watermark
+
+ def set_watermark(self, timestamp):
+ # Please call set_watermark after calling restriction_tracker.try_claim()
to
+ # prevent advancing watermark early.
+ # TODO(BEAM-7473): It's possible that getting a slightly stale watermark
Review comment:
I would drop the TODO and close the JIRA since we can't reliably resolve it
with how our APIs are setup since try_claim needs to advance the watermark at
the same time.
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Issue Time Tracking
-------------------
Worklog Id: (was: 390820)
Time Spent: 17h (was: 16h 50m)
> 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: 17h
> 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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