[GitHub] [beam] nehsyc commented on a change in pull request #14723: [BEAM-12272] Python - Backport Firestore connector's ramp-up throttling to Datastore connector

[GitBox <gi...@apache.org>]

nehsyc commented on a change in pull request #14723:
URL: https://github.com/apache/beam/pull/14723#discussion_r643459194



##########
File path: sdks/python/apache_beam/io/gcp/datastore/v1new/rampup_throttling_fn.py
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@@ -0,0 +1,80 @@
+import datetime
+import logging
+import time
+from typing import TypeVar
+
+from apache_beam import typehints
+from apache_beam.io.gcp.datastore.v1new import util
+from apache_beam.transforms import DoFn
+from apache_beam.utils.retry import FuzzedExponentialIntervals
+
+T = TypeVar('T')
+
+_LOG = logging.getLogger(__name__)
+
+
+@typehints.with_input_types(T)
+@typehints.with_output_types(T)
+class RampupThrottlingFn(DoFn):
+  """A ``DoFn`` that throttles ramp-up following an exponential function.
+
+  An implementation of a client-side throttler that enforces a gradual ramp-up,
+  broadly in line with Datastore best practices. See also
+  https://cloud.google.com/datastore/docs/best-practices#ramping_up_traffic.
+  """
+  def to_runner_api_parameter(self, unused_context):
+    from apache_beam.internal import pickler
+    config = {
+        'num_workers': self._num_workers,
+    }
+    return 'beam:fn:rampup_throttling:v0', pickler.dumps(config)
+
+  _BASE_BUDGET = 500
+  _RAMP_UP_INTERVAL = datetime.timedelta(minutes=5)
+
+  def __init__(self, num_workers, *unused_args, **unused_kwargs):
+    """Initializes a ramp-up throttler transform.
+
+     Args:
+       num_workers: A hint for the expected number of workers, used to derive
+                    the local rate limit.
+     """
+    super(RampupThrottlingFn, self).__init__(*unused_args, **unused_kwargs)
+    self._num_workers = num_workers
+    self._successful_ops = util.MovingSum(window_ms=1000, bucket_ms=1000)
+    self._first_instant = datetime.datetime.now()
+
+  def _calc_max_ops_budget(
+      self,
+      first_instant: datetime.datetime,
+      current_instant: datetime.datetime):
+    """Function that returns per-second budget according to best practices.
+
+    The exact function is `500 / num_shards * 1.5^max(0, (x-5)/5)`, where x is

Review comment:
       nit: num_workers to align with the variable name




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