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PYTHON-5504 Prototype exponential backoff in with_transaction #2492

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Merged
merged 2 commits into from
Aug 19, 2025
Merged

PYTHON-5504 Prototype exponential backoff in with_transaction #2492

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cec7bc2
DRIVERS-1934 POC exponential backoff in withTransaction
ShaneHarvey Aug 14, 2025
86172fc
PYTHON-5504 Start backoff on first retry not second
ShaneHarvey Aug 19, 2025
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10 changes: 10 additions & 0 deletions pymongo/asynchronous/client_session.py
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Original file line number Diff line number Diff line change
Expand Up @@ -135,7 +135,9 @@

from __future__ import annotations

import asyncio
import collections
import random
import time
import uuid
from collections.abc import Mapping as _Mapping
Expand Down Expand Up @@ -471,6 +473,8 @@ def _max_time_expired_error(exc: PyMongoError) -> bool:
# This limit is non-configurable and was chosen to be twice the 60 second
# default value of MongoDB's `transactionLifetimeLimitSeconds` parameter.
_WITH_TRANSACTION_RETRY_TIME_LIMIT = 120
_BACKOFF_MAX = 1
_BACKOFF_INITIAL = 0.050 # 50ms initial backoff


def _within_time_limit(start_time: float) -> bool:
Expand Down Expand Up @@ -700,7 +704,13 @@ async def callback(session, custom_arg, custom_kwarg=None):
https://github.com/mongodb/specifications/blob/master/source/transactions-convenient-api/transactions-convenient-api.md#handling-errors-inside-the-callback
"""
start_time = time.monotonic()
retry = 0
while True:
if retry: # Implement exponential backoff on retry.
jitter = random.random() # noqa: S311
backoff = jitter * min(_BACKOFF_INITIAL * (2**retry), _BACKOFF_MAX)
await asyncio.sleep(backoff)
retry += 1
await self.start_transaction(
read_concern, write_concern, read_preference, max_commit_time_ms
)
Expand Down
9 changes: 9 additions & 0 deletions pymongo/synchronous/client_session.py
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,7 @@
from __future__ import annotations

import collections
import random
import time
import uuid
from collections.abc import Mapping as _Mapping
Expand Down Expand Up @@ -470,6 +471,8 @@ def _max_time_expired_error(exc: PyMongoError) -> bool:
# This limit is non-configurable and was chosen to be twice the 60 second
# default value of MongoDB's `transactionLifetimeLimitSeconds` parameter.
_WITH_TRANSACTION_RETRY_TIME_LIMIT = 120
_BACKOFF_MAX = 1
_BACKOFF_INITIAL = 0.050 # 50ms initial backoff


def _within_time_limit(start_time: float) -> bool:
Expand Down Expand Up @@ -699,7 +702,13 @@ def callback(session, custom_arg, custom_kwarg=None):
https://github.com/mongodb/specifications/blob/master/source/transactions-convenient-api/transactions-convenient-api.md#handling-errors-inside-the-callback
"""
start_time = time.monotonic()
retry = 0
while True:
if retry: # Implement exponential backoff on retry.
jitter = random.random() # noqa: S311
backoff = jitter * min(_BACKOFF_INITIAL * (2**retry), _BACKOFF_MAX)
time.sleep(backoff)
retry += 1
self.start_transaction(read_concern, write_concern, read_preference, max_commit_time_ms)
try:
ret = callback(self)
Expand Down
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