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PYTHON-2970 Prioritize electionId over setVersion for stale primary check on 6.0+ #1067

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Merged
merged 2 commits into from
Oct 5, 2022
Merged

PYTHON-2970 Prioritize electionId over setVersion for stale primary check on 6.0+ #1067

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PYTHON-2970 Prioritize electionId over setVersion for stale primary c…
ShaneHarvey Mar 9, 2022
f513533
PYTHON-3400 Only use new electionId/setVersion logic on 6.0+
ShaneHarvey Sep 29, 2022
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3 changes: 3 additions & 0 deletions doc/changelog.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,8 @@ Bug fixes
- Fixed a bug where :class:`~pymongo.change_stream.ChangeStream`
would allow an app to retry calling ``next()`` or ``try_next()`` even
after non-resumable errors (`PYTHON-3389`_).
- Fixed a bug where the client could be unable to discover the new primary
after a simultaneous replica set election and reconfig (`PYTHON-2970`_).

Issues Resolved
...............
Expand All @@ -42,6 +44,7 @@ in this release.

.. _PYTHON-1824: https://jira.mongodb.org/browse/PYTHON-1824
.. _PYTHON-2484: https://jira.mongodb.org/browse/PYTHON-2484
.. _PYTHON-2970: https://jira.mongodb.org/browse/PYTHON-2970
.. _PYTHON-3389: https://jira.mongodb.org/browse/PYTHON-3389
.. _PyMongo 4.3 release notes in JIRA: https://jira.mongodb.org/secure/ReleaseNote.jspa?projectId=10004&version=33425

Expand Down
43 changes: 26 additions & 17 deletions pymongo/topology_description.py
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
from random import sample
from typing import Any, Callable, Dict, List, NamedTuple, Optional, Tuple

from bson.min_key import MinKey
from bson.objectid import ObjectId
from pymongo import common
from pymongo.errors import ConfigurationError
Expand Down Expand Up @@ -530,26 +531,34 @@ def _update_rs_from_primary(
# We found a primary but it doesn't have the replica_set_name
# provided by the user.
sds.pop(server_description.address)
return (_check_has_primary(sds), replica_set_name, max_set_version, max_election_id)

max_election_tuple = max_set_version, max_election_id
if None not in server_description.election_tuple:
if (
None not in max_election_tuple
and max_election_tuple > server_description.election_tuple
return _check_has_primary(sds), replica_set_name, max_set_version, max_election_id

if server_description.max_wire_version is None or server_description.max_wire_version < 17:
new_election_tuple = server_description.set_version, server_description.election_id
max_election_tuple = max_set_version, max_election_id
if None not in new_election_tuple:
if None not in max_election_tuple and new_election_tuple < max_election_tuple:
# Stale primary, set to type Unknown.
sds[server_description.address] = server_description.to_unknown()
return _check_has_primary(sds), replica_set_name, max_set_version, max_election_id
max_election_id = server_description.election_id

if server_description.set_version is not None and (
max_set_version is None or server_description.set_version > max_set_version
):

max_set_version = server_description.set_version
else:
new_election_tuple = server_description.election_id, server_description.set_version
max_election_tuple = max_election_id, max_set_version
new_election_safe = tuple(MinKey() if i is None else i for i in new_election_tuple)
max_election_safe = tuple(MinKey() if i is None else i for i in max_election_tuple)
if new_election_safe < max_election_safe:
# Stale primary, set to type Unknown.
sds[server_description.address] = server_description.to_unknown()
return (_check_has_primary(sds), replica_set_name, max_set_version, max_election_id)

max_election_id = server_description.election_id

if server_description.set_version is not None and (
max_set_version is None or server_description.set_version > max_set_version
):

max_set_version = server_description.set_version
return _check_has_primary(sds), replica_set_name, max_set_version, max_election_id
else:
max_election_id = server_description.election_id
max_set_version = server_description.set_version

# We've heard from the primary. Is it the same primary as before?
for server in sds.values():
Expand Down
92 changes: 92 additions & 0 deletions test/discovery_and_monitoring/rs/electionId_precedence_setVersion.json
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@@ -0,0 +1,92 @@
{
"description": "ElectionId is considered higher precedence than setVersion",
"uri": "mongodb://a/?replicaSet=rs",
"phases": [
{
"responses": [
[
"a:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017"
],
"setName": "rs",
"setVersion": 1,
"electionId": {
"$oid": "000000000000000000000001"
},
"minWireVersion": 0,
"maxWireVersion": 17
}
],
[
"b:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017"
],
"setName": "rs",
"setVersion": 2,
"electionId": {
"$oid": "000000000000000000000001"
},
"minWireVersion": 0,
"maxWireVersion": 17
}
],
[
"a:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017"
],
"setName": "rs",
"setVersion": 1,
"electionId": {
"$oid": "000000000000000000000002"
},
"minWireVersion": 0,
"maxWireVersion": 17
}
]
],
"outcome": {
"servers": {
"a:27017": {
"type": "RSPrimary",
"setName": "rs",
"setVersion": 1,
"electionId": {
"$oid": "000000000000000000000002"
}
},
"b:27017": {
"type": "Unknown",
"setName": null,
"setVersion": null,
"electionId": null
}
},
"topologyType": "ReplicaSetWithPrimary",
"logicalSessionTimeoutMinutes": null,
"setName": "rs",
"maxSetVersion": 1,
"maxElectionId": {
"$oid": "000000000000000000000002"
}
}
}
]
}
203 changes: 203 additions & 0 deletions test/discovery_and_monitoring/rs/null_election_id-pre-6.0.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,203 @@
{
"description": "Pre 6.0 Primaries with and without electionIds",
"uri": "mongodb://a/?replicaSet=rs",
"phases": [
{
"responses": [
[
"a:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017",
"c:27017"
],
"setVersion": 1,
"setName": "rs",
"minWireVersion": 0,
"maxWireVersion": 6
}
]
],
"outcome": {
"servers": {
"a:27017": {
"type": "RSPrimary",
"setName": "rs",
"setVersion": 1,
"electionId": null
},
"b:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
},
"c:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
}
},
"topologyType": "ReplicaSetWithPrimary",
"logicalSessionTimeoutMinutes": null,
"setName": "rs",
"maxSetVersion": 1
}
},
{
"responses": [
[
"b:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017",
"c:27017"
],
"setName": "rs",
"setVersion": 1,
"electionId": {
"$oid": "000000000000000000000002"
},
"minWireVersion": 0,
"maxWireVersion": 6
}
]
],
"outcome": {
"servers": {
"a:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
},
"b:27017": {
"type": "RSPrimary",
"setName": "rs",
"setVersion": 1,
"electionId": {
"$oid": "000000000000000000000002"
}
},
"c:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
}
},
"topologyType": "ReplicaSetWithPrimary",
"logicalSessionTimeoutMinutes": null,
"setName": "rs",
"maxSetVersion": 1,
"maxElectionId": {
"$oid": "000000000000000000000002"
}
}
},
{
"responses": [
[
"a:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017",
"c:27017"
],
"setVersion": 1,
"setName": "rs",
"minWireVersion": 0,
"maxWireVersion": 6
}
]
],
"outcome": {
"servers": {
"a:27017": {
"type": "RSPrimary",
"setName": "rs",
"setVersion": 1,
"electionId": null
},
"b:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
},
"c:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
}
},
"topologyType": "ReplicaSetWithPrimary",
"logicalSessionTimeoutMinutes": null,
"setName": "rs",
"maxSetVersion": 1,
"maxElectionId": {
"$oid": "000000000000000000000002"
}
}
},
{
"responses": [
[
"c:27017",
{
"ok": 1,
"helloOk": true,
"isWritablePrimary": true,
"hosts": [
"a:27017",
"b:27017",
"c:27017"
],
"setName": "rs",
"setVersion": 1,
"electionId": {
"$oid": "000000000000000000000001"
},
"minWireVersion": 0,
"maxWireVersion": 6
}
]
],
"outcome": {
"servers": {
"a:27017": {
"type": "RSPrimary",
"setName": "rs",
"setVersion": 1,
"electionId": null
},
"b:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
},
"c:27017": {
"type": "Unknown",
"setName": null,
"electionId": null
}
},
"topologyType": "ReplicaSetWithPrimary",
"logicalSessionTimeoutMinutes": null,
"setName": "rs",
"maxSetVersion": 1,
"maxElectionId": {
"$oid": "000000000000000000000002"
}
}
}
]
}
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