Loading...

XML

Word

Printable

JSON

Type: Bug
Resolution: Fixed
Priority: Major - P3
Fix Version/s: 4.4.1, 4.7.0
Affects Version/s: None
Component/s: None
Labels:
None

Backwards Compatibility:
Fully Compatible
Operating System:
ALL
Backport Requested:

v4.4
Steps To Reproduce:

Hide

Given an initial topology T0, getHosts request R, and topology change event T that can satisfy R.

0. initial state: T0 cannot satisfy R
1. The RSM receives R concurrent with T.
1a. RSM checks topology and sees T0: https://github.com/mongodb/mongo/blob/23e6f954d7ef5ab73f5540b46c6b3794b7ecfbdc/src/mongo/client/streamable_replica_set_monitor.cpp#L252
2. R is scheduled to be fulfilled async: https://github.com/mongodb/mongo/blob/23e6f954d7ef5ab73f5540b46c6b3794b7ecfbdc/src/mongo/client/streamable_replica_set_monitor.cpp#L257
3. T occurs concurrently with step 2 prior to enqueuing R
4. R is enqueued: https://github.com/mongodb/mongo/blob/23e6f954d7ef5ab73f5540b46c6b3794b7ecfbdc/src/mongo/client/streamable_replica_set_monitor.cpp#L279
5. If no further topology changes occur the query will timeout with FailedToSatisfyReadPreference

Show
Given an initial topology T0, getHosts request R, and topology change event T that can satisfy R. 0. initial state: T0 cannot satisfy R 1. The RSM receives R concurrent with T. 1a. RSM checks topology and sees T0: https://github.com/mongodb/mongo/blob/23e6f954d7ef5ab73f5540b46c6b3794b7ecfbdc/src/mongo/client/streamable_replica_set_monitor.cpp#L252 2. R is scheduled to be fulfilled async: https://github.com/mongodb/mongo/blob/23e6f954d7ef5ab73f5540b46c6b3794b7ecfbdc/src/mongo/client/streamable_replica_set_monitor.cpp#L257 3. T occurs concurrently with step 2 prior to enqueuing R 4. R is enqueued: https://github.com/mongodb/mongo/blob/23e6f954d7ef5ab73f5540b46c6b3794b7ecfbdc/src/mongo/client/streamable_replica_set_monitor.cpp#L279 5. If no further topology changes occur the query will timeout with FailedToSatisfyReadPreference
Sprint:
Service arch 2020-05-04, Service arch 2020-05-18, Sharding 2020-06-29
Linked BF Score:
16

See the steps in "Steps To Reproduce" below.

A fix for this is to invoke server selection at the time of step 4 with a fresh view of the topology while synchronizing with the TopologyManager.

The topology views (and corresponding topology change events) are serialized, so at step 4 we would either see T0 or T and would block any future topology changes while R is being enqueued.

In the first case (we see T0), server selection would return no result, the request would be enqueued, and the query will be satisfied after T is applied to the topology manager.

In the second case (we see T), the query will be satisfied without enqueuing the request.

is depended on by

SERVER-48925 Exclude servers with unknown server description in StreamableRSM's getMinWireVersion and getMaxWireVersion

Closed

Assignee:: Cheahuychou Mao

Reporter:: Lamont Nelson

Participants:: Cheahuychou Mao, Githook User, Lamont Nelson

Votes:: 0 Vote for this issue

Watchers:: 5 Start watching this issue

Created:: Apr 17 2020 06:43:51 PM UTC

Updated:: Oct 29 2023 10:09:18 PM UTC

Resolved:: Jun 23 2020 07:46:03 PM UTC

Details

Description

Attachments

Issue Links

Activity

People

Dates