Wait for DB writes to propagate (causality checks) #392
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Because we deploy the database in multi-master mode we can have cases where a service writes something in the database and when another one reads from the DB that data is not yet there. This is very problematic, because all the cinder code assumes that that can never happen. For example we've seen in CI jobs the following behavior: - Cinder api creates a worker registry in the DB when deleting a volume on DB node #1. - Cinder api makes an RPC call to cinder-volume to delete the volume. - Cinder volume tries to read the worker registry from DB node #2 but the data is not there yet, so it misbehaves. In this patch we change the default value on the DB engine of not waiting for writes to wait on read, update, and insert. This will have a performance impact, but the alternative is for cinder to misbehave. We use `mysql_wsrep_sync_wait` from oslo.db [1] setting it to 7 as per the documented values of this parameter in the DBMS [2][3]. [1]: https://opendev.org/openstack/oslo.db/commit/009d23df45969036c70e4cf59eb4019aaace9a55 [2]: https://mariadb.com/docs/server/ref/mdb/system-variables/wsrep_sync_wait/ [3]: https://galeracluster.com/library/documentation/mysql-wsrep-options.html
|
@Akrog: The following test failed, say
Full PR test history. Your PR dashboard. Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here. |
zzzeek
approved these changes
May 29, 2024
|
[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: Akrog, zzzeek The full list of commands accepted by this bot can be found here. The pull request process is described here
Needs approval from an approver in each of these files:
Approvers can indicate their approval by writing |
openshift-merge-bot
bot
merged commit 658ff9a
into
openstack-k8s-operators:main
6 of 7 checks passed
gthiemonge
added a commit
to gthiemonge/octavia-operator
that referenced
this pull request
May 29, 2024
Fix some inconsistencies in multi-master mode (based on openstack-k8s-operators/cinder-operator#392) Jira: OSPRH-7369
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Because we deploy the database in multi-master mode we can have cases where a service writes something in the database and when another one reads from the DB that data is not yet there.
This is very problematic, because all the cinder code assumes that that can never happen.
For example we've seen in CI jobs the following behavior:
Cinder api creates a worker registry in the DB when deleting a volume on DB node 1.
Cinder api makes an RPC call to cinder-volume to delete the volume.
Cinder volume tries to read the worker registry from DB node 2 but the data is not there yet, so it misbehaves.
In this patch we change the default value on the DB engine of not waiting for writes to wait on read, update, and insert.
This will have a performance impact, but the alternative is for cinder to misbehave.
We use
mysql_wsrep_sync_waitfrom oslo.db 1 setting it to 7 as per the documented values of this parameter in the DBMS 2 3.