rabbit_peer_discovery: Cache computed node start time #13128
Closed
Conversation
This file contains hidden or 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
[Why] The computation of a node's system-time-based start time is based on its monotonic-time-based start time plus the current time offset. However, since Erlang/OTP 26, that time offset is volatile by default. Therefore the computed system-time-based start time can change too. It happens in CI and this affects the seed node selection in the peer discovery code: because the sorting is unstable when the start time is the criteria, different instances of the peen discovery code could select a different node. [How] The same code is used to compute the start time. However, the computed value is cached in a persistent_term for future queries. This way we ensure that the value is computed once and thus all queries will return the same result.
dumbbell
force-pushed
the
fix-peer-disc-node-sorting-with-erlang26
branch
from
0d89189 to
3dd8a24
Compare
Collaborator
Author
|
Superseeded by #13490. |
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Outdated suggestions cannot be applied.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.
Why
The computation of a node's system-time-based start time is based on its monotonic-time-based start time plus the current time offset.
However, since Erlang/OTP 26, that time offset is volatile by default. Therefore the computed system-time-based start time can change too. It happens in CI and this affects the seed node selection in the peer discovery code: because the sorting is unstable when the start time is the criteria, different instances of the peen discovery code could select a different node.
How
The same code is used to compute the start time. However, the computed value is cached in a persistent_term for future queries. This way we ensure that the value is computed once and thus all queries will return the same result.