[Zen2] Elect freshest master in upgrade #37122
Merged
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
DaveCTurner
added
>bug
v7.0.0
:Distributed Coordination/Cluster Coordination
|
Pinging @elastic/es-distributed |
61 tasks
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Outdated suggestions cannot be applied.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.
Today when electing a master in Zen2 we use the cluster state version to
determine whether a node has a fresh-enough cluster state to become master.
However the cluster state version is not a reliable measure of freshness in the
Zen1 world; furthermore in 6.x the cluster state version is not persisted. This
means that when upgrading from 6.x via a full cluster restart a cluster state
update may be lost if a stale master wins the initial election.
This change fixes this by using the metadata version as a measure of freshness
when in term 0, since this is persisted in 6.x and does more reliably indicate
the freshness of nodes.
It also makes changes parallel to elastic/elasticsearch-formal-models#40 to
support situations in which nodes accept cluster state versions in term 0: this
does not happen in a pure Zen2 cluster, but can happen in mixed clusters and
during upgrades.