Step down as master when configured out of voting configuration #37802
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ywelsch
added
>enhancement
v7.0.0
:Distributed Coordination/Cluster Coordination
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Pinging @elastic/es-distributed |
DaveCTurner
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Jan 24, 2019
server/src/test/java/org/elasticsearch/cluster/coordination/PublicationTests.java
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DaveCTurner
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Jan 24, 2019
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This required more changes, I'll need another review. |
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DaveCTurner
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Jan 28, 2019
| @@ -162,4 +167,12 @@ public VotingConfiguration reconfigure(Set<DiscoveryNode> liveNodes, Set<String> | |||
| return currentConfig; | |||
| } | |||
| } | |||
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| private TreeSet<String> masterFirstTreeSet(Collection<? extends String> items, DiscoveryNode masterNode) { | |||
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We already have a mechanism for giving nodes different priorities when picking the new configuration:
Stream.of(nonRetiredInConfigLiveIds, nonRetiredLiveNotInConfigIds, nonRetiredInConfigNotLiveIds)
I think I'd prefer having a singleton/empty set containing the master (if it is non-retired/retired respectively) and say
Stream.of(nonRetiredMaster, nonRetiredInConfigLiveIds, nonRetiredLiveNotInConfigIds, nonRetiredInConfigNotLiveIds)
I'd also be happy doing the whole thing with a single treeset.
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I've pushed 4e5886c
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@elasticmachine retest this please |
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@elasticmachine run elasticsearch-ci/default-distro |
DaveCTurner
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Jun 14, 2019
Today we suppress election attempts on master-eligible nodes that are not in the voting configuration. In fact this restriction is not necessary: any master-eligible node can safely become master as long as it has a fresh enough cluster state and can gather a quorum of votes. Moreover, this restriction is sometimes undesirable: there may be a reason why we do not want any of the nodes in the voting configuration to become master. The reason for this restriction is as follows. If you want to shut the master down then you might first exclude it from the voting configuration. When this exclusion succeeds you might reasonably expect that a new master has been elected, since the voting config exclusion is almost always a step towards shutting the node down. If we allow nodes outside the voting configuration to be the master then the excluded node will continue to be master, which is confusing. This commit adjusts the logic to allow master-eligible nodes to attempt an election even if they are not in the voting configuration. If such a master is successfully elected then it adds itself to the voting configuration. This commit also adjusts the logic that causes master nodes to abdicate when they are excluded from the voting configuration, to avoid the confusion described above. Relates elastic#37712, elastic#37802.
DaveCTurner
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Jun 18, 2019
Today we suppress election attempts on master-eligible nodes that are not in the voting configuration. In fact this restriction is not necessary: any master-eligible node can safely become master as long as it has a fresh enough cluster state and can gather a quorum of votes. Moreover, this restriction is sometimes undesirable: there may be a reason why we do not want any of the nodes in the voting configuration to become master. The reason for this restriction is as follows. If you want to shut the master down then you might first exclude it from the voting configuration. When this exclusion succeeds you might reasonably expect that a new master has been elected, since the voting config exclusion is almost always a step towards shutting the node down. If we allow nodes outside the voting configuration to be the master then the excluded node will continue to be master, which is confusing. This commit adjusts the logic to allow master-eligible nodes to attempt an election even if they are not in the voting configuration. If such a master is successfully elected then it adds itself to the voting configuration. This commit also adjusts the logic that causes master nodes to abdicate when they are excluded from the voting configuration, to avoid the confusion described above. Relates #37712, #37802.
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Abdicates to another master-eligible node once the active master is reconfigured out of the voting configuration, for example through the use of voting configuration exclusions.
Follow-up to #37712