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https://issues.apache.org/jira/browse/SOLR-9226?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18132143#comment-18132143
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Nick Shanin commented on SOLR-9226:
-----------------------------------
>From code reading against apache/main b73f03976fa, FORCELEADER is only
>dispatched from the manual collections action
>(solr/core/src/java/org/apache/solr/handler/admin/CollectionsHandler.java:703-706;
> solr/core/src/java/org/apache/solr/handler/admin/api/ForceLeader.java:50).
>The open choice is whether Solr should add an opt-in config setting that runs
>FORCELEADER automatically when a shard has no leader. Option one adds that
>setting, off by default, so high-availability users can enable automatic
>leader forcing, with the silent data loss risk noted in the ticket comments.
>Option two keeps FORCELEADER manual, so an operator decides each time a shard
>is forced to elect a leader. Which of these two options do you prefer?
🤖 AI-generated 🤖
> Automatically fire FORCELEADER if shard leader is missing
> ---------------------------------------------------------
>
> Key: SOLR-9226
> URL: https://issues.apache.org/jira/browse/SOLR-9226
> Project: Solr
> Issue Type: Bug
> Reporter: Noble Paul
> Assignee: Noble Paul
> Priority: Major
>
> We have seen the shards losing leader often.
> {code}
> x:lamp_2016050713_shard2_replica1] o.a.s.c.ZkController Error getting leader
> from zk
> org.apache.solr.common.SolrException: Could not get leader props
> at
> org.apache.solr.cloud.ZkController.getLeaderProps(ZkController.java:1044)
> at
> org.apache.solr.cloud.ZkController.getLeaderProps(ZkController.java:1011)
> at org.apache.solr.cloud.ZkController.getLeader(ZkController.java:967)
> at org.apache.solr.cloud.ZkController.register(ZkController.java:906)
> at org.apache.solr.cloud.ZkController.register(ZkController.java:849)
> at org.apache.solr.core.ZkContainer$2.run(ZkContainer.java:183)
> {code}
> There could be other instances as well
> I recommend the following to heal such clusters
> * Whenever a node finds that the shard has no LEADER, it should fire the
> force FORCELEADER command
> * FORCELEADER command is executed in the node that receives the command. It
> should be moved to overseer to ensure that we don't run multiple such
> commands in parallel.
> * The command should make the best effort to identify a leader and should
> assign a leader if at least one node is live in the shard
> * When a shard has lost the leader, it is very likely that thousands of such
> requests will be fired and they would clog the work queue. This command
> should ensure that duplicate requests for FORCELEADER are consumed up from
> the work-queue
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