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https://issues.apache.org/jira/browse/SOLR-6249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14097854#comment-14097854
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Timothy Potter commented on SOLR-6249:
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bq. how do we handle Schema API modifications failing on some replicas?
My thinking is that replica has to be marked down (which means it no longer
participates in update request processing or query execution). Seems
complicated to try to back-out updates on replicas where the changes were
successful, but I'm willing to explore that route too if we think it's a better
path to go down.
bq. if i'm a client and I want to update the schema and send some updates that
are dependent on the updated schema, how do I do that?
I'm adding the /schema/zkversion endpoint you suggested, so it will be
available to the client. We can also have the server-side code poll for this
across the collection (see previous comment)
> Schema API changes return success before all cores are updated
> --------------------------------------------------------------
>
> Key: SOLR-6249
> URL: https://issues.apache.org/jira/browse/SOLR-6249
> Project: Solr
> Issue Type: Improvement
> Components: Schema and Analysis, SolrCloud
> Reporter: Gregory Chanan
>
> See SOLR-6137 for more details.
> The basic issue is that Schema API changes return success when the first core
> is updated, but other cores asynchronously read the updated schema from
> ZooKeeper.
> So a client application could make a Schema API change and then index some
> documents based on the new schema that may fail on other nodes.
> Possible fixes:
> 1) Make the Schema API calls synchronous
> 2) Give the client some ability to track the state of the schema. They can
> already do this to a certain extent by checking the Schema API on all the
> replicas and verifying that the field has been added, though this is pretty
> cumbersome. Maybe it makes more sense to do this sort of thing on the
> collection level, i.e. Schema API changes return the zk version to the
> client. We add an API to return the current zk version. On a replica, if
> the zk version is >= the version the client has, the client knows that
> replica has at least seen the schema change. We could also provide an API to
> do the distribution and checking across the different replicas of the
> collection so that clients don't need ot do that themselves.
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