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https://issues.apache.org/jira/browse/CASSANDRA-17071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17445749#comment-17445749
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Jacek Lewandowski edited comment on CASSANDRA-17071 at 11/24/21, 9:20 AM:
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||PR||j11||
|[trunk|https://github.com/apache/cassandra/pull/1331]|[(/)|https://app.circleci.com/pipelines/github/jacek-lewandowski/cassandra/141/workflows/d2416e08-1e4c-44df-a411-53a4fd4ef4ea]
was (Author: jlewandowski):
||PR||
|[trunk|https://github.com/apache/cassandra/pull/1331]|
> Relax schema synchronization when opening a keyspace
> ----------------------------------------------------
>
> Key: CASSANDRA-17071
> URL: https://issues.apache.org/jira/browse/CASSANDRA-17071
> Project: Cassandra
> Issue Type: Improvement
> Components: Cluster/Schema
> Reporter: Jacek Lewandowski
> Assignee: Jacek Lewandowski
> Priority: Normal
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> Extracted this as a separate ticket per discussion on CASSANDRA-17044
> In short, there are two purposes of this change:
> # Move the code around to the more appropriate places (for example, CFS
> specific code for dropping table was moved from SM class to CFS class)
> # Relax the synchronization when adding/removing keyspace instances in SM -
> instead of synchronizing the whole collection of keyspace instances, we only
> synchronize the related item (the original idea authored by [~blambov]).
> The current implementation works because a certain order of opening keyspaces
> is assumed. If a keyspace is already initialized, it is just returned without
> sync and sync is done only to initialize the keyspace. When synchronization
> is extended to the whole method, the system finds itself in a deadlock. This
> means that some keyspace is tried to be opened during initiazation. Currently
> it works fine because the keyspace which is not initialized yet is never
> tried to be opened asynchronously while initializing some other keyspace in a
> different thread. Hence the conclusion about fragility of the current
> solution.
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