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https://issues.apache.org/jira/browse/CASSANDRA-17226?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stefan Miklosovic updated CASSANDRA-17226:
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Reviewers: Chris Lohfink, Stefan Miklosovic (was: Chris Lohfink)
> Consistency Level Considered Connectivity Checker
> -------------------------------------------------
>
> Key: CASSANDRA-17226
> URL: https://issues.apache.org/jira/browse/CASSANDRA-17226
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Startup and Shutdown
> Reporter: Francisco Guerrero
> Assignee: Francisco Guerrero
> Priority: Normal
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> The connectivity checker runs during the startup of Cassandra, more
> specifically right after {{CassandraDaemon#setup}}. In general, it blocks for
> a certain period of time in order to establish connections with the peers in
> the cluster. The blocking is a best-effort one, meaning that the checker
> allows Cassandra to continue booting even if the criteria is not met.
> The Consistency Level Considered Connectivity Checker prioritizes the peers
> to connect, while still satisfying the desired Consistency Level. The goal of
> the new connectivity checker is to solve the read unavailable/timeout.
> The Consistency Level Considered Connectivity Checker (CL checker) uses the
> consistency level specified by the {{block_for_peers_consistency_level}}
> property to determine the number of peers to wait for in the local or remote
> datacenter before offering itself as a coordinator. Subject to the timeout
> specified by {{block_for_peers_timeout_in_secs}}.
> The supported values for the CL checker are {{ALL}}, {{QUORUM}},
> {{LOCAL_QUORUM}}, and {{EACH_QUORUM}}. The value is specified in the
> {{block_for_peers_consistency_level}} property defined in {{cassandra.yaml}}.
> The default consistency level is {{LOCAL_QUORUM}}.
> During the connectivity checker execution, peers are categorized into primary
> and secondary peers, such that primary peers are the sufficient number of
> peers required to satisfy the consistency level specified in
> {{block_for_peers_consistency_level}}. If the connection fails to any of the
> primary peers, additional connections are performed to secondary peers, and
> after the {{block_for_peers_timeout_in_secs}} timeout, validation is
> performed to make sure the CL is satisfied for all the natural replicas for
> every node.
> The CL checker does not support vnodes.
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