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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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Francisco Guerrero updated CASSANDRA-17226:
-------------------------------------------
                        Authors: Francisco Guerrero, Yifan Cai  (was: Francisco 
Guerrero)
    Test and Documentation Plan: Provided new unit tests to cover the new 
changes
                         Status: Patch Available  (was: In Progress)

PR available here: https://github.com/apache/cassandra/pull/1376
CI here: 
https://app.circleci.com/pipelines/github/frankgh/cassandra?branch=CASSANDRA-17226&filter=all

> 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: 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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