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Posted to commits@cassandra.apache.org by "Blake Eggleston (Jira)" <ji...@apache.org> on 2019/12/03 18:41:00 UTC
[jira] [Updated] (CASSANDRA-15442) Read repair implicitly increases
read timeout value
[ https://issues.apache.org/jira/browse/CASSANDRA-15442?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Blake Eggleston updated CASSANDRA-15442:
----------------------------------------
Reviewers: Blake Eggleston
> Read repair implicitly increases read timeout value
> ---------------------------------------------------
>
> Key: CASSANDRA-15442
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15442
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/Core
> Reporter: Yifan Cai
> Assignee: Yifan Cai
> Priority: Normal
>
> When read repair occurs during a read, internally, it starts several _blocking_ operations in sequence. See {{org.apache.cassandra.service.StorageProxy#fetchRows}}.
> The timeline of the blocking operations
> # Regular read, wait for full data/digest read response to complete. {{reads[*].awaitResponses();}}
> # Read repair read, wait for full data read response to complete. {{reads[*].awaitReadRepair();}}
> # Read repair write, wait for write response to complete. {{concatAndBlockOnRepair(results, repairs);}}
> Step 1 and 2 each waits for the duration of read timeout, say 5 s.
> Step 3 waits for the duration of write timeout, say 2 s.
> In the worse case, the actual time taken for a read could accumulate to ~12 s, if each individual step does not exceed the timeout value.
> From the client perspective, it does not expect a request taken way higher than the database configured timeout value.
> Such scenario is especially bad for the clients that have set up client-side timeout monitoring close to the configured one. The clients think the operations timed out and abort, but they are in fact still running on server.
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