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Posted to issues-all@impala.apache.org by "Sahil Takiar (Jira)" <ji...@apache.org> on 2019/09/20 19:38:00 UTC
[jira] [Commented] (IMPALA-8962) FETCH_ROWS_TIMEOUT_MS should apply
before rows are available
[ https://issues.apache.org/jira/browse/IMPALA-8962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16934703#comment-16934703 ]
Sahil Takiar commented on IMPALA-8962:
--------------------------------------
Not sure of the best way to do this, some notes:
* Not sure if it is safe to remove the {{BlockOnWait}} call entirely and just let the {{PlanRootSink}} block
* Modify {{BlockOnWait}} to take a timeout, and use the same value as {{FETCH_ROWS_TIMEOUT_MS}}
* Same as above, but use a dedicated config like {{FETCH_WAIT_FINISHED_TIMEOUT_MS}} (the amount of time fetch requests wait for the query to transition to the 'FINISHED' state before returning)
> FETCH_ROWS_TIMEOUT_MS should apply before rows are available
> ------------------------------------------------------------
>
> Key: IMPALA-8962
> URL: https://issues.apache.org/jira/browse/IMPALA-8962
> Project: IMPALA
> Issue Type: Bug
> Components: Clients
> Reporter: Sahil Takiar
> Assignee: Sahil Takiar
> Priority: Major
>
> IMPALA-7312 added a fetch timeout controlled by the query option {{FETCH_ROWS_TIMEOUT_MS}}. The issue is that the timeout only applies after the *first* batch of rows are available. The issue is that both Beeswax and HS2 clients call {{request_state->BlockOnWait}} inside {{ImpalaServer::FetchInternal}}. The call to {{BlockOnWait}} blocks until rows are ready to be consumed via {{ClientRequestState::FetchRows}}.
> So clients can still end up blocking indefinitely waiting for the first row batch to appear.
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