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Posted to issues-all@impala.apache.org by "Sahil Takiar (Jira)" <ji...@apache.org> on 2020/05/08 14:30:00 UTC
[jira] [Commented] (IMPALA-9124) Transparently retry queries that
fail due to cluster membership changes
[ https://issues.apache.org/jira/browse/IMPALA-9124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17102628#comment-17102628 ]
Sahil Takiar commented on IMPALA-9124:
--------------------------------------
Disclaimer: while this feature is referred to as *transparent* query retries, clients may see some unexpected behavior when a query is retried. The retry will not be 100% transparent to the end client, there will be some differences that requires client-awareness of query retries:
* When a query is retried, the retry is modeled as a brand new query with a new query id - which will be distinct from the query id of the originally submitted query that ultimately failed
* Since a query retry is a brand new query, that query has its own runtime profile as well - the runtime profiles of the failed and retried queries will be linked together
* When requesting a runtime profile from the ImpalaService, the GetRuntimeProfile() method will always return the profile of the latest query attempt - there are plans to add new options to the ImpalaService interface so that users can fetch the profiles of failed attempts as well; this does not apply for the web ui - users can still get all query profiles (for both failed and retried queries) from the web ui
> Transparently retry queries that fail due to cluster membership changes
> -----------------------------------------------------------------------
>
> Key: IMPALA-9124
> URL: https://issues.apache.org/jira/browse/IMPALA-9124
> Project: IMPALA
> Issue Type: New Feature
> Components: Backend, Clients
> Reporter: Sahil Takiar
> Assignee: Sahil Takiar
> Priority: Critical
> Attachments: Impala Transparent Query Retries.pdf
>
>
> Currently, if the Impala Coordinator or any Executors run into errors during query execution, Impala will fail the entire query. It would improve user experience to transparently retry the query for some transient, recoverable errors.
> This JIRA focuses on retrying queries that would otherwise fail due to cluster membership changes. Specifically, node failures that cause changes in the cluster membership (currently the Coordinator cancels all queries running on a node if it detects that the node is no longer part of the cluster) and node blacklisting (the Coordinator blacklists a node because it detects a problem with that node - can’t execute RPCs against the node). It is not focused on retrying general errors (e.g. any frontend errors, MemLimitExceeded exceptions, etc.).
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