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https://issues.apache.org/jira/browse/IMPALA-12060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17715194#comment-17715194
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Wenzhe Zhou commented on IMPALA-12060:
--------------------------------------

catalogd set its subscriber-id as 
"catalog-server@<FLAG_hostname>:<FLAG_catalog_service_port>".
If two catalog instances running on different hosts are given same 
FLAG_hostname and same FLAGS_catalog_service_port, then two catalog instances 
could have same subscriber-id. For example, set FLAG_hostname as "localhost".
If FLAGS_statestore_subscriber_use_resolved_address is set as true, 
subscriber_location will be set as subscriber's resolved network address so 
that their subscriber_location are different. 
Also if FLAGS_state_store_subscriber_port are assigned to different values, 
their subscriber_location will be different.
statestore could use subscriber_location to check if the registration requests 
are came from different hosts if the two requests have same subscriber-id.

> statestore should only allow a single catalog instance to be part of cluster
> ----------------------------------------------------------------------------
>
>                 Key: IMPALA-12060
>                 URL: https://issues.apache.org/jira/browse/IMPALA-12060
>             Project: IMPALA
>          Issue Type: Bug
>            Reporter: Abhishek Rawat
>            Assignee: Wenzhe Zhou
>            Priority: Critical
>
> Today Impala doesn't support multiple catalogd instances to be part of the 
> cluster. When using external Active Passive HA mechanisms like leader 
> election, it may be possible for multiple catalog replicas to be part of the 
> cluster, in some cases. This is mainly because catalogds have no idea that 
> there are other catalogd instances. One way to address this issue could be 
> for statestore to always ensure that there could only be a single instance of 
> catalogd in the cluster. Coordinator also has a config `catalog_service_host` 
> - both statestore and coordinator should have a consistent view and consider 
> the proper catalogd instance to be part of the cluster.



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