[jira] [Updated] (KAFKA-12156) Document consequences of single threaded response handling

["Tom Bentley (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-12156?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tom Bentley updated KAFKA-12156:
--------------------------------
    Description: 
If users block the response handling thread in one call waiting for the result of a second "nested" call then the client effectively hangs because the 2nd call's response will never be processed. For example:

{noformat}
        admin.listTopics().names().thenApply(topics -> {
            // ... Some code to decide the topicsToCreate based on the topics
            admin.createTopics(topicsToCreate).all().get()
            return null;
        }).get();
{noformat}


The {{createTopics()...get()}} blocks, indefinitely preventing the {{ListTopics}} response processing from dealing with the {{CreateTopics}} response.

This can be surprising to users of the Admin API, so we should at least document that this pattern should not be used. 

  was:
If users block the response handling thread in one call waiting for the result of a second "nested" call then the client effectively hangs because the 2nd call's response will never be processed. For example:


        admin.listTopics().names().thenApply(topics -> {
            // ... Some code to decide the topicsToCreate based on the topics
            admin.createTopics(topicsToCreate).all().get()
            return null;
        }).get();


The {{createTopics()...get()}} block's indefinitely preventing the {{ListTopics}} response processing from dealing with the {{CreateTopics}} response.

This can be surprising to users of the Admin API, so we should at least document that this pattern should not be used. 


> Document consequences of single threaded response handling
> ----------------------------------------------------------
>
>                 Key: KAFKA-12156
>                 URL: https://issues.apache.org/jira/browse/KAFKA-12156
>             Project: Kafka
>          Issue Type: Improvement
>          Components: admin
>            Reporter: Tom Bentley
>            Assignee: Tom Bentley
>            Priority: Minor
>
> If users block the response handling thread in one call waiting for the result of a second "nested" call then the client effectively hangs because the 2nd call's response will never be processed. For example:
> {noformat}
>         admin.listTopics().names().thenApply(topics -> {
>             // ... Some code to decide the topicsToCreate based on the topics
>             admin.createTopics(topicsToCreate).all().get()
>             return null;
>         }).get();
> {noformat}
> The {{createTopics()...get()}} blocks, indefinitely preventing the {{ListTopics}} response processing from dealing with the {{CreateTopics}} response.
> This can be surprising to users of the Admin API, so we should at least document that this pattern should not be used. 



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