[jira] [Comment Edited] (HBASE-5827) [Coprocessors] Observer notifications on exceptions

["Andrew Purtell (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-5827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13401764#comment-13401764 ] 

Andrew Purtell edited comment on HBASE-5827 at 6/26/12 11:07 PM:
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I'd like to revisit the API changes under consideration here. 

Do we want a new failXXX for every operation, or should we alter the postXXX methods? 

If the latter, then do we:

provide backwards compatible postXXX methods that put the Throwable into the Context and provide a new Context method for getting the caught Throwable, or null if nothing was caught;

or pass the caught Throwable to new postXXX methods as a new parameter, still provide backwards compatible postXXX methods that put the Throwable into the Context, but also deprecate the backwards compatible postXXX methods.

Edit: To clarify a bit, with the alternatives above involving postXXX, we would move code between preXXX and postXXX hooks into a try block, and in the catch handler call postXXX. The choice presented is basically between introducing a new failXXX method for every hook point or extending postXXX semantics to cover the exception path.
                
      was (Author: apurtell):
    I'd like to revisit the API changes under consideration here. 

Do we want a new failXXX for every operation, or should we alter the postXXX methods? 

If the latter, then do we:

provide backwards compatible postXXX methods that put the Throwable into the Context and provide a new Context method for getting the caught Throwable, or null if nothing was caught;

or pass the caught Throwable to new postXXX methods as a new parameter, still provide backwards compatible postXXX methods that put the Throwable into the Context, but also deprecate the backwards compatible postXXX methods.
                  
> [Coprocessors] Observer notifications on exceptions
> ---------------------------------------------------
>
>                 Key: HBASE-5827
>                 URL: https://issues.apache.org/jira/browse/HBASE-5827
>             Project: HBase
>          Issue Type: Improvement
>          Components: coprocessors
>            Reporter: Andrew Purtell
>            Assignee: Andrew Purtell
>
> Benjamin Busjaeger wrote on dev@:
> {quote}
> Is there a reason that RegionObservers are not notified when a get/put/delete fails? Suppose I maintain some (transient) state in my Coprocessor that is created during preGet and discarded during postGet. If the get fails, postGet is not invoked, so I cannot remove the state.
> If there is a good reason, is there any other way to achieve the same thing? If not, would  it be possible to add something the snippet below to the code base?
> {code}
>     // pre-get CP hook
>     if (withCoprocessor && (coprocessorHost != null)) {
>       if (coprocessorHost.preGet(get, results)) {
>         return results;
>       }
>     }
> +    try{
>     ...
> +    } catch (Throwable t) {
> +        // failed-get CP hook
> +        if (withCoprocessor && (coprocessorHost != null)) {
> +          coprocessorHost.failedGet(get, results);
> +        }
> +        rethrow t;
> +    }
>     // post-get CP hook
>     if (withCoprocessor && (coprocessorHost != null)) {
>       coprocessorHost.postGet(get, results);
>     }
> {code}
> {quote}

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