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https://issues.apache.org/jira/browse/HBASE-5827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13401787#comment-13401787
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Andrew Purtell commented on HBASE-5827:
---------------------------------------
bq. We should also consider another interface based on (or at least
conceptually similar to) SU's async stuff, so you could register a callback if
you are interested in the error
@Jesse, thanks for commenting. I agree.
For illustration, what the above discussion so far considers is something like:
{noformat}
if (withCoprocessor && (coprocessorHost != null)) {
if (coprocessorHost.preGet(context, get, results)) {
return results;
}
}
+ try {
// Existing code with formatting unchanged
+ } catch (Throwable t) {
+ // failed-get CP hook
+ if (withCoprocessor && (coprocessorHost != null)) {
+ coprocessorHost.postGet(context, t, get, results);
+ }
+ rethrow t;
+ }
if (withCoprocessor && (coprocessorHost != null)) {
- coprocessorHost.postGet(context, get, results);
+ coprocessorHost.postGet(context, null, get, results);
}
{noformat}
What would the alternative look like?
> [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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