Feature suggestion/request: BatchCaller cancel

[nva]

I think the following could be quite handy:

Use case:

1. Large/expensive RPCs are grouped into a single round-trip with the BatchCaller.

2. User input triggers the BatchCaller in 1.

3. A second user input is received before the batch completes that makes the processing started in 1. obsolete.

To save resources, it would be very handy if in step 3. a cancel could be called on the batch to stop all callbacks that haven't been called yet. Of course, with the understanding that the application state would be unpredictable as there would be no way knowing which callback has run and which has not.

Typical scenario: tabbed application, each tab requires data from the server to render. User switches to another tab before the loading/initialisation of the tab finishes. Blocking the user input during loading not feasible.

What do you think?

Cheers,

V.

[csa]

Hi Valentin,

Yes, that sounds like a good idea! Can you create a JIRA for it?

If that's something you want to implement yourself and send a pull request it will be much appreciated!

Cheers,

Christian

[nva]

Hi Christian,

sounds good thanks. Will take a stab at implementing it. Is this the right JIRA: https://github.com/errai/errai/issues

Cheers,

V.

[csa]

Hi,

great! Here's the link to our JIRA: https://issues.jboss.org/browse/ERRAI

Christian

[nva]

Thanks! Created https://issues.jboss.org/browse/ERRAI-630.

The patch is in testing, will send the git pull request when I figure out how to do it (I am a cvs and svn man ).

[csa]

Excellent! If you add a unit test or enhance an existing one, you can send the PR to the 2.4 branch. Then it will be in the next release.

[nva]

I've added a test to BatchCallerIntegrationTest. It's somewhat of a naive one: am calling a service that has a built-in delay so that the cancel is issued before there can be a response. Then I assert that my callbacks have not been called.

Am struggling a bit running the unit test:

mvn -Dorg.jboss.errai.ioc.support.bus.tests.client.BatchCallerIntegrationTest -DskipTests=false clean test

And tests are still skipped. Is there a trick?

I did some end-to-end testing in my project and the cancel seems to behave as expected. However, the unit test must work.

[csa]

Ah yes, you will need to activate the integration-test profile: mvn -Pintegration-test clean test

[nva]

Thanks. Just realised as I wrote the previous comment, the unit test doesn't cover the use case properly. The callbacks will not have been called, regardless whether the was a cancel or not: the RPC is not finished at that point. Need to think about it a bit more.

[nva]

Ok, I have a really good-looking unit test now and it shows that the task is not as trivial as I thought. The power of unit tests. Will make future comments/ask questions on the JIRA ticket.