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From "Richard Eckart de Castilho (JIRA)" <...@uima.apache.org>
Subject [jira] [Commented] (UIMA-5763) UIMA: need a way to lock a CAS to prevent user from releasing it prematurely
Date Thu, 19 Apr 2018 17:30:00 GMT

    [ https://issues.apache.org/jira/browse/UIMA-5763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16444426#comment-16444426

Richard Eckart de Castilho commented on UIMA-5763:

I would welcome a flag that marks a CAS as read-only. We have recently implemented write-protection
layer around the CAS based on Java dynamic proxies - but a flag within the CAS proper would
be a much better solution.

Use-case: an annotation tool where the CAS is updated by a user action, then saved, and then
forwarded to other parts of the application for post-update actions. We want to avoid that
the post-update actions make modifications to the CAS. Any such modifications would likely
be bugs because after the CAS has been updated and saved once, further updates would not be

> UIMA: need a way to lock a CAS to prevent user from releasing it prematurely
> ----------------------------------------------------------------------------
>                 Key: UIMA-5763
>                 URL: https://issues.apache.org/jira/browse/UIMA-5763
>             Project: UIMA
>          Issue Type: New Feature
>          Components: UIMA
>            Reporter: Jerry Cwiklik
>            Assignee: Marshall Schor
>            Priority: Major
>             Fix For: 3.0.1SDK, 2.10.3SDK
> UIMA-AS client supports an async style of sending CASes for processing to a remote service.
When using sendCAS( CAS aCas), the code serializes CAS and dispatches it to the remote but
keeps the CAS in a cache. When a reply comes, the cached CAS is used to deserialize a response.
The contract is that the user code should not call CAS.release(). When a reply finally comes,
the CAS is handed over to an application callback and upon return from the callback, the UIMA-AS
releases the CAS. 
> Problem: there is nothing to prevent user code to violate the contract. If CAS.release()
is called while UIMA-AS client awaits reply (or during reply deserialization), bad things
happen. In a specific use case, a NPE was thrown during deserialization and debugging was
quite painful.
> Proposed solution: to protect integrity of a CAS need a way to lock/unlock it. Such facility
can be added to CASImpl class. When a user code tries to call release()  when a CAS is locked, 
the code should throw an exception (IllegalStateException or similar). 

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