topic Re: ByteArrayEntity: improve encapsulation in Alfresco Archive

ByteArrayEntity: improve encapsulation

marcus1 — Mon, 13 May 2013 15:00:50 GMT

I've run into a nasty bug in a custom variable type causing Foreign Key Constaint error in ACT_FK_VAR_BYTEARRAY.The first part of solving the problem was to improve logging in DbSqlSession. This helped me diagnose what went wrong. These changes you can find in this pull request:https://github.com/Ac

Re: ByteArrayEntity: improve encapsulation

rrludwig — Wed, 22 May 2013 11:59:38 GMT

This issue causes some more trouble. Due to updates of these byte array ids, we run into race conditions. During an update of a value we find time slots where we get an id which is not valid anymore. These leads to NullPointerExceptions… 😞 But, we do not have a custom implementation, we just use the normal Activiti API and call getVariables() to HistoryService and RuntimeService quite frequently.

The issue is also responsible for the ticket I created: http://jira.codehaus.org/browse/ACT-1687

The handling of byte arrays and serializables need to be changed, in my opinion. The method setByteArrayValue mentioned above should be changed in the following way:

1) Check for existence of a former value. If there is one, perform an update in the database if the value to be set is not null.
2) If a former value exists, but the new value is null, perform a delete.
3) If no value exists and the new value is not null, perform an insert.
4) No former value and new value is null, do nothing.

Maybe, even a null value should be put into ACT_GE_BYTEARRAY table. So each serializable variable get a single, constant id.

Re: ByteArrayEntity: improve encapsulation

jbarrez — Thu, 23 May 2013 15:53:05 GMT

@Marcus: I agree with what you are writing. If you create a pull request, we can continue the discussion there.

@rrludwig: thanks for reporting the issue. We will look into it.

But it sounds strange that this race condition occurs. Shouldn't transaction prevent this problem?

Re: ByteArrayEntity: improve encapsulation

marcus1 — Sat, 25 May 2013 08:40:20 GMT

Re: ByteArrayEntity: improve encapsulation

marcus1 — Mon, 27 May 2013 08:19:22 GMT

You can follow my progresss here if you want:

https://github.com/marcusk24/Activiti/commits/master

There are quite a number of changes, but I've tried to group the commits into understandable bite-size chunks.

It is already funtional. However, I still want to clean up the duplicate code in the classes that deal with ByteArrayEntities. I'll probably get to this tomorrow.

Re: ByteArrayEntity: improve encapsulation

marcus1 — Sun, 09 Jun 2013 09:28:03 GMT

Done: https://github.com/Activiti/Activiti/pull/83

Re: ByteArrayEntity: improve encapsulation

frederikherema1 — Mon, 10 Jun 2013 15:01:17 GMT

Thanks for your contribution, we're looking into it to get it reviewed.