topic Re: Inconsistent procvar behaviour in Alfresco Archive

Inconsistent procvar behaviour

marcus1 — Mon, 19 Sep 2011 15:17:31 GMT

I found some strange behaviour regarding the storing and updating of process variables. Suppose we have the following processrocess Aervice 1 -> Task 1 -> Service 2 -> Task 2 -> Service 3Service 1 creates a new process variable:Book book = new Book("12345");execution.setVariable("boo

Re: Inconsistent procvar behaviour

trademak — Mon, 19 Sep 2011 18:48:54 GMT

Hi,

Can you attach a working test project for this problem?

Best regards,

Re: Inconsistent procvar behaviour

marcus1 — Tue, 20 Sep 2011 08:37:52 GMT

The forum doesn't seem to allow attaching files:

The extension diff is not allowed. (Same happens with other extensions)

So I made a Jira issue:

http://jira.codehaus.org/browse/ACT-934

Re: Inconsistent procvar behaviour

mathiasd — Wed, 21 Sep 2011 08:02:22 GMT

I think your problem is similar to this one : http://jira.codehaus.org/browse/ACT-820, discussed here : http://forums.activiti.org/en/viewtopic.php?f=6&t=1720 and here http://forums.activiti.org/en/viewtopic.php?f=6&t=2394

You need to re-affect the variable each time you update it :


Book book = execution.getVariable("book");
book.setTitle("Activiti in Action");
execution.setVariable("book", book);

Re: Inconsistent procvar behaviour

ronald_van_kuij — Wed, 21 Sep 2011 12:57:38 GMT

@Mathias: Good catch, I missed that…

Re: Inconsistent procvar behaviour

marcus1 — Sat, 24 Sep 2011 08:38:30 GMT

@Mathias: good to know that other people have encountered this issue. I hope we can find a solution to this

It seems to me that the cause of the problem is as follows.

Lets first look at what happens in case of Process A, which (AFAIK) works as intended.

When setVariable is called from Service1, first the list of variableInstances is initialized. Then a new VariableInstanceEntity is created. The call hierarchy is as follows:

ExecutionEntity(VariableScopeImpl).setVariable
—-ExecutionEntity(VariableScopeImpl).createVariableLocal
——–VariableInstanceEntity.createAndInsert
————VariableInstanceEntity.create
—————-VariableInstanceEntity.setValue
——————–SerializableType.setValue
————————ValueFields.setCachedValue
—————————-cachedValue = …
————————cachedValue = …

So the variable is created and added to the SqlSession, and the cachedValue is set (twice actually).

The next step in the process is a task, so the db session is flushed, causing the ExecutionEntity (and the variable) to be written to the database.

After that the next step is Service2, which calls getVariable. The call hierarchy looks like this:

ExecutionEntity(VariableScopeImpl).getVariable
—-ExecutionEntity(VariableScopeImpl).ensureVariableInstancesInitialized (not initialized yet, so fetch from db)
—-VariableInstanceEntity.getValue (cachedValue is null)
——–SerializableType.getValue (only called if cachedValue is null)
————DbSqlSession.addDeserializedObject

So ultimately getVariable causes DbSqlSession.addDeserializedObject to be called. As I understand it, this ensures that variables with updated values are flushed at the end of the transaction.

What about Process B?

The difference with Process A is the task between Service1 and Service2, so we need only look at what happens in Service2.

When Service2 calls setVariable, this is what happens:

ExecutionEntity(VariableScopeImpl).getVariable
—-ExecutionEntity(VariableScopeImpl).ensureVariableInstancesInitialized (already initialized!)
—-VariableInstanceEntity.getValue (cachedValue is already set!)
——–return cachedValue

In this case, cachedValue is not null, so SerializableType.setValue and thus DbSqlSession.addDeserializedObject is never called!

Solution

In my view, the conceptual solution is simple: addDeserializedObject needs to be called when a new variable is created, not just from getVariable.

Re: Inconsistent procvar behaviour

marcus1 — Sat, 24 Sep 2011 09:35:46 GMT

Added a patch to http://jira.codehaus.org/browse/ACT-934.