[Registry-dev] Transaction support in the embedded registry

[Deepal Jayasinghe]

Hi Chathura ,
>
> I am implementing the transaction support in the embedded registry 
> layer. I have introduced below four methods to the Registry API to 
> handle transactions. These methods can be used by client application 
> in a similar way to JDBC connection transactions.
>
> registry.beginTransaction();
>
> registry.commit();
>
> registry.rollback();
>
> registry.endTransaction();
Rather than adding these methods to registry API cant we come up with a 
new class (say TransactionManager) and add those four methods there. And 
we can create the TransactionManager by giving the registry instance or 
whatever needed.
>
> When beginTransaction() is called, a database connection is obtained 
> and stored in a thread local variable. Then all other database related 
> registry components use that connection by calling:
Well this a problem when it comes to APP, because in the case of APP 
storing in the thread local will not provide what we want. Because when 
we use APP for each and every request it creates a new thread so what we 
store in last request can not access from the new request.

I think we need to think this in bit higher level , something like RM 
session. Where when a user start a transaction we give him  a session 
key (and store the connection in a table alone with the key) and he is 
supposed to send the key back when he call the second call in the same 
transaction. If we do so we can handle this in APP without having any 
problem.
>
> Connection conn = Transaction.getConnection();
>
> When a transaction is started, connections are not commited unless 
> registry.commit() is called. Therefore, client application can perform 
> sequence of operations in a single transaction by listing them within 
> registry.beginTransaction() and registry.commit(). Once the 
> transaction is complete client applications should call 
> registry.endTransaction(), so that the connection is closed and the 
> thread local variable is cleared.
What happen if the client does not call endTransaction ?

Someone can attack registry by just creating transactions and not 
closing them , I think we have to agree what we are going to do on this.

Thank you!
Deepal