Transaction Management

[YK 7 <yk...@gmail.com>]

Hi,

I'm new to Cayenne and I'm testing the Cayenne's transaction management
using the following scenario:

I have a simple web application that uses Spring to create
singletons(Services, DAOs...) and make the dependencies injection.
My example is using two different Databases (MySQL and Oracle) and thus, I
have defined two Cayenne Server Runtimes:
One for Oracle and one for MySQL. Those two ServerRuntimes are instantiated
once in a singleton.

The ObjectContexts are instantiated once per HTTP session and sent to the
DAOs via ThreadLocal (This is very similar to the Cayenne's HTTP filter).
Everything works well if I use directly objectContext.commitChanges()
method to commit changes to DB.

What I'm trying to do next is to use Cayenne Transactions using :
Transaction tx = serverRuntime.getDataDomain().createTransaction().
....
tx.commit(); //or tx.rollback() depending on the situation

The problem here is that if I do so, it means that if a user(or HTTP
session) changes are committed, all other users(or HTTP sessions) changes
will also be committed.
This is because serverRuntime is a singleton and the transaction is created
against it (and not against the objectContext which is bound to the HTTP
session).

I also took a look at the ServerRuntime source code and noticed that it
defines two instance properties (injector and modules which are in the
parent class: CayenneRuntime).

If I'm not mistaken, this means that ServerRuntime is not a good candidate
to be defined as a singleton (one instance per application).

Maybe I'm not correctly using Cayenne to manage transaction when we have
more than one server runtime. If so, what's the best way to achieve that
please?


Thanks

Re: Transaction Management

[YK 7 <yk...@gmail.com>]

1. I already tested object context commitChanges method without any problem.

2. I'm using two DIFFERENT databases: Oracle and MySQL.
Actually, I'm using a schema for Oracle and a catalog for MySQL.
Please, note that there entities of the tow DBs are completely independent.


On Sat, Mar 17, 2012 at 2:54 PM, John Huss <jo...@gmail.com> wrote:

> ServerRuntime should be a singleton, that is correct.
>
> ObjectContexts are dependent of each other (unless explicitly nested) so
> committing one will one commit the changes in THAT context, not the changes
> for other users if you are creating separate contexts for each user.
>
> This is because Cayenne does not start a transaction or issue any INSERT,
> UPDATE, DELETE SQL statements until you call commitChanges. All
> modifications are performed in memory only until you commit.  When you
> commit an ObjectContext, it generates the SQL statements only for the
> modifications it contains and executes them in a transaction.  So the
> contexts are independent.
>
> Are your two databases using the same schema or different (complementary)
> schema?
>
> On Sat, Mar 17, 2012 at 3:16 AM, YK 7 <yk...@gmail.com> wrote:
>
> > Hi,
> >
> > I'm new to Cayenne and I'm testing the Cayenne's transaction management
> > using the following scenario:
> >
> > I have a simple web application that uses Spring to create
> > singletons(Services, DAOs...) and make the dependencies injection.
> > My example is using two different Databases (MySQL and Oracle) and thus,
> I
> > have defined two Cayenne Server Runtimes:
> > One for Oracle and one for MySQL. Those two ServerRuntimes are
> instantiated
> > once in a singleton.
> >
> > The ObjectContexts are instantiated once per HTTP session and sent to the
> > DAOs via ThreadLocal (This is very similar to the Cayenne's HTTP filter).
> > Everything works well if I use directly objectContext.commitChanges()
> > method to commit changes to DB.
> >
> > What I'm trying to do next is to use Cayenne Transactions using :
> > Transaction tx = serverRuntime.getDataDomain().createTransaction().
> > ....
> > tx.commit(); //or tx.rollback() depending on the situation
> >
> > The problem here is that if I do so, it means that if a user(or HTTP
> > session) changes are committed, all other users(or HTTP sessions) changes
> > will also be committed.
> > This is because serverRuntime is a singleton and the transaction is
> created
> > against it (and not against the objectContext which is bound to the HTTP
> > session).
> >
> > I also took a look at the ServerRuntime source code and noticed that it
> > defines two instance properties (injector and modules which are in the
> > parent class: CayenneRuntime).
> >
> > If I'm not mistaken, this means that ServerRuntime is not a good
> candidate
> > to be defined as a singleton (one instance per application).
> >
> > Maybe I'm not correctly using Cayenne to manage transaction when we have
> > more than one server runtime. If so, what's the best way to achieve that
> > please?
> >
> >
> > Thanks
> >
>

Re: Transaction Management

[John Huss <jo...@gmail.com>]

ServerRuntime should be a singleton, that is correct.

ObjectContexts are dependent of each other (unless explicitly nested) so
committing one will one commit the changes in THAT context, not the changes
for other users if you are creating separate contexts for each user.

This is because Cayenne does not start a transaction or issue any INSERT,
UPDATE, DELETE SQL statements until you call commitChanges. All
modifications are performed in memory only until you commit.  When you
commit an ObjectContext, it generates the SQL statements only for the
modifications it contains and executes them in a transaction.  So the
contexts are independent.

Are your two databases using the same schema or different (complementary)
schema?

On Sat, Mar 17, 2012 at 3:16 AM, YK 7 <yk...@gmail.com> wrote:

> Hi,
>
> I'm new to Cayenne and I'm testing the Cayenne's transaction management
> using the following scenario:
>
> I have a simple web application that uses Spring to create
> singletons(Services, DAOs...) and make the dependencies injection.
> My example is using two different Databases (MySQL and Oracle) and thus, I
> have defined two Cayenne Server Runtimes:
> One for Oracle and one for MySQL. Those two ServerRuntimes are instantiated
> once in a singleton.
>
> The ObjectContexts are instantiated once per HTTP session and sent to the
> DAOs via ThreadLocal (This is very similar to the Cayenne's HTTP filter).
> Everything works well if I use directly objectContext.commitChanges()
> method to commit changes to DB.
>
> What I'm trying to do next is to use Cayenne Transactions using :
> Transaction tx = serverRuntime.getDataDomain().createTransaction().
> ....
> tx.commit(); //or tx.rollback() depending on the situation
>
> The problem here is that if I do so, it means that if a user(or HTTP
> session) changes are committed, all other users(or HTTP sessions) changes
> will also be committed.
> This is because serverRuntime is a singleton and the transaction is created
> against it (and not against the objectContext which is bound to the HTTP
> session).
>
> I also took a look at the ServerRuntime source code and noticed that it
> defines two instance properties (injector and modules which are in the
> parent class: CayenneRuntime).
>
> If I'm not mistaken, this means that ServerRuntime is not a good candidate
> to be defined as a singleton (one instance per application).
>
> Maybe I'm not correctly using Cayenne to manage transaction when we have
> more than one server runtime. If so, what's the best way to achieve that
> please?
>
>
> Thanks
>