Re: OJB not robust against database or network failures

[John Holman]

Hi Armin

> Yes, you are right I checked in this version a few days ago. I'm not a
> DB-expert,
> so I don't now what's the best solution to get the 'validationQuery'
> from.
> 1. Use a hard-coded query from the Platform implementation class
> 2. Allow user to set the query within the jdbc-connection-descriptor
> in the repository file.
>

I'm not an expert either! But perhaps a hard coded default query from Platform which can be overridden by the user by a validationQuery attribute in jdbc-connection-descriptor or connection-pool?

In the meantime is there a way of getting hold of the PoolableConnectionFactory and setting the validation query directly in the application?

Thanks, John


Armin Waibel wrote:

Hi John,


----- Original Message -----
From: "John Holman" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, December 04, 2002 2:23 PM
Subject: OJB not robust against database or network failures

If the database or network goes down when OJB already has connections

in

the underlying pool, I've found that OJB does not recover when the
database comes back up. I think this is because after an operation

fails

the invalid connection is returned to the pool rather than being
destroyed and a new one created.

Using the built-in connection pool ConnectionFactoryConPooledImpl I
tried setting "testOnBorrow" to true in the connection-pool element of
jdbc-connection-descriptor, but this did not help. Looking at the

code,

ConnectionFactoryConPooledImpl.validateObject() just calls
java.sql.Connection.isClosed(), and this does not seem to detect that
the connection is invalid, at least for the JDBC drivers for

Postgresql

and Oracle that I'm using.

Then, I noticed that the current CVS version (0.9.8) offers a
ConnectionFactoryDBCPImpl option in OJB.properties. Using the Jakarta
DBCP connection pool directly in another application, I've found that
you can get robust behaviour by setting testOnBorrow to true and

setting

a suitable validation query (e.g. select 0 from dual for Oracle).
However, it seems that OJB sets the validation query to null. (A

comment

suggests this is because a suitable validation query would vary

between

database platforms). And there does not seem to be a configuration
option to set/override the validation query ...

Yes, you are right I checked in this version a few days ago. I'm not a
DB-expert,
so I don't now what's the best solution to get the 'validationQuery'
from.
1. Use a hard-coded query from the Platform implementation class
2. Allow user to set the query within the jdbc-connection-descriptor
in the repository file.

Any comments welcome.

regards,
Armin

I'd be grateful for any suggestions.

John.


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