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Message-ID: <407E95E1.5020400@apache.org>
Date: Thu, 15 Apr 2004 16:02:09 +0200
From: Armin Waibel <arminw@apache.org>
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To: OJB Developers List <ojb-dev@db.apache.org>
Subject: Re: [PATCH] Replace closed connection in ConnectionManagerImpl
References: <407E91F9.4030902@gmx.at>
In-Reply-To: <407E91F9.4030902@gmx.at>
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Hi,

Lorenz Froihofer wrote:
> Hi,
> 
>  >>
>  >> It allows to replace closed connections if there is no transaction
>  >> running. Without this patch closed connections are never replaced in
>  >> ConnectionManagerImpl.
>  >>
>  >
>  >hmm, why do we need this? How can the ConnectionManager hold a closed
>  >connection? OJB classes itself never close a connection, expect in
>  >ConnectionFactory impl classes.
>  >Can you explain why you/we need this.
> 
> I use OJB with a standalone application. The ConnectionManagerImpl never 
> releases the connection.

I assume you never close the used PB instance after use. The used 
connection was "closed" (means returned to ConnectionFactory 
implementation) on PB.commitTransaction/rollbackTransaction/close. So if 
you do a read-only operation and do not close the used PB instance than 
the connection was NOT released.
If you don't want to close the used PB instance, you can use 
PB.serviceConnectionManager#releaseConnection to "close" the connection. 
But I recommend to close the PB instance after use (PB instances are 
pooled too, so this shouldn't be a performance issue).

> If I restart the MySQL database server but keep 
> the application running, the existing connection is unusable thereafter. 

This should be handled by the ConnectionFactory implementation. If you 
want do additional checks extend one of the ConnectionFactory 
implemetnations.

> The only option is to restart the application, which is not what I want.
> 
> So I thought it might be a good idea to provide a mechanism to detect 
> closed (or unusable) connections.

As said above this should be done in ConnectionFactory implementation.

regards,
Armin

> This allows to keep applications 
> running even if the database server is restartet. Sometimes database 
> connections are simply lost without even restarting the database server 
> -- yes, this happens.
> 
> Kind regards,
>   Lorenz.
> 
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