Re: Memory leak with c3p0 using ConnectionProperties

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Achim Abeling wrote:
> Hi,
> 
> I think I found a memory leak in mysql-connector-3.1.11.
> 
> Perhaps the cause for the memory leak is in c3p0, but since the memory
> leak goes away when the JDBC url is changed I first post the problem here.
> 
> A class to reproduce the problem is attached.
> I am using mysql-connector-3.1.11 and c3p0 version 0.9.0 with JDK 1.5.0.
> 
> c3p0 has the possibility to expire idling connections. The test case
> sets an expire time of 1 second.
> The log shows that c3p0 really expires the connections and creates new
> connections.
> 
> When the JDBC url is
> "jdbc:mysql://localhost/test?profileSQL=true"
> the memory leak occurs, when it is
> "jdbc:mysql://localhost/test"
> it occurs not.
> 
> The memory leak can be observed by starting the class and then doing a
> # jmap -histo <processid> |grep "com.mysql.jdbc.Connection"
> 
> On my linux workstation it produces something like this:
> 
> Attaching to process ID 14539, please wait...
> Debugger attached successfully.
> Client compiler detected.
> JVM version is 1.5.0-b64
> Iterating over heap. This may take a while...
> 1180872 16401 com.mysql.jdbc.ConnectionProperties$BooleanConnectionProperty
> 277200  3465 com.mysql.jdbc.ConnectionProperties$IntegerConnectionProperty
> 182952  2541   
> com.mysql.jdbc.ConnectionProperties$StringConnectionProperty
> 168168  231     com.mysql.jdbc.Connection
> 36960   462
> com.mysql.jdbc.ConnectionProperties$MemorySizeConnectionProperty
> Heap traversal took 9.15 seconds.
> 
> The second number in each line is the object count. And it is increasing.
> 
> Greetings
> Achim

Achim,

Adding "profileSQL=true" to your URL causes the driver to log _every_
query to System.err, or another defined logger, so depending on how your
logging is setup, that could be filling a lot of memory due to how your
logging system buffers things.

"profileSQL" is not designed to be used in a production setting, is
there a reason you're running it in this manner?

	-Mark
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