Le 05/04/2013 13:09, Konstantin Kolinko a écrit :
2013/4/5 Jean-Claude Haw-King-Chon <jchaw-king-c...@medifirst.fr>:
Hi,
I use the connection pool of tomcat7 and set a connection in a ThreadLocal.
The context is a web application : the threadLocal is configured when the
http request is initialized. The jdbc connection is closed and removed from
the threadLocal when the resquest is destroyed.
1. What exactly do you mean by "initialized" and "destroyed"?
If I'm not mistaken, each http request is treated by one thread by tomcat.
So, I have one jdbc connection for each request ( = thread).
2. No. It depends on how you use it and at what points in time you look at it.
If you look at it in a call chain, e.g. using try{ } finally block in
a Filter, then yes, all calls inside of "try" belong to the same
thread.
If you return processing to Tomcat and Tomcat makes a different call
into your code (e.g. using Async or Comet APIs), then that call can be
using a different thread from a thread pool.
(...)
My problem appears when I use Ajax. For 2 successive ajax request, I have
the error "Connection closed" : it's a random problem (the stacktrace is not
the same for the 2 attemps and it's not depending of the thread execution
order).
I know this issue :
http://tomcat.apache.org/tomcat-7.0-doc/jndi-datasource-examples-howto.html#Random_Connection_Closed_Exceptions
"These can occur when one request gets a db connection from the connection
pool and closes it twice. When using a connection pool, closing the
connection just returns it to the pool for reuse by another request, it
doesn't close the connection. And Tomcat uses multiple threads to handle
concurrent requests"
But, I'm sure, I always close the connection only once.
I use too the "validationQuery" and "testOnBorrow" parameters.
Is it possible that the connection pool returns the same connection for 2
different threads?
You can check its hash code.
So I don't understand why my connection is closed during the treatment.
Best regards,
Konstantin Kolinko
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1. What exactly do you mean by "initialized" and "destroyed"?
Sorry, to be more precise, 2 approches has been tested :
1) The connection is initialized in the servlet by a method called by
"doGet" or "doPost".
But the connection is closed (and removed from the threadLocal) by a
ServletRequestListener in the override of the "requestDestroyed" method.
2) The connection is initialized in the servlet by a method called by
"doGet" or "doPost". The process is encapsuled in a try/catch/finally block.
The connection is closed (and removed from the threadLocal) in the
finally block.
These 2 approches didn't work (random closed connection).
2. No. It depends on how you use it and at what points in time you look at it.
So for the 2 approches, I'm in a call chain.
Is it possible that the connection pool returns the same connection for 2
different threads?
You can check its hash code.
Thank you for this tip. The thread name and the connection hashCode are
now logged : I'm trying to understand the mechanism.
The first results show that the problem appears with connections
precedently closed...
My configuration :
<Resource
name="jdbc/607"
auth="Container"
type="javax.sql.DataSource"
username="xxxxx"
password="xxxxx"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/XXXXX"
removeAbandoned="true"
removeAbandonedTimeout="300"
testOnBorrow="true"
validationQuery="SELECT 1"
logAbandoned="true"
/>
Tomcat 7.0.29
Linux Fedora Core 12
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