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Posted to users@tomcat.apache.org by Jean-Claude Haw-King-Chon <JC...@medifirst.fr> on 2013/04/05 11:37:30 UTC
Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
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.
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).
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?
So I don't understand why my connection is closed during the treatment.
Thank for your help
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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Michael-O <19...@gmx.net>.
Fist of all, do NOT top post. Use the power of your wondeful mail client.
Am 2013-04-05 13:05, schrieb Jean-Claude Haw-King-Chon:
> I wish to avoid passing the connection through the layers of the
> application (from controller to DAO).
> The controller initialize the connection and must pass it to the Dao
> layer. I don't want to pass the datasource or connection to the business
> layer as a parameter.
>
> Futher, the data source can be different for each user : it's not
> possible to use a static attribute to store the connection or the
> datasource (by example, in a connection factory).
>
> That's why I think that "threadlocal" is the solution for passing the
> connection between 2 non adjacent layers : is it a bad practice?
ThreadLocals have their use cases but must be used with great caution.
Are you certain that no one else sets the ThreadLocal and you do not
suffer from race conditions due to missing synchronization?
Michael
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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Jean-Claude Haw-King-Chon <JC...@medifirst.fr>.
I wish to avoid passing the connection through the layers of the
application (from controller to DAO).
The controller initialize the connection and must pass it to the Dao
layer. I don't want to pass the datasource or connection to the business
layer as a parameter.
Futher, the data source can be different for each user : it's not
possible to use a static attribute to store the connection or the
datasource (by example, in a connection factory).
That's why I think that "threadlocal" is the solution for passing the
connection between 2 non adjacent layers : is it a bad practice?
Jean-Claude HAW-KING-CHON
*MédiFirst **
**Immeuble LE SESAME**
*8 rue Germain Soufflot
78180 Montigny le Bretonneux
*Hotline Support: 01 79 85 39 40*
Le 05/04/2013 12:40, Michael-O a écrit :
> Am 2013-04-05 11:37, schrieb Jean-Claude Haw-King-Chon:
>> 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.
>
> Why do you do that at all?
> Why don't you simply use such an idiom in your thead/controller:
>
> ...
> Connection conn = ConnetionUtils.getReadWriteConnection(DataSource
> dataSource); // has to be implemented of course
> ..
>
> Use this connetion in the entire thread, pass it along, when you are
> done. Close it.
>
> ThreadLocals are useful in other cases but not in this one.
>
> Michael
>
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>
>
Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Michael-O <19...@gmx.net>.
Am 2013-04-05 11:37, schrieb Jean-Claude Haw-King-Chon:
> 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.
Why do you do that at all?
Why don't you simply use such an idiom in your thead/controller:
...
Connection conn = ConnetionUtils.getReadWriteConnection(DataSource
dataSource); // has to be implemented of course
..
Use this connetion in the entire thread, pass it along, when you are
done. Close it.
ThreadLocals are useful in other cases but not in this one.
Michael
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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Jose María Zaragoza <de...@gmail.com>.
Hi Konstantin:
About this link
http://commons.apache.org/proper/commons-dbcp/configuration.html
If you have enabled "removeAbandoned" then it is possible that a connection
is reclaimed by the pool because it is considered to be abandoned. This
mechanism is triggered when (getNumIdle() < 2) and (getNumActive() >
getMaxActive() - 3)
I know that it's about DBCP , not JDBC Pool in Tomcat 7, but
Do you know if it's the same mechanism ?
In this case, this mechanism only is useful when pool is about to be
exhausted, right ?
Regards
> Do you have queries that run or are used for more than 5 minutes in a
> single request?
> If so, then your removeAbandonedTimeout is too short and
> "removeAbandoned" will close them.
>
> http://commons.apache.org/proper/commons-dbcp/configuration.html
>
> BTW, your pool size is 8.
>
> Best regards,
> Konstantin Kolinko
>
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>
>
Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Konstantin Kolinko <kn...@gmail.com>.
2013/4/5 Jean-Claude Haw-King-Chon <JC...@medifirst.fr>:
> Le 05/04/2013 13:09, Konstantin Kolinko a écrit :
>>
>> 2013/4/5 Jean-Claude Haw-King-Chon <JC...@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
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
>> For additional commands, e-mail: users-help@tomcat.apache.org
>>
>>
>
> 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).
>
You should go with 2).
>
>
> 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
>
Do you have queries that run or are used for more than 5 minutes in a
single request?
If so, then your removeAbandonedTimeout is too short and
"removeAbandoned" will close them.
http://commons.apache.org/proper/commons-dbcp/configuration.html
BTW, your pool size is 8.
Best regards,
Konstantin Kolinko
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RE: Tomcat7 - ajax and connection pool : "connection closed"
despite the use of "validationQuery" and "testOnBorrow"
Posted by "Propes, Barry L " <ba...@citi.com>.
OK, thank you, Jose!
Good to know if I ever go the MySQL route.
-----Original Message-----
From: Jose María Zaragoza [mailto:demablogia@gmail.com]
Sent: Friday, April 05, 2013 5:07 PM
To: Tomcat Users List
Subject: Re: Tomcat7 - ajax and connection pool : "connection closed" despite the use of "validationQuery" and "testOnBorrow"
And that's right . You can define any SQL , but you prefer the easiest ( and fastest )
Indeed , you could use SELECT 1 FROM DUAL in MySQL, but it's not required by using FROM DUAL From MySQL doc
"DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses. MySQL may ignore the clauses. MySQL does not require FROM DUAL if no tables are referenced."
I think that Oracle requires "FROM" word in queries ( I think )
2013/4/5 Propes, Barry L <ba...@citi.com>
> Ok, thanks for clarification. I thought it had to be "from some faux
> table or object."
>
>
> -----Original Message-----
> From: Jose María Zaragoza [mailto:demablogia@gmail.com]
> Sent: Friday, April 05, 2013 3:44 PM
> To: Tomcat Users List
> Subject: Re: Tomcat7 - ajax and connection pool : "connection closed"
> despite the use of "validationQuery" and "testOnBorrow"
>
> 'select 1 from dual' works in Oracle DB
>
> In MySQL, "select 1"
>
>
> 2013/4/5 Propes, Barry L <ba...@citi.com>
>
> > I could be wrong, but is that validationQuery attribute correct?
> >
> > "SELECT 1" ? - I have validationQuery="select 1 from dual" in mine,
> > and my doc states it has to be a valid SQL statement returning at
> > least
> one row.
> >
> > That may not factor in at all, just noticed it. Looked maybe out of
> kilter.
> >
> > -----Original Message-----
> > From: Jean-Claude Haw-King-Chon
> > [mailto:JChaw-king-chon@medifirst.fr]
> > Sent: Friday, April 05, 2013 10:38 AM
> > To: Tomcat Users List
> > Subject: Re: Tomcat7 - ajax and connection pool : "connection closed"
> > despite the use of "validationQuery" and "testOnBorrow"
> >
> > ..
> >
> > 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
> >
> >
> >
> > --------------------------------------------------------------------
> > - To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> > For additional commands, e-mail: users-help@tomcat.apache.org
> >
> >
> > --------------------------------------------------------------------
> > - To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> > For additional commands, e-mail: users-help@tomcat.apache.org
> >
> >
>
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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Jose María Zaragoza <de...@gmail.com>.
And that's right . You can define any SQL , but you prefer the easiest (
and fastest )
Indeed , you could use SELECT 1 FROM DUAL in MySQL, but it's not required
by using FROM DUAL
>From MySQL doc
"DUAL is purely for the convenience of people who require that all SELECT
statements should have FROM and possibly other clauses. MySQL may ignore
the clauses. MySQL does not require FROM DUAL if no tables are referenced."
I think that Oracle requires "FROM" word in queries ( I think )
2013/4/5 Propes, Barry L <ba...@citi.com>
> Ok, thanks for clarification. I thought it had to be "from some faux table
> or object."
>
>
> -----Original Message-----
> From: Jose María Zaragoza [mailto:demablogia@gmail.com]
> Sent: Friday, April 05, 2013 3:44 PM
> To: Tomcat Users List
> Subject: Re: Tomcat7 - ajax and connection pool : "connection closed"
> despite the use of "validationQuery" and "testOnBorrow"
>
> 'select 1 from dual' works in Oracle DB
>
> In MySQL, "select 1"
>
>
> 2013/4/5 Propes, Barry L <ba...@citi.com>
>
> > I could be wrong, but is that validationQuery attribute correct?
> >
> > "SELECT 1" ? - I have validationQuery="select 1 from dual" in mine,
> > and my doc states it has to be a valid SQL statement returning at least
> one row.
> >
> > That may not factor in at all, just noticed it. Looked maybe out of
> kilter.
> >
> > -----Original Message-----
> > From: Jean-Claude Haw-King-Chon [mailto:JChaw-king-chon@medifirst.fr]
> > Sent: Friday, April 05, 2013 10:38 AM
> > To: Tomcat Users List
> > Subject: Re: Tomcat7 - ajax and connection pool : "connection closed"
> > despite the use of "validationQuery" and "testOnBorrow"
> >
> > ..
> >
> > 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
> >
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> > For additional commands, e-mail: users-help@tomcat.apache.org
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> > For additional commands, e-mail: users-help@tomcat.apache.org
> >
> >
>
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>
>
RE: Tomcat7 - ajax and connection pool : "connection closed"
despite the use of "validationQuery" and "testOnBorrow"
Posted by "Propes, Barry L " <ba...@citi.com>.
Ok, thanks for clarification. I thought it had to be "from some faux table or object."
-----Original Message-----
From: Jose María Zaragoza [mailto:demablogia@gmail.com]
Sent: Friday, April 05, 2013 3:44 PM
To: Tomcat Users List
Subject: Re: Tomcat7 - ajax and connection pool : "connection closed" despite the use of "validationQuery" and "testOnBorrow"
'select 1 from dual' works in Oracle DB
In MySQL, "select 1"
2013/4/5 Propes, Barry L <ba...@citi.com>
> I could be wrong, but is that validationQuery attribute correct?
>
> "SELECT 1" ? - I have validationQuery="select 1 from dual" in mine,
> and my doc states it has to be a valid SQL statement returning at least one row.
>
> That may not factor in at all, just noticed it. Looked maybe out of kilter.
>
> -----Original Message-----
> From: Jean-Claude Haw-King-Chon [mailto:JChaw-king-chon@medifirst.fr]
> Sent: Friday, April 05, 2013 10:38 AM
> To: Tomcat Users List
> Subject: Re: Tomcat7 - ajax and connection pool : "connection closed"
> despite the use of "validationQuery" and "testOnBorrow"
>
> ..
>
> 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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> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
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>
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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Jose María Zaragoza <de...@gmail.com>.
'select 1 from dual' works in Oracle DB
In MySQL, "select 1"
2013/4/5 Propes, Barry L <ba...@citi.com>
> I could be wrong, but is that validationQuery attribute correct?
>
> "SELECT 1" ? - I have validationQuery="select 1 from dual" in mine, and
> my doc states it has to be a valid SQL statement returning at least one row.
>
> That may not factor in at all, just noticed it. Looked maybe out of kilter.
>
> -----Original Message-----
> From: Jean-Claude Haw-King-Chon [mailto:JChaw-king-chon@medifirst.fr]
> Sent: Friday, April 05, 2013 10:38 AM
> To: Tomcat Users List
> Subject: Re: Tomcat7 - ajax and connection pool : "connection closed"
> despite the use of "validationQuery" and "testOnBorrow"
>
> ..
>
> 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
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
RE: Tomcat7 - ajax and connection pool : "connection closed"
despite the use of "validationQuery" and "testOnBorrow"
Posted by "Propes, Barry L " <ba...@citi.com>.
I could be wrong, but is that validationQuery attribute correct?
"SELECT 1" ? - I have validationQuery="select 1 from dual" in mine, and my doc states it has to be a valid SQL statement returning at least one row.
That may not factor in at all, just noticed it. Looked maybe out of kilter.
-----Original Message-----
From: Jean-Claude Haw-King-Chon [mailto:JChaw-king-chon@medifirst.fr]
Sent: Friday, April 05, 2013 10:38 AM
To: Tomcat Users List
Subject: Re: Tomcat7 - ajax and connection pool : "connection closed" despite the use of "validationQuery" and "testOnBorrow"
..
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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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Jean-Claude Haw-King-Chon <JC...@medifirst.fr>.
Le 05/04/2013 13:09, Konstantin Kolinko a écrit :
> 2013/4/5 Jean-Claude Haw-King-Chon <JC...@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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Re: Tomcat7 - ajax and connection pool : "connection closed" despite
the use of "validationQuery" and "testOnBorrow"
Posted by Konstantin Kolinko <kn...@gmail.com>.
2013/4/5 Jean-Claude Haw-King-Chon <JC...@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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