Connection pooling in multithreaded app results in occasional "Closed Statement" exc"

Hi there,
I'm writing a CORBA servant, which amongst all calls in a stored procedure. I'm using connection pooling (just by example) from multiple threads and use grabbed connection to prepare an SP statement, execute it, and close both statement and connection (to return it to the pool). My stress tests run fine for the most part but once in a while throws out "Closed Statement" exception when trying to excecute the prepared statement.
The reference platform is Solaris7, thin driver 8.1.6 for Java2, jdk 1.2.2, Oracle 8.1.5 (backend), ORBacus 3.3 (external application orb).
Do you guys have any "multithreaded" statements as far as pooling concerned? Let me know if you need code, schema, anything at all. Any recommendations are greatly appreciated too, like "don't use prepared statements, don't use pooling from multiple threads, download upgrade, etc". Thanks ahead.
Yours,
-Evgeni

Dear Oracle JDBC Development Team,
First of all, I object to your comment "Please don't spread wrong information.". I do not spread wrong information. That is why I wrote in my previous email, "it isn't thread safe (as far as my tests have shown)". My statement is thus conditional on MY testing. I recognise the fact that I could be wrong. Hence, the conditional clause.
As for the claim that OracleConnectionCacheImpl is thread safe - well, since it is your software then all I can do is believe you. However, I repeatedly get a java.util.EmptyStackException from calls to oracle.jdbc.pool.OracleConnectionCacheImpl.getConnection() when running my test WITHOUT using the "synchronized" clause on the OracleConnectionCacheImpl object.
This, of course, could be due to the fact that my test is faulty. I don't know. I can't see the fault in any case. If you can help me with this then I would be more than grateful.
In any case, when I use the "synchronized" statement on OracleConnectionCacheImpl then this error disappears in a multithreaded environment.
Another interesting thing my test showed was that the JDBC driver seems to hang under heavy workload. Again, I could be WRONG. It could be my test that causes the problem, however, it is very hard to pinpoint the problem.
I would really appreciate help with this, if you have time, as we are using OracleConnectionCacheImpl in a major Internet billing system. If you wish to help then please send me an email to [email protected] (or [email protected]) and I will then send you my source code for the test.
In any case, I will word my messages with even more care in future!
regards,
Alexander Day
null

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Setting up Connection Pool in sun app server 8.1 with SQL server 2000

Hello,
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Connection pooling and auditing on an oracle database

Integration of a weblogic application with an oracle backend,
Connection pooling, and auditing ,2 conflicting requirements ?
Problem statement :
We are in the process of maintaining a legacy client server application where
the client is
written in PowerBuilder and the backend is using an Oracle database.
Almost all business logic is implemented in stored procedures on the database.
When working in client/server mode ,1 PowerBuilder User has a one-to-one relation
with
a connection(session) on the oracle database.
It is a requirement that the database administrator must see the real user connected
to the database
and NOT some kind of superuser, therefore in the PowerBuilder app each user connects
to the database
with his own username.(Each user is configured on the database via a seperate
powerbuilder security app).
For the PowerBuilder app all is fine and this app can maintain conversional state(setting
and
reading of global variables in oracle packages).
The management is pushing for web-based application where we will be using bea
weblogic appserver(J2EE based).
We have build an business app which is web-based and accessing the same oracle
backend app as
the PowerBuilder app is doing.
The first version of this web-based app is using a custom build connector(based
on JCA standard and
derived from a template provided by the weblogic integration installation).
This custom build connector is essentially a combination of a custom realm in
weblogic terms
and a degraded connection pool , where each web session(browser) has a one-to-one
relation
with the back end database.
The reason that this custom connector is combining the security functionality
and the pooling
functionality , is because each user must be authenticated against the oracle
database(security requirement)
and NOT against a LDAP server, and we are using a statefull backend(oracle packages)
which would make it
difficult to reuse connections.
A problem that surfaced while doing heavy loadtesting with the custom connector,
is that sometimes connections are closed and new ones made in the midst of a transaction.
If you imagine a scenario where a session bean creates a business entity ,and
the session bean
calls 1 entity bean for the header and 1 entity bean for the detail, then the
header and detail
must be created in the same transaction AND with the same connection(there is
a parent-child relationship
between header and detail enforced on the back end database via Primary and Foreing
Keys).
We have not yet found why weblogic is closing the connection!
A second problem that we are experincing with the custom connector, is the use
of CMP(container managed persistence)
within entity beans.
The J2EE developers state that the use of CMP decreases the develoment time and
thus also maintenance costs.
We have not yet found a way to integrate a custom connector with the CMP persistence
scheme !
In order to solve our loadtesting and CMP persistence problems i was asked to
come up with a solution
which should not use a custom connector,but use standard connection pools from
weblogic.
To resolve the authentication problem on weblogic i could make a custom realm
which connects to the
backend database with the username and password, and if the connection is ok ,
i could consider this
user as authenticated in weblogic.
That still leaves me with the problem of auditing and pooling.
If i were to use a standard connection pool,then all transaction made in the oracle
database
would be done by a pool user or super user, a solution which will be rejected
by our local security officer,
because you can not see which real user made a transaction in the database.
I could still use the connection pool and in the application , advise the application
developers
to set an oracle package variable with the real user, then on arrival of the request
in the database,
the logic could use this package variable to set the transaction user.
There are still problems with this approach :
- The administrator of the database can still not see who is connected , he will
only see the superuser connection.
- This scheme can not be used when you want to use CMP persistence , since it
is weblogic who will generate the code
to access the database.
I thought i had a solution when oracle provided us with a connection pool known
as OracleOCIConnectionPool
where there is a connection made by a superuser, but where sessions are multiplexed
over this physical pipe with the real user.
I can not seem to properly integrate this OCI connectionpool into weblogic.
When using this pool , and we are coming into a bean (session or entity bean)
weblogic is wrapping
this pool with it's own internal Datasource and giving me back a connection of
the superuser, but not one for the real user,
thus setting me with my back to the wall again.
I would appreciate if anyone had experienced the same problem to share a possible
solution with us
in order to satisfy all requirements(security,auditing,CMP).
Many Thanks
Blyau Gino
[email protected]

Hi Blyau,
As Joe has already provided some technical advice,
I'll try to say something on engineering process level.
While migrating an application from one technology to
other, like client-server to n-tier in you case, customers and
stakeholders want to push into the new system as many old
requirements as possible. This approach is AKA "we must
have ALL of the features of the old system". Mostly it happens
because they don't know what they want. Ad little understanding
of abilities of the new technology, and you will get a requirement
like the one you have in you hands.
I think "DBA must see real user" is one of those. For this
type of requirements it can make sense to try to drop it,
or to understand its nature and suggest alternatives. In this
particular case it can be a system that logs user names,
login and logout times.
Blind copying of old features into an incompatible new architecture
may endanger the whole project and can result in its failure.
Hope this helps.
Regards,
Slava Imeshev
"Blyau Gino" <[email protected]> wrote in message
news:[email protected]...
>
Integration of a weblogic application with an oracle backend,
Connection pooling, and auditing ,2 conflicting requirements ?
Problem statement :
We are in the process of maintaining a legacy client server applicationwhere
the client is
written in PowerBuilder and the backend is using an Oracle database.
Almost all business logic is implemented in stored procedures on thedatabase.
When working in client/server mode ,1 PowerBuilder User has a one-to-onerelation
with
a connection(session) on the oracle database.
It is a requirement that the database administrator must see the real userconnected
to the database
and NOT some kind of superuser, therefore in the PowerBuilder app eachuser connects
to the database
with his own username.(Each user is configured on the database via aseperate
powerbuilder security app).
For the PowerBuilder app all is fine and this app can maintainconversional state(setting
and
reading of global variables in oracle packages).
The management is pushing for web-based application where we will be usingbea
weblogic appserver(J2EE based).
We have build an business app which is web-based and accessing the sameoracle
backend app as
the PowerBuilder app is doing.
The first version of this web-based app is using a custom buildconnector(based
on JCA standard and
derived from a template provided by the weblogic integrationinstallation).
This custom build connector is essentially a combination of a custom realmin
weblogic terms
and a degraded connection pool , where each web session(browser) has aone-to-one
relation
with the back end database.
The reason that this custom connector is combining the securityfunctionality
and the pooling
functionality , is because each user must be authenticated against theoracle
database(security requirement)
and NOT against a LDAP server, and we are using a statefull backend(oraclepackages)
which would make it
difficult to reuse connections.
A problem that surfaced while doing heavy loadtesting with the customconnector,
>
is that sometimes connections are closed and new ones made in the midst ofa transaction.
If you imagine a scenario where a session bean creates a business entity,and
the session bean
calls 1 entity bean for the header and 1 entity bean for the detail, thenthe
header and detail
must be created in the same transaction AND with the same connection(thereis
a parent-child relationship
between header and detail enforced on the back end database via Primaryand Foreing
Keys).
We have not yet found why weblogic is closing the connection!
A second problem that we are experincing with the custom connector, is theuse
of CMP(container managed persistence)
within entity beans.
The J2EE developers state that the use of CMP decreases the develomenttime and
thus also maintenance costs.
We have not yet found a way to integrate a custom connector with the CMPpersistence
scheme !
In order to solve our loadtesting and CMP persistence problems i was askedto
come up with a solution
which should not use a custom connector,but use standard connection poolsfrom
weblogic.
To resolve the authentication problem on weblogic i could make a customrealm
which connects to the
backend database with the username and password, and if the connection isok ,
i could consider this
user as authenticated in weblogic.
That still leaves me with the problem of auditing and pooling.
If i were to use a standard connection pool,then all transaction made inthe oracle
database
would be done by a pool user or super user, a solution which will berejected
by our local security officer,
because you can not see which real user made a transaction in thedatabase.
I could still use the connection pool and in the application , advise theapplication
developers
to set an oracle package variable with the real user, then on arrival ofthe request
in the database,
the logic could use this package variable to set the transaction user.
There are still problems with this approach :
- The administrator of the database can still not see who is connected ,he will
only see the superuser connection.
- This scheme can not be used when you want to use CMP persistence , sinceit
is weblogic who will generate the code
to access the database.
I thought i had a solution when oracle provided us with a connection poolknown
as OracleOCIConnectionPool
where there is a connection made by a superuser, but where sessions aremultiplexed
over this physical pipe with the real user.
I can not seem to properly integrate this OCI connectionpool intoweblogic.
When using this pool , and we are coming into a bean (session or entitybean)
weblogic is wrapping
this pool with it's own internal Datasource and giving me back aconnection of
the superuser, but not one for the real user,
thus setting me with my back to the wall again.
I would appreciate if anyone had experienced the same problem to share apossible
solution with us
in order to satisfy all requirements(security,auditing,CMP).
Many Thanks
Blyau Gino
[email protected]

Why would connection pooling cause problems with a trigger?

This is a strange one. We have an app that deletes a row in a database table, and this table has a delete trigger on it. The row gets deleted every time the app is run, yet the trigger only fires intermittently. It's not that the trigger is failiing in some way - it just doesn't get called at all. If I issue the same delete command in PL/SQL developer then the trigger fires every time.
Several hours later and out of desparation I tried turning off connection pooling via the app's connection string, and found that the trigger now fires every time. Any ideas what might be causing this behaviour? I can reproduce/fix the issue every time simply by setting "Pooling" to true or false!
We are using Oracle 11g and ODP.Net v4.112.2.0.
Thanks in advance
Andrew

More information: I've now been able to reproduce this issue in a small .Net app, and can make it fail in a more consistent manner (which I'll explain later). While it's still too large to post the entire code here, I can summarise what the app does in pseudo-code:-
for(int i = 1; i <= 10; i++) // Run the test a number of times
// Step 1 - Delete rows from the table with the delete query in question
Execute non-query "delete from test_table";
Wait 1 second
// Step 2 - Check that the delete actually happened
Execute reader "select count(*) from test_table"
Display the count
// Step 3 - Check that the delete trigger inserted some rows into a "logging" table. This is my method of "tracing" - I added a basic insert to the start of each trigger section, as mentioned in my previous post.
Execute reader "select count(*) from my_logging_table"
Display the count
// Reinstate the test data
Execute non-query "<insert rows back into test_table>"
Wait 1 second
For info the connection string is fairly basic:- "Data Source=<tns name>;User Id=<foo>;Password=<bar>"
Some points of interest:-
- When running the above test app, the trigger successfully fires on the very first iteration (i.e. "Step 3" displays a non-zero count from the logging table). All subsequent iterations fail ("Step 3" displays the same count each time).
- If I turn off connection pooling (by adding "Pooling=false" to the connection string), the trigger runs on every iteration (i.e. "Step 3" displays an ever-incrementing record count).
- Regardless of whether it works or fails, the deletion in step 1 does take place (confirmed by "Step 2" displaying a count of zero).
- I added the waits after the non-query calls to see if that made a difference, but it doesn't. I can change these to 10 seconds or more and it will have no effect on the issue.
The "Execute non-query" method uses code along these lines:-
using (var conn = new OracleConnection(ConnString))
conn.Open();
using (var cmd = conn.CreateCommand())
cmd.CommandText = sql;
cmd.CommandType = CommandType.Text;
result = cmd.ExecuteNonQuery();
conn.Close();
return result;
While the "Execute reader" method looks like this:-
var conn = new OracleConnection(ConnString);
conn.Open();
var cmd = conn.CreateCommand();
cmd.CommandText = sql;
cmd.CommandType = CommandType.Text;
return cmd.ExecuteReader(CommandBehavior.CloseConnection);
The calling code in the for loop, wraps the returned reader in a using clause like this:-
using (var reader = ExecuteReader("<sql>"))
This will dispose of the reader, which will in turn close/dispose the connection (due to the CommandBehavior.CloseConnection parameter passed to ExecuteReader).
Interestingly, if the reader isn't disposed of then the problem becomes more intermittent (the trigger will fire perhaps 25% of the time). This is what's happening in our unit test harness. By ensuring the reader/connection is closed and disposed (which common sense would say should improve matters), the trigger only fires on the very first iteration of the loop. The plot thickens.

Questions regarding Connection Pooling

Hi
i have some confusion regarding how connection pooling is implemented..i have been doing some digging in to this lately but the more i read the more confused i get. i have some doubts here, will any of the posters here kindly clear them
a. Do i have to connect to my database via the DataSource method to take advantage of the connection pooling provided by my app server?..i have read conflicting information about this suggesting that Connection Pooling will not be provided to my app if i use DriverManager.getConnection()
b. if i chose to use the DataSource method do i have to implement the ConnectionPoolDataSource interface to provide the connection pooling for my app?
c. what is the best way to implement my own custom Connection pool?
Thanx

DriverManager.getConnection() literally creates, that is, builds a connection to the database using the values you previously supplied when you loaded the driver.
A connection pool is an object that contains several already made connections to the database, and simply provides you with one of those existing connections. The confusion arises because a) the method name is frequently the same and b) the connection pool object calls the driver's getConnection() method to create several connections before lending any of them out.
In other words:
DriverManager.getConnection() builds a connection to the database.
ConnectionPool.getConnection() fetches an existing connection.
So, to answer your questions...
A. This is correct. If you use DriverManager.getConnection(), you are indeed bypassing the Connection Pool entirely.
B. I'm not familiar with DataSource specifically, but in general, a third party connection pool will either give you the interface (and you implement the details) or they will give you the class file containing the DataSource object. All you would have to do in the latter case is to import that file, then create a new instance of it using the new keyword ( DataSource foo = new DataSource(); ). I suspect DataSource is indeed the class file.
C. Creating a connection pool is trivial and there are many examples of it - search on this forum or check out your favorite Java/JDBC programming book. Usually, the question "Should I use a connection pool and why?" is a more important question.

Connection Pooling in MOD_PLSQL

Hi,
I write an app with PL/SQL Web Toolkit using mod_plsql of Oracle HTTP server. I'd like to config connection pooling for this app. I read some docs but confused.
We have to config connection pooling or this feature is built-in feature that was configured already?
If we have to config, how to do?
Please help me.
Thanks a lot.

By default, this feature was configured already.

Connection Pooling in heavy traffic web-applications

In a 24x7 web-app used by 3000-10000 concurrent users, what is the
realistic number of maxmimum connections one should
have defined in the application server's connection pool?
The app has no caching mechanism therefore every page is a database
hit. Does max connection of 20 make sense when at any time 1000 users
could be using the web-app?
Is that number dictated by the DBA or the Java app developer?
For example, web sites like Amazon.com sure must be using connection
pools to control access to resources. Do they define 20 max connections
or 200 max connections to their database? Do they have multiple replicated databases, how are the databases synced up.

If I were to rephrase this question like
In Weblogic 7.0, if my connection pool has
1. Minimum capacity = 10
2. Maximum capacity = 100
3. Capacity Increment = 1
And say 100 users are connected to my site using all 100 connections available.
What happens to the 101th user?
1. Will he be waiting for the connection to be free which was held up by 100 users?
2. Will he get a Error/Exception regarding the same?
Rgds,
Seetesh

How to use connection pooling in 6.5 from standalone application?

Hi,
Is it possible to standalone application get connection from connection pool Sun ONE App Server 6.5?
If can means how pls tell me the steps?
I am trying standalone application to get connection from pool it will throw StackOverflowError.
thanks
with regds
parthi

Hi,
Is it possible to standalone application get connection from connection pool Sun ONE App Server 6.5?
If can means how pls tell me the steps?
I am trying standalone application to get connection from pool it will throw StackOverflowError.
thanks
with regds
parthi

Different connection pool for a report

Hi experts,
For one my reports using 'CLOBS' like explained (http://oraclebizint.wordpress.com/2007/11/12/oracle-bi-ee-101332-working-with-clob-fields/) I need to disable parallel processing because it's not supported.
NO_PARALLEL and NO_INDEX_PARALLEL hints at the query level couldn't disable the parallelism.the optimizer still use it.
I thought about having a new connection pool that contains 'before query' and 'after query' statements that will disable the parallelism.This will take me a lot of time to rebuild the whole Presentation and Business layers to point to a new physical tables.
Any one has an idea about how I can use another connection pool for a specific report?
Regards

I have the problem. My issue is that I need to have a webservice use the 2 database connection pools I have created. Originally the pools were Non-XA. When I change them to XA I cannot get the JMS JDBC Store to work.
java.lang.Exception: WebLogic Pool Driver doesn't support XA driver, Please change your config to use a Non-XA driver
However, part of what you wrote below I don't understand. You said you configured a brand new JMS JDBC Store and was able to use an XA Connection Pool? I tried to delete my existing one and create it anew, but was not able to use an XA pool.
Is there any solution around this? I need to have an XA Pool for a webservice but non-XA for my JMS Store.
"After much digging I found documentation that you cannot configure an XA JDBC Connection Pool for use with a JMS JDBC Store: http://edocs.bea.com/wls/docs81/ConsoleHelp/jms_config.html#1128929
The only thing is that if I configure a brand new JMS JDBC Store and make it use the XA JDBC Connection Pool (instead of just selecting the new MySQLXAConnPool from the list that includes the non XA pool) it works without an error."

Unable to get the expected results with connection pooling

Hi All,
I have been trying to create JDBC connection pooling provided by the Apache Tomcat 4.0 with MySQL 4.0.16-nt at http://jakarta.apache.org/tomcat/tomcat-4.1-doc/jndi-datasource-examples-howto.html and my configuration is as follows
server.xml
<Context path="/DBTest" docBase="DBTest"
debug="5" reloadable="true" crossContext="true">
<Logger className="org.apache.catalina.logger.FileLogger"
prefix="localhost_DBTest_log." suffix=".txt"
timestamp="true"/>
<Resource name="jdbc/TestDB"
auth="Container"
type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/TestDB">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>

<parameter>
<name>maxActive</name>
<value>100</value>
</parameter>

<parameter>
<name>maxIdle</name>
<value>30</value>
</parameter>

<parameter>
<name>maxWait</name>
<value>10000</value>
</parameter>

<parameter>
<name>username</name>
<value>javauser</value>
</parameter>
<parameter>
<name>password</name>
<value>javadude</value>
</parameter>

<parameter>
<name>driverClassName</name>
<value>org.gjt.mm.mysql.Driver</value>
</parameter>

<parameter>
<name>url</name>
<value>jdbc:mysql://localhost:3306/javatest?autoReconnect=true</value>
</parameter>
</ResourceParams>
</Context>
web.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<description>MySQL Test App</description>
<resource-ref>
<description>DB Connection</description>
<res-ref-name>jdbc/TestDB</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
</web-app>
test.jsp
<jsp:useBean id="foo" class="foo.DBTest" scope="page" />
<html>
<head>
<title>DB Test</title>
</head>
<body>
<%
foo.DBTest tst = new foo.DBTest();
tst.init();
%>
<h2>Results</h2>
Foo <%= tst.getFoo() %>
Bar <%= tst.getBar() %>
</body>
</html>
DBTest.java package
package foo;
import javax.naming.*;
import javax.sql.*;
import java.sql.*;
public class DBTest {
String foo = "Not Connected";
int bar = -1;
public void init() {
try{
Context ctx = new InitialContext();
if(ctx == null )
throw new Exception("Boom - No Context");
DataSource ds =
(DataSource)ctx.lookup(
"java:comp/env/jdbc/TestDB");
if (ds != null) {
Connection conn = ds.getConnection();
if(conn != null) {
foo = "Got Connection "+conn.toString();
Statement stmt = conn.createStatement();
ResultSet rst =
stmt.executeQuery(
"select id, foo, bar from testdata");
if(rst.next()) {
foo=rst.getString(2);
bar=rst.getInt(3);
conn.close();
}catch(Exception e) {
e.printStackTrace();
public String getFoo() { return foo; }
public int getBar() { return bar;}
Now when I am trying to run this on browser, everything goes fine except it doesn't show the expected results, instead of that it shows following in the browser:-
Results
Foo Not Connected
Bar -1
Can anybody help me out as to why I am getting such result while everything is right from my side. Is the program unable to connect to the database or it is not supporting the JDBC version that I am using.
Thanks in advance
Regards
Vikas

Oh, I think this is not the right place to post this message. I have placed the same in other place of this forum. please ignore this post here!!
MJ, by the way the link that you suggested is not useful to me.
Thank you

Connection pooling in multithreaded app results in occasional "Closed Statement" exc"

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