I'm new on Open Liberty and I need to maintain a legacy app
I have on this app logs the following error:
The ConnectionManager was unable to associate Connection com.ibm.ws.rsadapter.jdbc.WSJdbcConnection#3b05f444 with ManagedConnection
WSRdbManagedConnectionImpl#67538473 for resource jdbc/AppDs. Received exception: com.ibm.ws.rsadapter.exceptions.DataStoreAdapterException:
DSRA9420E: Connection cannot be reassociated because child objects are still open.
I'm not sure from to start on this.
I have already searched here
But the code that is shown on logs is based on spring and it couldn't leak connections.
The app uses spring and ehcache.
Please, can someone to provide some guidance?
Looking at the Open Liberty source, that error is raised from a single place in the code, in response to the error condition that a JDBC Connection still has open child JDBC resources (such as Statement, PreparedStatement, ...) associated with it, at a point where it is being asked to reassociate the connection handle across transaction boundaries. Looking at the single caller of that code, it appears that the dissociate method (which closes these same JDBC resources) would have been invoked only a few lines earlier, suggesting that the only way for you to reach the state where the error occurs is if other code were simultaneously using the connection from another thread. To help confirm if this is the case, you could try enabling Liberty trace (via server.xml config) of
<logging traceSpecification="*=info:RRA=all"/>
while reproducing the error and post it somewhere accessible to look at.
Related
I have a servlet which connects to Oracle DB using JDBC (ojdbc6.jar) and BoneCP. I now need to port my BoneCP-using code to something which will work in WebLogic out-of-the-box, without having BoneCP in the package.
What would be the recommended approach? What WebLogic feature I can use, specifically to get an equivalent of BoneCP's:
Performance
Ability to log failed SQL statements
Auto-resume from lost DB connection
Thanks in advance.
The best approach would be to create a standard Oracle JDBC connection pool pointing to your database. Tune it according to your necessities (number of connections, etc.). Next you would need to refactor out of your code any explicit reference to your former connection pool implementation. If you have been working with java.sql.* interfaces in your code, there should be few to no references at all.
Once all that is refactorized, you will have only a bit of code (or config file) telling your app to recover something implementing javax.sql.DataSource from a given JNDI name and getting Connections out of it. The rest should be the same - just do whatever you need and close your ResultSets, Statements and Connections as you must have been doing until now.
About your questions, you will find extensive information on how to monitor your connection pool, and its fail recovery policies, here (depending on your app server version, I paste here the one I have used):
http://docs.oracle.com/cd/E15051_01/wls/docs103/jdbc_admin/jdbc_datasources.html
About performance, I have no accurate data nor benchmarks comparing both implementations; for your tranquility, I would say you that I have never found a database performance problem in the connection pool implementation - this does not mean that it cannot exist, but it is the last place I would look for it ;)
I am an Oracle DBA and not a java developer or websphere expert. We recently started using websphere in our environment. So the developers are still learning it. So I may not word my question properly. I did search the forums and saw 2 other questions like this. My question is more about how to trouble shoot this.
Websphere 8.5.0.2
Oracle 11.2.0.3
I see 20 open connections in the database. All are inactive. So they are not processing. From oracle it is v$session. Inactive means, you are open and not doing anything. Basically it is idle.
If they are inactive and not processing, they should be available for the connection pool to give to a new requester, assuming the DAO the java developer is using is being closed when done (this includes try/catch block). We confirmed that he is closing his connections.
Checks so far:
1. We reviewed the developers code. He is using standard java DAOs. He is closing his connection. He has a try/catch block and the first thing he does in the catch is close the connection.
2. My assumption is that this should cover the code path.
We don't see any errors raised in a log about 'closing' a connection.
My understanding of how a connection pool works
1. Pool Manager opens a configurable set of connections to the database. In our case it is 20.
2. When an application requests a connection, the connection manager does a lookup of the pool for the next available connection, then passes a pointer to that connect to the requesting function.
Possibility:
1. really slow server. We are using VMs for development/test. We do not have visibility to the servers to see if they are busy. So another VM could be using up CPU or disk.
Though lookups for available connections are light weight, it is possible that the server is hung up at 100% cpu and we timeout. Problem is, I don't have a way to look at this. No privileges and no access to someone who does.
not closing connections: We checked pretty thoroughly. We don't see any code passes (including exceptions) where he is not closing connections. First thing he does in a catch, is close the connection.
Any suggestions on where to look? I think its an issue with a slow server, but I want to rule other stuff out. I would like to state again that I am not a java developer or a websphere expert. So my question may be worded poorly.
the first thing he does in the catch is close the connection
Get the developer to introduce finally block after catch block and close connection in finally block, instead of catch block. Flow will move to catch only in case of error, but on normal flow the connection will not be released soon.
try {
//do something
}
catch(Exception ex) {
// log error
}
finally {
//close connection here
}
The symptoms you've described indicate a connection leak. Leaks are easy to solve (see ad-inf's response), but it can be hard to locate the source of the leak. Luckily, WAS comes with ConnLeakLogic mechanism. After enabling it, in the trace.log you'll find entries related to connections which have been retrieved from pool by application and haven't been returned for longer period of time. That connection information will also print a stack trace of a Java thread from the time of obtaining the connection. Seeing that stack traces, Java developer should be able to identify offending code.
C3p0 cache has acquireRetryDelay parameter to set time between acquire attempts.
Has tomcat7 jdbc-pool the same functionality?
No, tomcat jdbc pool does not automatically try to connect again, when the attempt to create a connection fails. It simply will throw the exception it got as an SQLException (if it was not one in the first place).
If it's you code which needs to do retry you can do it yourself, by trying to get connection several times. Or you might be able to make a patch, it does not seem to be so hard to do.
You can try to use some different libraries, they say BoneCP is quite good (although I never tried that).
During debugging my services code with uses Entity Framework for Oracle, I find that if I pause a little too long while examining code, the next time the connection is needed (I have a single context open during the entire transaction) I get an error stating that the provider could not be opened. Is there some sort of timeout in EF or the connection pool that I'm hitting? How can I tell and/or fix it?
We are running our Junit 4 test suite against Weblogic 9 in front of an Oracle 10 database (using Hudson as a continuous integration server) and occasionally we will get an ORA-12519 crash during script teardown. However, the error is very intermittent:
It usually happens for the same Test class
It doesn't always happen for the same test cases (sometimes they pass)
It doesn't happen for the same number of test cases (anywhere from 3-9)
Sometimes it doesn't happen at all, everything passes
While I can't guarantee this doesn't happen locally (when running against the same database, of course), I have run the same suite of class multiple times with no issues.
Any ideas?
Don't know if this will be everybody's answer, but after some digging, here's what we came up with.
The error is obviously caused by the fact that the listener was not accepting connections, but why would we get that error when other tests could connect fine (we could also connect no problem through sqlplus)? The key to the issue wasn't that we couldn't connect, but that it was intermittent
After some investigation, we found that there was some static data created during the class setup that would keep open connections for the life of the test class, creating new ones as it went. Now, even though all of the resources were properly released when this class went out of scope (via a finally{} block, of course), there were some cases during the run when this class would swallow up all available connections (okay, bad practice alert - this was unit test code that connected directly rather than using a pool, so the same problem could not happen in production).
The fix was to not make that class static and run in the class setup, but instead use it in the per method setUp and tearDown methods.
So if you get this error in your own apps, slap a profiler on that bad boy and see if you might have a connection leak. Hope that helps.
Another solution I have found to a similar error but the same error message is to increase the number of service handlers found. (My instance of this error was caused by too many connections in the Weblogic Portal Connection pools.)
Run SQL*Plus and login as SYSTEM. You should know what password you’ve used during the installation of Oracle DB XE.
Run the command alter system set processes=150 scope=spfile; in SQL*Plus OR any SQL friendly IDE.
VERY IMPORTANT: Restart the database, to make the change effective in the SPFILE.
From here:
http://www.atpeaz.com/index.php/2010/fixing-the-ora-12519-tnsno-appropriate-service-handler-found-error/
I also had the same problem, I searched for the answers many places. I got many similar answers to change the number of process/service handlers. But I thought, what if I forgot to reset it back?
Then I tried using Thread.sleep() method after each of my connection.close();.
I don't know how, but it's working at least for me.
If any one wants to try it out and figure out how it's working then please go ahead. I would also like to know it as I am a beginner in programming world.
I had this problem in a unit test which opened a lot of connections to the DB via a connection pool and then "stopped" the connection pool (ManagedDataSource actually) to release the connections at the end of the each test. I always ran out of connections at some point in the suite of tests.
Added a Thread.sleep(500) in the teardown() of my tests and this resolved the issue. I think that what was happening was that the connection pool stop() releases the active connections in another thread so that if the main thread keeps running tests the cleanup thread(s) got so far behind that the Oracle server ran out of connections. Adding the sleep allows the background threads to release the pooled connections.
This is much less of an issue in the real world because the DB servers are much bigger and there is a healthy mix of operations (not just endless DB connect/disconnect operations).
I had the similar issue. It happened every time when I run a pack of database (Spring JDBC) tests with SpringJUnit4ClassRunner, so I resolved the issue putting #DirtiesContext annotation for each test in order to cleanup the application context and release all resources thus each test could run with a new initalization of the application context.