possible bad side effects from change to AbstractConnectionManager

[mandrosen]

After migrating from jboss4 to jboss7 (currently jboss-as-7.1.1Final), we started seeing the error 'Unable to get managed connection' during certain high load periods using the same size pool that we were using in jboss4.  I put more details in this discussion: https://community.jboss.org/thread/214179

It seemed that there should still have been available connections while we got this error because MySQL showed the connections as sleeping.  I was looking at the code where the error is being thrown org.jboss.jca.core.connectionmanager.AbstractConnectionManager (ironjacamar-core-impl-1.0.9.Final.jar) at line 329.   I added one call that seems to help a little with our application, but I'm unsure if the benefits outweigh any negative side effects.

After line 333, failure = e; I added a pool flush.  Here is the diff:

334a335,336

>          pool.flush(true);

>

The flush seems to release the connection that wasn't sleeping so it can be used again.

Is there a better way to accomplish this?

[jesper.pedersen]

First of all - you should be using a nightly snapshot.

Then look into the <validation> element and provide the plugins needed (MySQL), and do <flush-strategy>IdleConnections</flush-strategy>

If you still have errors after that I would need to see TRACE log from org.jboss.jca and your full configuration.

[mandrosen]

I will test it with the nightly snapshot, but I have been using the validation plugins and the flush strategy.  I'll let you know what happens with the snapshot.

[mandrosen]

I am going to test with 1.0.13.Final, 1.1.0.Beta3, and then if those don't work, I can try the head version (is there a repository with nightly builds or should I just build it myself). 

My question is which version of jboss are those built against.  When I used 1.0.13.Final, I am getting this error:

Caused by: java.lang.ClassNotFoundException: org.jboss.jca.common.api.metadata.ds.DataSource$Tag from [Module "org.jboss.as.connector:main" from local module loader @538d7ace (roots: /usr/java/jboss/modules)]

so I will update the org.jboss.as.connector module, but I want to make sure I am using the correct version.

Thanks for your help.  I really appreciate it.

[jesper.pedersen]

IronJacamar 1.1 is for EE 7.

AS7/master already contains IJ 1.0.13... so you just need the latest nightly snapshot

[mandrosen]

I had the same issue with the latest jboss snapshot: jboss-as-7.2.0.Alpha1-SNAPSHOT

The trace is attached.

My datasource config:

                <datasource jta="true" jndi-name="java:jboss/datasources/atDS" pool-name="MySqlDS" enabled="true" spy="true" use-ccm="true">

                    <connection-url>jdbc:mysql://dbserv:3306/db</connection-url>

                    <driver-class>com.mysql.jdbc.Driver</driver-class>

                    <driver>mysql-connector-java-5.1.22-bin.jar</driver>

                    <transaction-isolation>TRANSACTION_READ_COMMITTED</transaction-isolation>

                    <pool>

                        <min-pool-size>0</min-pool-size>

                        <max-pool-size>1</max-pool-size>

                        <prefill>true</prefill>

                        <use-strict-min>true</use-strict-min>

                        <flush-strategy>IdleConnections</flush-strategy>

                    </pool>

                    <security>

                        <user-name>user</user-name>

                        <password>passwd</password>

                    </security>

                    <validation>

                        <valid-connection-checker class-name="org.jboss.jca.adapters.jdbc.extensions.mysql.MySQLValidConnectionChecker"/>

                        <stale-connection-checker class-name="org.jboss.jca.adatpers.jdbc.extensions.mysql.MySQLStaleConnectionChecker"/>

                        <exception-sorter class-name="org.jboss.jca.adapters.jdbc.extensions.mysql.MySQLExceptionSorter"/>

                    </validation>

                    <timeout>

                        <allocation-retry>3</allocation-retry>

                    </timeout>

                </datasource>

[jesper.pedersen]

I'm not seeing anything here. If you only have 1 connection available, then requests will timeout.

[mandrosen]

Thanks for looking into this.

When you say the requests, are you referring to the requests for a connection?

When mysql shows the connection as sleeping, but we still get the error, unable to retrieve managed connection, does that mean something is holding on to the connection?

[jesper.pedersen]

You have <max-pool-size> at 1 - it doesn't matter how many the connections the database is configured for.

Your log shows that the app gives up after 30 seconds to get a connection, which is default.

Your prefill at true doesn't do anything, since your <min-pool-size> is 0.

http://docs.jboss.org/ironjacamar/userguide/1.0/en-US/html/deployment.html#deployingds_descriptor

[mandrosen]

Very true, the prefill is left over from other configs -- useless in this test.

I did try increasing the blocking-timeout (default 30), but it just waits longer to timeout.

It seems stable and working with the increased number of connections.  I am curious about that one connection, but it's ok for now.

Thanks for your help.