Unable to fill pool (no buffer space available)

Question

I'm using Wildfly 8.2 and fire a series of DB requests when a certain web page is opened. All queries are invoked thru JPA Criteria API, return results as expected - and - none of them delivers a warning, error or exception. It all runs in Parallel Plesk.

Now, I noticed that within 2 to 3 days the following error appears and the site becomes unresponsive. I restart and I wait approx another 3 days till it happens again (depending on the number of requests I have).

I checked the tcpsndbuf on my linux server and I noticed it is constantly at max. Unless I restart Wildfly. Apparently it fails to release the connections.

The connections are managed by JPA/Hibernate and the Wildfly container. I don't do any special or custom transaction handling e.g. open, close. etc. I leave it all to Wildfly.

The MySQL Driver I'm using is 5.1.21 (mysql-connector-java-5.1.21-bin.jar)

In the standalone.xml I have defined the following datasource datasource values (among others):

<transaction-isolation>TRANSACTION_READ_COMMITTED</transaction-isolation>
<pool>
    <min-pool-size>3</min-pool-size>
    <max-pool-size>10</max-pool-size>
</pool>
<statement>
     <prepared-statement-cache-size>32</prepared-statement-cache-size>
     <shared-prepared-statements>true</shared-prepared-statements>
</statement

Has anyone experience the same rise of tcpsndbuf values (or this error)? In case you require more config or log files, let me know. Thanks!

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UPDATE Despite the following additional timeout settings, it still runs into the hanger. And thus, it will then use 100% CPU time, whenever the max tcpsndbuf is reached.,

Answer 1

Try adding this Hibernate property:

<property name="hibernate.connection.release_mode">after_transaction</property>

By default, JTA mandates that connection should be released after each statement, which is undesirable for most use cases. Most Drivers don't allow multiplexing a connection over multiple XA transactions anyway.