I use Hibernate together with
MySQL 5.1.30.
I have the next libraries:
-
c3p0-0.0.1.2.jar
-
mysql-connector-java-5.0.3-bin.jar
-
hibernate3.jar
I use a hibernate.cfg.xml for configuration:
Code:
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">org.gjt.mm.mysql.Driver</property>
<property name="connection.url">jdbc:mysql://localhost/fooDatatbase</property>
<property name="connection.username">foo</property>
<property name="connection.password">foo123</property>
<!-- Use the C3P0 connection pool provider -->
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.timeout">300</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_periods">3000</property>
<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<mapping resource="databaselayer/mail/Mail.hbm.xml"/>
<mapping resource="databaselayer/courses/Course.hbm.xml"/>
<mapping resource="databaselayer/price/Price.hbm.xml"/>
<mapping resource="databaselayer/contact/Contact.hbm.xml"/>
<mapping resource="databaselayer/artists/Musician.hbm.xml"/>
<mapping resource="databaselayer/concerts/Concert.hbm.xml"/>
<mapping resource="databaselayer/welcome/Welcome.hbm.xml"/>
<mapping resource="databaselayer/information/Information.hbm.xml"/>
</session-factory>
</hibernate-configuration>
In the
JAVA persistance with hibernate book, c3p0 configuration options are explained:
-
hibernate.c3p0.min_size This is the minimum number of JDBC connections that C3P0 keeps ready at all times
-
hibernate.c3p0.max_size This is the maximum number of connections in the pool. An exception is thrown at runtime if this number is exhausted.
-
hibernate.c3p0.timeout You specify the timeout period (in this case, 300 seconds) after which an idle connection is removed from the pool).
-
hibernate.c3p0.max_statements Maximum Number of statements that will be cached. Caching of prepared statements is essential for best performance with Hibernate.
-
hibernate.c3p0.idle\_test_periods This is the iddle time in seconds before a connection is automatically validated.
I use
Java 1.5.0_09 and
tomcat 6.0. I have three applications deployed in tomcat. Each of them uses hibernate with a configuration file almost equivalent the shown above (only username, databasename, password and the mapping resoruces change).
Unfortunately with the above settings, after some hours running i get some nasty **Deadlock errors** which end killing tomcat.
Code:
Jan 22, 2009 3:29:07 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@2437d -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Jan 22, 2009 3:29:07 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@1dc5cb7 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Jan 22, 2009 3:29:07 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@9cd2ef -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Jan 22, 2009 3:29:07 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@4af355 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Jan 22, 2009 3:29:07 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
WARNING: com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@1275fcb -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
Jan 22, 2009 3:29:35 PM com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector run
This seems to be an error several people already got. I changed my settings trying to follow the workaround described here
http://forum.hibernate.org/viewtopic.php?p=2386237 to:
Code:
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.min_size">0</property>
<property name="hibernate.c3p0.max_size">48</property>
<property name="hibernate.c3p0.timeout">0</property>
<property name="hibernate.c3p0.max_statements">0</property>
With the new settings, I do not get Deadlocks, but i get:
Code:
WARNING: SQL Error: 0, SQLState: 08S01
Jan 24, 2009 5:53:37 AM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.io.EOFException
STACKTRACE:
java.io.EOFException
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1913)
Does anyone knows what i am doing wrong, and how can i setup c3p0 correctly?
Thanks in advanced!
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