Initializing C3P0 connection pool takes 2 min

问题

I can't wrap my head around why the initialization of a c3p0 connection pool takes 2 min in my Hibernate application.

This is in my Hibernate.cfg.xml:

<hibernate-configuration>
    <session-factory>
        <property name="connection.driver_class">org.postgresql.Driver</property>
        <property name="connection.url"/>
        <property name="connection.default_schema"/>
        <property name="connection.username"/>
        <property name="connection.password"/> 

        <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>
        <property name="current_session_context_class">thread</property>

        <property name="hibernate.c3p0.acquire_increment">1</property>
        <property name="hibernate.c3p0.min_size">3</property>
        <property name="hibernate.c3p0.max_size">10</property>
        <property name="hibernate.c3p0.timeout">300</property>
        <property name="hibernate.c3p0.max_statements">50</property>
        <property name="hibernate.c3p0.idle_test_period">3000</property>
        <property name="hibernate.c3p0."></property>

        <property name="show_sql">true</property>
        <property name="format_sql">false</property>

        <property name="hbm2ddl.auto">create</property>
 </session-factory>
</hibernate-configuration>

The connection settings are set in my HibernateUtil file when building the session factory.

The pool is initialize when the first transaction in my tests is openend. Connecting and querying the db works just fine afterwards, it only hangs on the following line for a while before it will start. I formated the output a bit as I assume the problem may be with one of the settings mentioned here.:

INFO: Initializing c3p0 pool... 
com.mchange.v2.c3p0.PoolBackedDataSource@30670080 [
  connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@ecfec4d0 [
    acquireIncrement -> 1,
    acquireRetryAttempts -> 30,
    acquireRetryDelay -> 1000,
    autoCommitOnClose -> false,
    automaticTestTable -> null,
    breakAfterAcquireFailure -> false,
    checkoutTimeout -> 0,
    connectionCustomizerClassName -> null,
    connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester,        
    debugUnreturnedConnectionStackTraces -> false,
    factoryClassLocation -> null,
    forceIgnoreUnresolvedTransactions -> false,
    identityToken -> I-REMOVED-THIS,
    idleConnectionTestPeriod -> 3000,
    initialPoolSize -> 3,
    maxAdministrativeTaskTime -> 0,
    maxConnectionAge -> 0,
    maxIdleTime -> 300,
    maxIdleTimeExcessConnections -> 0,
    maxPoolSize -> 10,
    maxStatements -> 50,
    maxStatementsPerConnection -> 0,
    minPoolSize -> 3,
    nestedDataSource -> com.mchange.v2.c3p0.DriverManagerDataSource@b17e5c65 [
      description -> null,
      driverClass -> null,
      factoryClassLocation -> null,
      identityToken -> I-REMOVED-THIS,
      jdbcUrl -> jdbc:postgresql://URL-TO-MY_DB,
      properties -> {user=******, password=******, default_schema=}
    ],
    preferredTestQuery -> null,
    propertyCycle -> 0,
    testConnectionOnCheckin -> false,
    testConnectionOnCheckout -> false,
    unreturnedConnectionTimeout -> 0,
    usesTraditionalReflectiveProxies -> false;
    userOverrides: {}
  ],
  dataSourceName -> null,
  factoryClassLocation -> null,
  identityToken -> I-REMOVED-THIS,
  numHelperThreads -> 3
]

It's the first time I'm using Hibernate and c3p0 and I was expecting it to be much quicker when starting the pool? Is it a misconception of mine?

It's no difference between using the remote DB nor a local PostgreSQL instance.

(Edit: This is not true. I made a mistake when comparing local and remote db server. Locally, initialization is pretty much immediately, remotely it takes around 2 minutes.)

Edit2: Here is a log of the connection process.

回答1:

Set the property Hibernate.temp.use_jdbc_metadata_defaults to false in the configuration of your session factory. This will indicate to Hibernate using metadata dialect instead of the connection, which makes the slow startup. You must also configure an appropriate dialect for your driver.

来源：https://stackoverflow.com/questions/14417692/initializing-c3p0-connection-pool-takes-2-min