The cost of checking the connection when using JdbcPooledConnectionSource

Question

There is possible to let Ormlite check the connection before it will be handed over to the user when using JdbcPooledConnectionSource like this:

JdbcPooledConnectionSource connectionSource =
     new JdbcPooledConnectionSource("jdbc:h2:mem:account");
connectionSource.setTestBeforeGet(true);

What is the performance cost to let Ormlite do the checking? Why would I not let the Ormlite check the connection?

Answer 1

What is the performance cost to let Ormlite do the checking?

You can take a look at the source for the JdbcPooledConnectionSource. In the testConnection(...) method it effectively does:

connMetaData.connection.queryForLong(`SELECT 1`);

As to what the performance is, that would depend on a number of factors. This is doing a RPC with your database server but should not be hitting any disk on the server. So on a modern system we are probably talking about 10s of milliseconds – maybe less.

I think the best way to evaluate the cost of this is to turn it on and test your application and then turn it off and see if you notice a difference.

Why would I not let the Ormlite check the connection?

The reason why the setting is there is to protect against a pooled connection failing right when you go to use it. I would say that using it is conservative.

The JdbcPooledConnectionSource gives you other ways to verify the connection that aren't every time you go to get a pooled one. For example, if you call setCheckConnectionsEveryMillis(...) to some non-0 value, it will fork a thread to test the connections every so often. 60000 will have the thread do the SELECT 1 in the background which should not slow your application down.