the higher you fly

We came up with a not so un-common use-case of wanting to setup a Jedis connection pool that would automatically select a given database index on each connection. A colleague and I were about to patch the Spring-Data source code (we are already running a patched version), but instead found a very elegant solution by digging in a bit more:

The problem

The spring-data org.springframework.data.keyvalue.redis.connection.jedis.JedisConnectionFactory class offers no way to configure it to use a specific database. It defaults to database index 0 (in other words, does nothing on a new connection – so Redis automatically works on index 0).

Given that we will be running automated integration tests on a single Redis server instance, and that those tests will flush the database on each run (i.e.: select 2; flushdb), we needed an easy way to get a new connection factory instance that would first select the configured database index when a connection is created.

Without that database index selection, any integration tests running concurrently would flush or interfere with the data of the other running tests.

The solution

We simply extended the org.springframework.data.keyvalue.redis.connection.jedis.JedisConnectionFactory class and overrode the fetchJedisConnector() protected method:

public class MyCustomJedisConnectionPoolFactory extends JedisConnectionFactory {

private static final int DEFAULT_REDIS_DATABASE_INDEX = 0;

private int databaseIndex = 0;

@Override

protected Jedis fetchJedisConnector() {

Jedis jedis = super.fetchJedisConnector();

if (this.databaseIndex != DEFAULT_REDIS_DATABASE_INDEX) {

jedis.select(this.databaseIndex);

}

return jedis;

}

public void setDatabaseIndex(int databaseIndex) {

this.databaseIndex = databaseIndex;

}

}

The if statement isn’t strictly necessary in the fetchJedisConnector() method, but given that most of the time we will be using the default database, it seemed like it was worth it.