Use before assignment of asyncDedicatedConnection in LettuceConnection

[oldium]

I found issue while reading how Lettuce integration works in this method:

spring-data-redis/src/main/java/org/springframework/data/redis/connection/lettuce/LettuceConnection.java

Lines 966 to 975 in 777f079

	protected StatefulConnection<byte[], byte[]> doGetAsyncDedicatedConnection() {
	StatefulConnection<byte[], byte[]> connection = getConnectionProvider().getConnection(StatefulConnection.class);
	if (customizedDatabaseIndex()) {
	potentiallySelectDatabase(this.dbIndex);
	}
	return connection;
	}

The method creates a new connection, which is stored by the caller into a asyncDedicatedConnection attribute:

spring-data-redis/src/main/java/org/springframework/data/redis/connection/lettuce/LettuceConnection.java

Lines 1026 to 1033 in 777f079

	private StatefulConnection<byte[], byte[]> getOrCreateDedicatedConnection() {
	if (this.asyncDedicatedConnection == null) {
	this.asyncDedicatedConnection = doGetAsyncDedicatedConnection();
	}
	return this.asyncDedicatedConnection;
	}

But it looks like the asyncDedicatedConnection is used before assignment in potentiallySelectDatabase() called by doGetAsyncDedicatedConnection():

spring-data-redis/src/main/java/org/springframework/data/redis/connection/lettuce/LettuceConnection.java

Lines 1068 to 1073 in 777f079

	private void potentiallySelectDatabase(int dbIndex) {
	if (asyncDedicatedConnection instanceof StatefulRedisConnection<byte[], byte[]> statefulConnection) {
	statefulConnection.sync().select(dbIndex);
	}
	}

[mp911de]

This is a bug, good catch. We need to apply the database selection clearly on the newly created connection. Do you want to submit a pull request?

[oldium]

Please do it if you have time :-)

[oldium]

Turns out the logic is broken here. select() refuses to use shared connection, so it executes the select command on a dedicated connection. This means that the potentiallySelectDatabase() call is superfluous in doGetAsyncDedicatedConnection, because the database change will be executed in select call anyway.

I am not able to tell the difference between connection.sync().select() (used in potentiallySelectDatabase method) and invokeStatus().just(..., CommandType.SELECT, ...) (used in select method), though.

[oldium]

Please check oldium@e47545a for possible fix. As I said, I am not sure whether the invokeStatus() (it uses RedisClusterAsyncCommands::dispatch, which is actually BaseRedisAsyncCommands::dispatch) is comparable/equivalent to connection.sync().select() call.