LettuceConnectionFactory.destroy(…) releases cluster connections after shutting down the connection pool

[fightchwang]

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

Lines 545 to 570 in 1475069

	public RedisClusterCommands<byte[], byte[]> getResourceForSpecificNode(RedisClusterNode node) {
	Assert.notNull(node, "Node must not be null!");
	if (connection == null) {
	synchronized (this) {
	if (connection == null) {
	this.connection = connectionProvider.getConnection(StatefulRedisClusterConnection.class);
	}
	}
	}
	return connection.getConnection(node.getHost(), node.getPort()).sync();
	}
	@Override
	@SuppressWarnings("unchecked")
	public void returnResourceForSpecificNode(RedisClusterNode node, Object resource) {}
	@Override
	public void destroy() throws Exception {
	if (connection != null) {
	connectionProvider.release(connection);
	}
	}
	}

if i execute RedisConnectionCommands::ping command via a redistemplate, then should this connection variable to be reset to null in the callback method returnResourceForSpecificNode ?

if not, then when the destroy callback was called druing spring exit , the connectionProvider was already closed, calling connectionProvider.release(connection); would result in exception :

Returned connection io.lettuce.core.cluster.StatefulRedisClusterConnectionImpl@2d3456b was either previously returned or does not belong to this connection provider, did i understand right?

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

Lines 145 to 165 in 1475069

	public void release(StatefulConnection<?, ?> connection) {
	GenericObjectPool<StatefulConnection<?, ?>> pool = poolRef.remove(connection);
	if (pool == null) {
	AsyncPool<StatefulConnection<?, ?>> asyncPool = asyncPoolRef.remove(connection);
	if (asyncPool == null) {
	throw new PoolException("Returned connection " + connection
	+ " was either previously returned or does not belong to this connection provider");
	}
	discardIfNecessary(connection);
	asyncPool.release(connection).join();
	return;
	}
	discardIfNecessary(connection);
	pool.returnObject(connection);
	}

[mp911de]

if i execute RedisConnectionCommands::ping command via a redistemplate, then should this connection variable to be reset to null in the callback method returnResourceForSpecificNode ?

LettuceClusterNodeResourceProvider uses a Lettuce cluster connection to obtain an individual connection to a cluster node to run a particular command. Lettuce internally manages the node connection lifecycle. In LettuceClusterNodeResourceProvider it matters to keep a cluster connection until the LettuceClusterConnection gets closed.

The problem that you see is an ordering issue without real impact, it's mostly logging an exception.

Shutting down LettuceConnectionFactory first closes all connection providers, cleaning out the connection pools. Once the pools are closed, the clusterCommandExecutor holding a connection attempts to return (close) its connection. That disposal leads to the PoolException along with logging.

We need to fix the issue.

[fightchwang]

@mp911de thx for your reply, as you said, it's an ordering issue without real impact, it's mostly logging an exception.