How to use Lettuce in Redis

1. Summary

Lettuce is an advanced Java client for Redis. It has become one of the most popular clients alongside Jedis. It has now become the default redis client in SpringBoot 2.0 version.

Compared with the veteran Jedis, Lettuce is a rising star. It is not only rich in functions, but also provides many new features, such as asynchronous operations, reactive programming, etc., and also solves the thread insecurity problem in Jedis.

2. Lettuce

2.1. Basic use

First, create a maven project, introduce the lettuce-core package, and you can use it.

<dependency>
  <groupId>io.lettuce</groupId>
  <artifactId>lettuce-core</artifactId>
  <version>5.3.1.RELEASE</version>
</dependency>

Use lettuce to connect to redis and test whether the connection can be normal!

public class LettuceMain {

    public static void main(String[] args) {
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1")
                .withPort(6379)
                .withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        RedisClient redisClient = RedisClient.create(redisUri);
        StatefulRedisConnection<String, String> connection = redisClient.connect();
        RedisCommands<String, String> commands = connection.sync();
        System.out.println(commands.ping());
        connection.close();
        redisClient.shutdown();
    }
}

2.2. Synchronous operations

Basically, Lettuce supports all synchronous command operations supported by Jedis.

Below, we take the synchronous operation of strings as an example. Lettuce's api operation is as follows!

public class LettuceSyncMain {

    public static void main(String[] args) {
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1").withPort(6379).withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        RedisClient redisClient = RedisClient.create(redisUri);
        StatefulRedisConnection<String, String> connection = redisClient.connect();
        //获取同步操作命令工具
        RedisCommands<String, String> commands = connection.sync();

        System.out.println("清空数据："+commands.flushdb());
        System.out.println("判断某个键是否存在："+commands.exists("username"));
        System.out.println("新增<&#39;username&#39;,&#39;xmr&#39;>的键值对："+commands.set("username", "xmr"));
        System.out.println("新增<&#39;password&#39;,&#39;password&#39;>的键值对："+commands.set("password", "123"));
        System.out.println("获取<&#39;password&#39;>键的值："+commands.get("password"));
        System.out.println("系统中所有的键如下：" + commands.keys("*"));
        System.out.println("删除键password:"+commands.del("password"));
        System.out.println("判断键password是否存在："+commands.exists("password"));
        System.out.println("设置键username的过期时间为5s:"+commands.expire("username", 5L));
        System.out.println("查看键username的剩余生存时间："+commands.ttl("username"));
        System.out.println("移除键username的生存时间："+commands.persist("username"));
        System.out.println("查看键username的剩余生存时间："+commands.ttl("username"));
        System.out.println("查看键username所存储的值的类型："+commands.type("username"));

        connection.close();
        redisClient.shutdown();
    }
}

2.3. Asynchronous operations

In addition, Lettuce also supports asynchronous operations. Change the above operations to asynchronous processing. The results are as follows!

public class LettuceASyncMain {

    public static void main(String[] args) throws Exception {
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1").withPort(6379).withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        RedisClient redisClient = RedisClient.create(redisUri);
        StatefulRedisConnection<String, String> connection = redisClient.connect();
        //获取异步操作命令工具
        RedisAsyncCommands<String, String> commands = connection.async();

        System.out.println("清空数据："+commands.flushdb().get());
        System.out.println("判断某个键是否存在："+commands.exists("username").get());
        System.out.println("新增<&#39;username&#39;,&#39;xmr&#39;>的键值对："+commands.set("username", "xmr").get());
        System.out.println("新增<&#39;password&#39;,&#39;password&#39;>的键值对："+commands.set("password", "123").get());
        System.out.println("获取<&#39;password&#39;>键的值："+commands.get("password").get());
        System.out.println("系统中所有的键如下：" + commands.keys("*").get());
        System.out.println("删除键password:"+commands.del("password").get());
        System.out.println("判断键password是否存在："+commands.exists("password").get());
        System.out.println("设置键username的过期时间为5s:"+commands.expire("username", 5L).get());
        System.out.println("查看键username的剩余生存时间："+commands.ttl("username").get());
        System.out.println("移除键username的生存时间："+commands.persist("username").get());
        System.out.println("查看键username的剩余生存时间："+commands.ttl("username").get());
        System.out.println("查看键username所存储的值的类型："+commands.type("username").get());

        connection.close();
        redisClient.shutdown();
    }
}

2.4. Reactive programming

In addition to supporting asynchronous programming, Lettuce also supports reactive programming. The reactive programming framework introduced by Lettuce is Project Reactor. If not You can learn about reactive programming experience by yourself first.

Reactive programming use cases are as follows:

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1").withPort(6379).withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        RedisClient redisClient = RedisClient.create(redisUri);
        StatefulRedisConnection<String, String> connection = redisClient.connect();
        //获取响应式API操作命令工具
        RedisReactiveCommands<String, String> commands = connection.reactive();

        Mono<String> setc = commands.set("name", "mayun");
        System.out.println(setc.block());
        Mono<String> getc = commands.get("name");
        getc.subscribe(System.out::println);
        Flux<String> keys = commands.keys("*");
        keys.subscribe(System.out::println);

        //开启一个事务，先把count设置为1，再将count自增1
        commands.multi().doOnSuccess(r -> {
            commands.set("count", "1").doOnNext(value -> System.out.println("count1：" +  value)).subscribe();
            commands.incr("count").doOnNext(value -> System.out.println("count2：" +  value)).subscribe();
        }).flatMap(s -> commands.exec())
                .doOnNext(transactionResult -> System.out.println("transactionResult：" + transactionResult.wasDiscarded())).subscribe();

        Thread.sleep(1000 * 5);
        connection.close();
        redisClient.shutdown();
    }
}

2.5. Publishing and subscribing

Lettuce also supports redis message publishing and subscription. The specific implementation cases are as follows:

public class LettuceReactiveMain1 {

    public static void main(String[] args) throws Exception {
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1").withPort(6379).withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        RedisClient redisClient = RedisClient.create(redisUri);
        //获取发布订阅操作命令工具
        StatefulRedisPubSubConnection<String, String> pubsubConn = redisClient.connectPubSub();
        pubsubConn.addListener(new RedisPubSubListener<String, String>() {
            @Override
            public void unsubscribed(String channel, long count) {
                System.out.println("[unsubscribed]" + channel);
            }
            @Override
            public void subscribed(String channel, long count) {
                System.out.println("[subscribed]" + channel);
            }
            @Override
            public void punsubscribed(String pattern, long count) {
                System.out.println("[punsubscribed]" + pattern);
            }
            @Override
            public void psubscribed(String pattern, long count) {
                System.out.println("[psubscribed]" + pattern);
            }
            @Override
            public void message(String pattern, String channel, String message) {
                System.out.println("[message]" + pattern + " -> " + channel + " -> " + message);
            }
            @Override
            public void message(String channel, String message) {
                System.out.println("[message]" + channel + " -> " + message);
            }
        });
        RedisPubSubAsyncCommands<String, String> pubsubCmd = pubsubConn.async();
        pubsubCmd.psubscribe("CH");
        pubsubCmd.psubscribe("CH2");
        pubsubCmd.unsubscribe("CH");

        Thread.sleep(100 * 5);
        pubsubConn.close();
        redisClient.shutdown();
    }
}

2.6. Client resources and parameter configuration

The communication framework of Lettuce client integrates Netty’s non-blocking IO operations. The setting of client resources is closely related to Lettuce’s performance, concurrency and event processing. If not I am particularly familiar with client parameter configuration. It is not recommended to modify the default values ​​intuitively without experience. Just keep the default configuration.

In a non-cluster environment, the specific configuration examples are as follows:

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        ClientResources resources = DefaultClientResources.builder()
                .ioThreadPoolSize(4) //I/O线程数
                .computationThreadPoolSize(4) //任务线程数
                .build();
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1").withPort(6379).withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        ClientOptions options = ClientOptions.builder()
                .autoReconnect(true)//是否自动重连
                .pingBeforeActivateConnection(true)//连接激活之前是否执行PING命令
                .build();
        RedisClient client = RedisClient.create(resources, redisUri);
        client.setOptions(options);
        StatefulRedisConnection<String, String> connection = client.connect();
        RedisCommands<String, String> commands = connection.sync();
        commands.set("name", "关羽");
        System.out.println(commands.get("name"));

        connection.close();
        client.shutdown();
        resources.shutdown();
    }
}

In a cluster environment, the specific configuration examples are as follows:

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        ClientResources resources = DefaultClientResources.builder()
                .ioThreadPoolSize(4) //I/O线程数
                .computationThreadPoolSize(4) //任务线程数
                .build();
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1").withPort(6379).withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        ClusterClientOptions options = ClusterClientOptions.builder()
                .autoReconnect(true)//是否自动重连
                .pingBeforeActivateConnection(true)//连接激活之前是否执行PING命令
                .validateClusterNodeMembership(true)//是否校验集群节点的成员关系
                .build();
        RedisClusterClient client = RedisClusterClient.create(resources, redisUri);
        client.setOptions(options);
        StatefulRedisClusterConnection<String, String> connection = client.connect();
        RedisAdvancedClusterCommands<String, String> commands = connection.sync();
        commands.set("name", "张飞");
        System.out.println(commands.get("name"));

        connection.close();
        client.shutdown();
        resources.shutdown();
    }
}

2.7, Thread pool configuration

Lettuce connections are designed to be thread-safe, so a connection can be shared by multiple threads. At the same time, lettuce connections are automatically reconnected by default. Using a single connection can basically meet business needs. In most cases, there is no need to configure the connection. Pooling and multiple connections will not bring performance improvement to the operation.

But in some special scenarios, such as transaction operations, using a connection pool would be a better solution. So how to configure the thread pool?

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        RedisURI redisUri = RedisURI.builder()
                .withHost("127.0.0.1")
                .withPort(6379)
                .withPassword("111111")
                .withTimeout(Duration.of(10, ChronoUnit.SECONDS))
                .build();
        RedisClient client = RedisClient.create(redisUri);
        //连接池配置
        GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
        poolConfig.setMaxIdle(2);

        GenericObjectPool<StatefulRedisConnection<String, String>> pool = ConnectionPoolSupport.createGenericObjectPool(client::connect, poolConfig);
        StatefulRedisConnection<String, String> connection = pool.borrowObject();
        RedisCommands<String, String> commands = connection.sync();
        commands.set("name", "张飞");
        System.out.println(commands.get("name"));

        connection.close();
        pool.close();
        client.shutdown();
    }
}

2.8. Master-slave mode configuration

redis generally uses the master-slave replication mode to build a high-availability architecture. Simply put, there is one master node, multiple slave nodes, and automatic slave nodes. Sync the latest data.

Lettuce supports automatically discovering node information in master-slave mode and then saving it locally. The specific configuration is as follows:

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        //这里只需要配置一个节点的连接信息，不一定需要是主节点的信息，从节点也可以;可以自动发现主从节点
        RedisURI uri = RedisURI.builder().withHost("192.168.31.111").withPort(6379).withPassword("123456").build();
        RedisClient client = RedisClient.create(uri);
        StatefulRedisMasterReplicaConnection<String, String> connection = MasterReplica.connect(client, StringCodec.UTF8, uri);
        //从节点读取数据
        connection.setReadFrom(ReadFrom.REPLICA);

        RedisCommands<String, String> commands = connection.sync();
        commands.set("name", "张飞");
        System.out.println(commands.get("name"));

        connection.close();
        client.shutdown();
    }
}

Of course, we can also manually specify the cluster node to load. The specific configuration is as follows:

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        //集群节点
        List<RedisURI> uris = new ArrayList();
        uris.add(RedisURI.builder().withHost("192.168.31.111").withPort(6379).withPassword("111111").build());
        uris.add(RedisURI.builder().withHost("192.168.31.112").withPort(6379).withPassword("111111").build());
        uris.add(RedisURI.builder().withHost("192.168.31.113").withPort(6379).withPassword("111111").build());

        RedisClient client = RedisClient.create();
        StatefulRedisMasterReplicaConnection<String, String> connection = MasterReplica.connect(client, StringCodec.UTF8, uris);
        //从节点读取数据
        connection.setReadFrom(ReadFrom.REPLICA);

        RedisCommands<String, String> commands = connection.sync();
        commands.set("name", "张飞");
        System.out.println(commands.get("name"));

        connection.close();
        client.shutdown();
    }
}

2.9. Sentinel mode configuration

Sentinel mode is also a highlight of redis in achieving high service availability. The specific configuration is as follows:

public class LettuceMain {

    public static void main(String[] args) throws Exception {
        //集群节点
        List<RedisURI> uris = new ArrayList();
        uris.add(RedisURI.builder().withSentinel("192.168.31.111", 26379).withSentinelMasterId("mymaster").withPassword("123456").build());
        uris.add(RedisURI.builder().withSentinel("192.168.31.112", 26379).withSentinelMasterId("mymaster").withPassword("123456").build());
        uris.add(RedisURI.builder().withSentinel("192.168.31.113", 26379).withSentinelMasterId("mymaster").withPassword("123456").build());

        RedisClient client = RedisClient.create();
        StatefulRedisMasterReplicaConnection<String, String> connection = MasterReplica.connect(client, StringCodec.UTF8, uris);
        //从节点读取数据
        connection.setReadFrom(ReadFrom.REPLICA);

        RedisCommands<String, String> commands = connection.sync();
        commands.set("name", "赵云");
        System.out.println(commands.get("name"));

        connection.close();
        client.shutdown();
    }
}

2.10. Cluster cluster mode configuration

Cluster cluster mode is a high-availability architecture model introduced later. It mainly uses sharding to store data. The specific configuration is as follows:

public class LettuceReactiveMain4 {

    public static void main(String[] args) throws Exception {
        Set<RedisURI> uris = new HashSet<>();
        uris.add(RedisURI.builder().withHost("192.168.31.111").withPort(7000).withPassword("123456").build());
        uris.add(RedisURI.builder().withHost("192.168.31.112").withPort(7000).withPassword("123456").build());
        uris.add(RedisURI.builder().withHost("192.168.31.113").withPort(7000).withPassword("123456").build());
        uris.add(RedisURI.builder().withHost("192.168.31.114").withPort(7000).withPassword("123456").build());
        uris.add(RedisURI.builder().withHost("192.168.31.115").withPort(7000).withPassword("123456").build());
        uris.add(RedisURI.builder().withHost("192.168.31.116").withPort(7001).withPassword("123456").build());

        RedisClusterClient client = RedisClusterClient.create(uris);
        StatefulRedisClusterConnection<String, String> connection = client.connect();
        RedisAdvancedClusterCommands<String, String> commands = connection.sync();
        commands.set("name", "关羽");
        System.out.println(commands.get("name"));

        //选择从节点,只读
        NodeSelection<String, String> replicas = commands.replicas();
        NodeSelectionCommands<String, String> nodeSelectionCommands = replicas.commands();
        Executions<List<String>> keys = nodeSelectionCommands.keys("*");
        keys.forEach(key -> System.out.println(key));

        connection.close();
        client.shutdown();
    }
}

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