Java client can't connect to Redis Sentinel which is running on localhost

Question

I have setup 3 Redis Server and 3 Redis Sentinel instances in my localhost. The servers are running at:

127.0.0.1:6379 // Master
127.0.0.1:6380 // Slave
127.0.0.1:6381 // Slave

and the sentinels are running at:

127.0.0.1:5000
127.0.0.1:5001
127.0.0.1:5002

I have a (Java) client that tries to connect to one of the sentinels and set the keys in redis server:

// import statements

public class RedisPush {

    private static final String MASTER_NAME = "mymaster";
    private static final String PASSWORD = "foobared";
    private static final Set sentinels;
    static {
        sentinels = new HashSet();
        sentinels.add("127.0.0.1:5000");
        sentinels.add("127.0.0.1:5001");
        sentinels.add("127.0.0.1:5002");
    }

    public static void pushToRedis() {

        Jedis jedis = null;

        try {
            JedisSentinelPool pool = new JedisSentinelPool(MASTER_NAME, sentinels);
            System.out.println("Fetching connection from pool.");
            jedis = pool.getResource();
            jedis.auth(PASSWORD);
            Socket socket = jedis.getClient().getSocket();

            System.out.println("Connected to " + socket.getRemoteSocketAddress());
            int i = 0;
            while (true) {
                jedis.set("sentinel_key" + i, "value" + i);
                System.out.println(i);
                i++;
                Thread.sleep(1000);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
        finally {
            if(jedis != null)
                jedis.close();
        }

    }

    public static void main(String[] args) throws Exception {

        while(true) {

            pushToRedis();
            Thread.sleep(1000);
        }
    }
}

Initially, my sentinel configuration is as follows (for example, the first sentinel running on port 5000):

bind 127.0.0.1
port 5000
sentinel monitor mymaster 127.0.0.1 6379 2
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 60000
sentinel auth-pass mymaster foobared

If I try to run my (Java) client, I get the following error:

Nov 23, 2018 1:52:57 AM redis.clients.jedis.JedisSentinelPool initSentinels
INFO: Trying to find master from available Sentinels...
Nov 23, 2018 1:52:57 AM redis.clients.jedis.JedisSentinelPool initSentinels
WARNING: Cannot get master address from sentinel running @ 192.168.0.102:5001. Reason: redis.clients.jedis.exceptions.JedisConnectionException: java.net.ConnectException: Connection refused (Connection refused). Trying next one.
Nov 23, 2018 1:52:57 AM redis.clients.jedis.JedisSentinelPool initSentinels
WARNING: Cannot get master address from sentinel running @ 192.168.0.102:5000. Reason: redis.clients.jedis.exceptions.JedisConnectionException: java.net.ConnectException: Connection refused (Connection refused). Trying next one.
Nov 23, 2018 1:52:57 AM redis.clients.jedis.JedisSentinelPool initSentinels
WARNING: Cannot get master address from sentinel running @ 192.168.0.102:5002. Reason: redis.clients.jedis.exceptions.JedisConnectionException: java.net.ConnectException: Connection refused (Connection refused). Trying next one.
redis.clients.jedis.exceptions.JedisConnectionException: All sentinels down, cannot determine where is mymaster master is running...
    at redis.clients.jedis.JedisSentinelPool.initSentinels(JedisSentinelPool.java:180)
    at redis.clients.jedis.JedisSentinelPool.<init>(JedisSentinelPool.java:95)
    at redis.clients.jedis.JedisSentinelPool.<init>(JedisSentinelPool.java:82)
    at redis.clients.jedis.JedisSentinelPool.<init>(JedisSentinelPool.java:70)
    at redis.clients.jedis.JedisSentinelPool.<init>(JedisSentinelPool.java:44)
    at RedisPush.pushToRedis(RedisPush.java:29)
    at RedisPush.main(RedisPush.java:61)

However, if I change my sentinel configuration script to the one below:

# bind 127.0.0.1
port 5000
protected-mode no
sentinel monitor mymaster 127.0.0.1 6379 2
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 60000
sentinel auth-pass mymaster foobared

the client works perfectly. I don't understand why.

AFAIK, if requirepass is not set in sentinel.conf file AND bind is commented in sentinel.conf file, ONLY then protected-mode will be yes to avoid any client connecting to the sentinel apart from localhost. In my first sentinel configuration, I had the bind command but still it didn't work.

Why does commenting out bind and explicitly setting protected-mode to no works?

P.S. I also tried having both bind 127.0.0.1 and protected-mode no but even that didn't work.

Answer 1

Jedis doesn't support well Redis Sentinel. Use Lettuce instead which has a better pool management. And well supported on springboot too.

Answer 2

I had a similar issue where Jedis was throwing the same error, it was related to https://github.com/xetorthio/jedis/issues/1367

To get around this on my mac I did sudo ifconfig lo0 alias 127.0.1.1 Then changed my sentinel.conf to bind 127.0.1.1 and then updated my yaml for spring data to connect to that ip

sentinel.nodes: 127.0.1.1:5000, 127.0.1.1:5002, 127.0.1.1:5003