What are the solutions for redis distributed ID?

Commonly used distributed ID solutions

In a distributed system, it is very important to generate a globally unique ID, because in a distributed system, Multiple nodes generating IDs at the same time may cause ID conflicts.

The following introduces several commonly used distributed ID solutions.

UUID

UUID (Universally Unique Identifier) ​​is an identifier composed of 128 digits, which can guarantee global uniqueness because its generation algorithm is based on timestamps, nodes ID and other factors. UUID can be generated using Java's own UUID class, as shown below:

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import java.util.UUID;
public class UuidGenerator {
    public static void main(String[] args) {
        UUID uuid = UUID.randomUUID();
        System.out.println(uuid.toString());
    }
}

The UUID generated by Java's own UUID class is very simple and easy to use, and does not require additional configuration and management. This is its advantage. Due to its length (128 bits), UUID is not suitable as a primary key for database tables and is difficult to sort and index.

Snowflake

Snowflake is a distributed ID generation algorithm open sourced by Twitter. It can generate a 64-bit unique ID, which contains information such as timestamp, data center ID, and machine ID. The Java code of the Snowflake algorithm is as follows:

The Java code of the Snowflake algorithm:

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public class SnowflakeGenerator {
    private final static long START_STMP = 1480166465631L;
    private final static long SEQUENCE_BIT = 12;
    private final static long MACHINE_BIT = 5;
    private final static long DATACENTER_BIT = 5;
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
    private long datacenterId;
    private long machineId;
    private long sequence = 0L;
    private long lastStmp = -1L;
    public SnowflakeGenerator(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can&#39;t be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can&#39;t be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }
    public synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }
        if (currStmp == lastStmp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            sequence = 0L;
        }
        lastStmp = currStmp;
        return (currStmp - START_STMP) << TIMESTMP_LEFT
                | datacenterId << DATACENTER_LEFT
                | machineId << MACHINE_LEFT
                | sequence;
    }
    private long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }
    private long getNewstmp() {
        return System.currentTimeMillis();
    }
}

The advantages of the Snowflake algorithm are high performance in generating IDs and short ID length (64 bits), which can As the primary key of the database table, it facilitates sorting and indexing. However, it should be noted that if the number of nodes in the cluster exceeds the number of digits occupied by the machine ID, or the cluster is very large and the number of timestamp digits is not enough, then other distributed ID generation algorithms need to be considered.

Leaf

Leaf is a distributed ID generation algorithm open sourced by Meituan Dianping. It can generate a globally unique 64-bit ID. The Java code of the Leaf algorithm is as follows:

The Java code of the Leaf algorithm:

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public class LeafGenerator {
    private static final Logger logger = LoggerFactory.getLogger(LeafGenerator.class);
    private static final String WORKER_ID_KEY = "leaf.worker.id";
    private static final String PORT_KEY = "leaf.port";
    private static final int DEFAULT_PORT = 8080;
    private static final int DEFAULT_WORKER_ID = 0;
    private static final int WORKER_ID_BITS = 10;
    private static final int SEQUENCE_BITS = 12;
    private static final int MAX_WORKER_ID = (1 << WORKER_ID_BITS) - 1;
    private static final int MAX_SEQUENCE = (1 << SEQUENCE_BITS) - 1;
    private static final long EPOCH = 1514736000000L;
    private final SnowflakeIdWorker idWorker;
    public LeafGenerator() {
        int workerId = SystemPropertyUtil.getInt(WORKER_ID_KEY, DEFAULT_WORKER_ID);
        int port = SystemPropertyUtil.getInt(PORT_KEY, DEFAULT_PORT);
        this.idWorker = new SnowflakeIdWorker(workerId, port);
        logger.info("Initialized LeafGenerator with workerId={}, port={}", workerId, port);
    }
    public long nextId() {
        return idWorker.nextId();
    }
    private static class SnowflakeIdWorker {
        private final long workerId;
        private final long port;
        private long sequence = 0L;
        private long lastTimestamp = -1L;
        SnowflakeIdWorker(long workerId, long port) {
            if (workerId < 0 || workerId > MAX_WORKER_ID) {
                throw new IllegalArgumentException(String.format("workerId must be between %d and %d", 0, MAX_WORKER_ID));
            }
            this.workerId = workerId;
            this.port = port;
        }
        synchronized long nextId() {
            long timestamp = System.currentTimeMillis();
            if (timestamp < lastTimestamp) {
                throw new RuntimeException("Clock moved backwards. Refusing to generate id");
            }
            if (timestamp == lastTimestamp) {
                sequence = (sequence + 1) & MAX_SEQUENCE;
                if (sequence == 0L) {
                    timestamp = tilNextMillis(lastTimestamp);
                }
            } else {
                sequence = 0L;
            }
            lastTimestamp = timestamp;
            return ((timestamp - EPOCH) << (WORKER_ID_BITS + SEQUENCE_BITS))
                    | (workerId << SEQUENCE_BITS)
                    | sequence;
        }
        private long tilNextMillis(long lastTimestamp) {
            long timestamp = System.currentTimeMillis();
            while (timestamp <= lastTimestamp) {
                timestamp = System.currentTimeMillis();
            }
            return timestamp;
        }
    }
}

Although the Leaf algorithm generates IDs slightly slower than the Snowflake algorithm, it can support more worker nodes . The ID generated by the Leaf algorithm consists of three parts, namely timestamp, Worker ID and sequence number. The timestamp occupies 42 bits, the Worker ID occupies 10 bits, and the sequence number occupies 12 bits, for a total of 64 bits.

The above are common distributed ID generation algorithms. Of course, there are other solutions, such as: MongoDB ID, UUID, Twitter Snowflake, etc. Different solutions are suitable for different business scenarios, and the specific implementation details and performance are also different. You need to choose the appropriate solution based on the actual situation.

In addition to the distributed ID generation algorithm introduced above, there are also some new distributed ID generation solutions emerging, such as Flicker's distributed ID generation algorithm, which uses ideas similar to Snowflake, but adopts Different bit allocation methods are more flexible than Snowflake, and the number of bits occupied by each part can be dynamically adjusted as needed. In addition, Facebook also launched the ID Generation Service (IGS) solution, which separates ID generation and storage, providing a more flexible and scalable solution, but requires more complex architecture design and implementation.

According to different business needs, multiple sets of distributed ID generation solutions can be designed. Here are some of my personal suggestions:

• Generate based on database auto-increment ID: Using database auto-increment ID as a globally unique ID can ensure the uniqueness of the ID and is simple to implement. , but high concurrency may cause performance bottlenecks. Therefore, it is not recommended to use it in high concurrency scenarios.

• Generate based on UUID: Using UUID as a globally unique ID can ensure the uniqueness of the ID, but the ID length is long (128 bits), which is not convenient for storage and transmission, and The probability of duplicate IDs is very small but not 0. It is recommended that when using a distributed system, the ID length and the cost of storage and transmission need to be considered.

• Generation based on Redis: Using the atomic operation of Redis can ensure the uniqueness of the ID, and the ID generation speed is very fast, which can be applied to high concurrency scenarios. It should be noted that if Redis crashes or performs poorly, it may affect ID generation efficiency and availability.

• Generation based on ZooKeeper: Using ZooKeeper's serial number generator can ensure the uniqueness of the ID, and the implementation is relatively simple, but it requires the introduction of additional dependencies and resources, and there may be performance issues bottleneck.

To choose a distributed ID generation solution that suits your business scenario, you need to comprehensively consider multiple factors such as ID uniqueness, generation speed, length, storage cost, scalability, and availability. Implementing different solutions requires consideration of trade-offs and choices in actual situations, because their implementation details and performance are also different.

The detailed code demo of each solution is given below:

Generate based on database auto-increment ID

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public class IdGenerator {
    private static final String JDBC_URL = "jdbc:mysql://localhost:3306/test";
    private static final String JDBC_USER = "root";
    private static final String JDBC_PASSWORD = "password";
    public long generateId() {
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(JDBC_URL, JDBC_USER, JDBC_PASSWORD);
            pstmt = conn.prepareStatement("INSERT INTO id_generator (stub) VALUES (null)", Statement.RETURN_GENERATED_KEYS);
            pstmt.executeUpdate();
            rs = pstmt.getGeneratedKeys();
            if (rs.next()) {
                return rs.getLong(1);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                }
                if (pstmt != null) {
                    pstmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return 0L;
    }
}

Generate based on UUID

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import java.util.UUID;
public class IdGenerator {
    public String generateId() {
        return UUID.randomUUID().toString().replace("-", "");
    }
}

Generate based on Redis

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import redis.clients.jedis.Jedis;
public class IdGenerator {
    private static final String REDIS_HOST = "localhost";
    private static final int REDIS_PORT = 6379;
    private static final String REDIS_PASSWORD = "password";
    private static final int ID_GENERATOR_EXPIRE_SECONDS = 3600;
    private static final String ID_GENERATOR_KEY = "id_generator";
    public long generateId() {
        Jedis jedis = null;
        try {
            jedis = new Jedis(REDIS_HOST, REDIS_PORT);
            jedis.auth(REDIS_PASSWORD);
            long id = jedis.incr(ID_GENERATOR_KEY);
            jedis.expire(ID_GENERATOR_KEY, ID_GENERATOR_EXPIRE_SECONDS);
            return id;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
        return 0L;
    }
}

Generated based on ZooKeeper

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import java.util.concurrent.CountDownLatch;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
public class IdGenerator implements Watcher {
    private static final String ZK_HOST = "localhost";
    private static final int ZK_PORT = 2181;
    private static final int SESSION_TIMEOUT = 5000;
    private static final String ID_GENERATOR_NODE = "/id_generator";
    private static final int ID_GENERATOR_EXPIRE_SECONDS = 3600;
    private long workerId = 0;
    public IdGenerator() {
        try {
            ZooKeeper zk = new ZooKeeper(ZK_HOST + ":" + ZK_PORT, SESSION_TIMEOUT, this);
            CountDownLatch latch = new CountDownLatch(1);
            latch.await();
            if (zk.exists(ID_GENERATOR_NODE, false) == null) {
                zk.create(ID_GENERATOR_NODE, null, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
            workerId = zk.getChildren(ID_GENERATOR_NODE, false).size();
            zk.create(ID_GENERATOR_NODE + "/worker_" + workerId, null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public long generateId() {
        ZooKeeper zk = null;
        try {
            zk = new ZooKeeper(ZK_HOST + ":" + ZK_PORT, SESSION_TIMEOUT, null);
            CountDownLatch latch = new CountDownLatch(1);
            latch.await();
            zk.create(ID_GENERATOR_NODE + "/id_", null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL, (rc, path, ctx, name) -> {}, null);
            byte[] data = zk.getData(ID_GENERATOR_NODE + "/worker_" + workerId, false, null);
            long id = Long.parseLong(new String(data)) * 10000 + zk.getChildren(ID_GENERATOR_NODE, false).size();
            return id;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (zk != null) {
                try {
                    zk.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
        return 0L;
    }
    @Override
    public void process(WatchedEvent event) {
        if (event.getState() == Event.KeeperState.SyncConnected) {
            System.out.println("Connected to ZooKeeper");
            CountDownLatch latch = new CountDownLatch(1);
            latch.countDown();
        }
    }
}

Note that ZooKeeper's temporary nodes are used here to coordinate each working node. If a working node hangs up, its temporary node will also be deleted, so that Ensure that the ID obtained by each worker node is unique.

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