flink 利用 redis 去重

flink 利用 redis 去重

对于每一条待处理的 record，根据算法计算其唯一key：

    key = getMessageKey(record);

如果 key 不存在，设置key值=0和超时. redis 保证 setnx 指令是原子的：

    result = cmds.set(key, "0", nxShortTimeArgs);

如果 key 存在, result 返回 nil。如果返回 OK 说明线程获得了key，继续操作：

    onCollectKey(key, value, out);

上面的过程记录下来，就是下面这个类，使用时需要继承并实现几个重载函数：

/**
 * RedisStatefulMapFunction.java
 *
 *   https://ci.apache.org/projects/flink/flink-docs-master/api/java/org/apache/flink/api/common/functions/RichFlatMapFunction.html
 *   https://ci.apache.org/projects/flink/flink-docs-master/api/java/org/apache/flink/api/common/typeinfo/TypeHint.html

 *
 *
 * create: 2020-11-19
 * update: 2020-12-15
 */
package com.cheungmine.flink.common;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.pepstack.guru.LogUtil;
import com.pepstack.guru.RedisClusterIO;

import java.time.Duration;
import java.util.Properties;

import org.apache.flink.api.common.functions.RichFlatMapFunction;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.util.Collector;

import io.lettuce.core.cluster.RedisClusterClient;
import io.lettuce.core.cluster.api.StatefulRedisClusterConnection;
import io.lettuce.core.cluster.api.sync.RedisAdvancedClusterCommands;
import io.lettuce.core.SetArgs;


public class RedisStatefulMapFunction<IN, OUT> extends RichFlatMapFunction<IN, OUT> {
    private static final Logger logger = LoggerFactory.getLogger(RedisStatefulMapFunction.class);

    private transient RedisClusterClient redisClient;
    private transient StatefulRedisClusterConnection<String, String> connection;

    private static final String[] propKeys = new String[] {
        "redis.cluser.uris"
        ,"redis.timeout.millis"
        ,"redis.expire.seconds"
    };

    private final String[] redisClusterUris;

    private final int redisTimeoutMillis;
    private final long redisExpireSeconds;

    private final SetArgs nxShortTimeArgs;
    private final SetArgs xxExpireTimeArgs;


    protected RedisStatefulMapFunction(Properties kvprops) throws Exception {
        // hard code here:
        redisClusterUris = new String[] {
            "redis://[email protected]:7001?timeout=30s",
            "redis://[email protected]:7002?timeout=30s",
            "redis://[email protected]:7003?timeout=30s",
            "redis://[email protected]:7004?timeout=30s",
            "redis://[email protected]:7005?timeout=30s",
            "redis://[email protected]:7006?timeout=30s",
            "redis://[email protected]:7007?timeout=30s",
            "redis://[email protected]:7008?timeout=30s",
            "redis://[email protected]:7009?timeout=30s"
        };

        redisTimeoutMillis = 30*1000;
        redisExpireSeconds = 86400*30;

        nxShortTimeArgs = SetArgs.Builder.nx().px(redisTimeoutMillis);
        xxExpireTimeArgs = SetArgs.Builder.xx().ex(redisExpireSeconds);
    }

    // 子类必须覆盖此方法
    public String getMessageKey(IN value)
    {
        // 根据 IN value 记录计算其签名值 (签名值一样的记录被任务是重复记录)
        // 子类应该实现这个方法, 返回 null 值表面放弃本消息
        return null;
    }


    // 子类必须覆盖此方法
    public void onCollectKey (String key, IN value, Collector<OUT> out)
    {
        LogUtil.debug(logger, "{%s}", key);
    }


    // 子类最好忽略此方法
    public void onDiscardKey (String key, IN value, Collector<OUT> out)
    {
        // 其他线程已经处理了这个消息
        LogUtil.warn(logger, "{%s}", key);
    }


    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);

        redisClient = RedisClusterIO.createClient(redisClusterUris, Duration.ofMillis(redisTimeoutMillis));
        connection = redisClient.connect();
    }


    @Override
    public void close() throws Exception {
        super.close();

        connection.close();
        RedisClusterIO.shutdownClient(redisClient);
    }


    @Override
    public void flatMap(IN value, Collector<OUT> out) throws Exception {
        RedisAdvancedClusterCommands<String, String> cmds = connection.sync();

        // 根据 IN value 记录计算其签名值 key
        final String key = getMessageKey(value);

        if (key != null) {
            // redis 保证 setnx 指令是原子的, 仅仅当 key 不存在设置其值和过期时间
            final String result = cmds.set(key, "0", nxShortTimeArgs);

            if (result != null && result.equals("OK")) {
                // 处理该记录
                onCollectKey(key, value, out);

                // 至此被任务记录操作成功, 设置一个较长的过期时间.
                // redis 保证 setxx 指令是原子的, 仅当 key 存在设置其值和过期时间
                cmds.set(key, "1", xxExpireTimeArgs);
            } else {
                // 忽略该记录
                onDiscardKey(key, value, out);
            }
        }
    }
}

redis 集群操作类 RedisClusterIO：

/**
 * RedisClusterIO.java
 *  操作 Redis 集群
 *
 */
package com.pepstack.guru;

import com.pepstack.guru.LogUtil;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.Iterator;
import java.util.Map.Entry;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import java.time.Duration;

import io.lettuce.core.RedisClient;
import io.lettuce.core.RedisFuture;
import io.lettuce.core.RedisURI;
import io.lettuce.core.api.StatefulRedisConnection;
import io.lettuce.core.api.sync.RedisStringCommands;
import io.lettuce.core.api.async.RedisStringAsyncCommands;

// https://github.com/lettuce-io/lettuce-core/blob/6.0.1.RELEASE/src/test/java/io/lettuce/examples/ConnectToRedisCluster.java
import io.lettuce.core.cluster.RedisClusterClient;
import io.lettuce.core.cluster.api.StatefulRedisClusterConnection;


public class RedisClusterIO {
    private static final Logger logger = LoggerFactory.getLogger(RedisClusterIO.class);

    private RedisClusterIO() {
    }


    public static RedisClusterClient createClient(String[] uris, Duration defaultTimeout) throws Exception {
        RedisClusterClient redisClient = null;

        List<RedisURI> list = new ArrayList<RedisURI>();
        for (int i = 0; i < uris.length; i++) {
            // uri Syntax:
            //   redis://[password@]host[:port][/databaseNumber][?[timeout=timeout[d|h|m|s|ms|us|ns]]
            LogUtil.info(logger, String.format("redis-server.%d=%s", i+1, uris[i]));

            list.add(RedisURI.create(uris[i]));
        }

        redisClient = RedisClusterClient.create(list);

        if (defaultTimeout != null) {
            redisClient.setDefaultTimeout(defaultTimeout);
        }

        return redisClient;
    }


    public static RedisClusterClient createClient(Properties props) throws Exception {
        int maxid = 0;
        while (props.getProperty(String.format("redis-server.%d", maxid+1), null) != null) {
            maxid++;
        }

        final String[] uris = new String[maxid];
        for (int i = 0; i < maxid; i++) {
            uris[i] = props.getProperty(String.format("redis-server.%d", i + 1));
        }
        return createClient(uris, null);
    }


    public static void shutdownClient(RedisClusterClient client) throws Exception {
        client.shutdown();
    }
}

特此记录。