Redis实战之多用户聊天室

多客户端之间的通信，可采用消息推送和消息拉取两种方法。所谓消息推送，即采用publish/subscribe模式，但该方法要求用户必须在线才能接收到消息；所谓消息拉取模式，即由接收端自己拉取存储在某种邮箱里的消息。

数据结构

1、群

群ID计数器：（string）

ids:chat

群成员：（zset，包括群内所有成员及其拉取的最新消息ID）

chat:群ID Last_Message_ID 用户ID

消息ID计数器：（string）

ids:msg:群ID

群消息：（zset）

msgs:群ID 消息ID 消息内容

2、用户

群组：（zset，包括用户加入的群及从群内拉取的最新消息ID）

seen:用户ID Last_Message_ID 群ID

原理

1、建群

incr ids:chat

2、进群

2.1、获取最新群消息ID：

Current_Message_ID = get ids:msg:群ID

2.2、修改群成员集合，更新用户从群内拉取的最新消息ID：

zadd chat:群ID Current_Message_ID 用户ID

2.3、修改用户加入的群，更新用户从群内拉取的最新消息ID：

zadd seen:用户ID Current_Message_ID 群ID

3、退群

3.1、修改群成员集合：

zrem chat:群ID 用户ID

3.2、修改用户加入的群：

zrem seen:用户ID 群ID

3.3、清除群消息：
1）获取群成员集合中剩余成员数目：

Number = zcard chat:群ID
2）若 Number <= 0，则删除群消息ID计数器和群内所有消息：
del ids:msg:群ID
zremrangebyrank msgs:群ID 0 -1
3）若 Number > 0，则：
获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取：
Min_Score = zrange chat:群ID 0 0 withscores
清除已被所有成员拉取的消息：
zremrangebyscore msgs:群ID 0 Min_Score

4、发送消息

4.1、创建群消息ID：

New_Message_ID = incr ids:msg:群ID

4.2、将消息添加到群消息集合：

zadd msgs:群ID New_Message_ID 消息内容

5、拉取消息

5.1、获取用户所加入的群信息（包括群ID和从群内最后拉取的消息ID）：

<群ID, Last_Message_ID> = zrange seen:用户ID 0 -1 withscores

5.2、遍历所加入的群，拉取所有群消息（并记录最大未读群消息ID：Max_Message_ID）：

zrangebyscore msgs:群ID Last_Message_ID+1 inf

5.3、修改群成员集合和用户加入群集合，更新用户从群内拉取的最大消息ID：

zadd chat:群ID Max_Message_ID 用户ID
zadd seen:用户ID Max_Message_ID 群ID

5.4、清除已被所有成员拉取的消息：
获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取：

Min_Score = zrange chat:群ID 0 0 withscores
清除已被所有人阅读的消息：
zremrangebyscore msgs:群ID -inf Min_Score

实现

1、建群

int ChatManager::createChat(){    // 分配群ID    redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "INCR ids:chat");    if (pRedisReply == NULL)    {        return -1;    }    int nChatID = pRedisReply->integer;    freeReplyObject(pRedisReply);    return nChatID;}

2、进群

bool ChatManager::joinChat(int nChatID, QString &strUser){    //1、获取最新群消息ID    QString strMsgIDKeyName = QString("ids:msg:%1").arg(nChatID);    redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "GET %s", strMsgIDKeyName.toLocal8Bit().data());    if (pRedisReply == NULL)    {        return false;    }    int nLastMsgID = pRedisReply->integer;    freeReplyObject(pRedisReply);    //2、修改群成员集合，更新用户从群内拉取的最新消息ID    QString strChatKeyName = QString("chat:%1").arg(nChatID);    pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %s", strChatKeyName.toLocal8Bit().data(), nLastMsgID, strUser.toLocal8Bit().data());    if (pRedisReply == NULL)    {        return false;    }    freeReplyObject(pRedisReply);    //3、修改用户加入的群，更新用户从群内拉取的最新消息ID    QString strSeenKeyName = QString("seen:%1").arg(strUser);    pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %d", strSeenKeyName.toLocal8Bit().data(), nLastMsgID, nChatID);    if (pRedisReply == NULL)    {        return false;    }    freeReplyObject(pRedisReply);    return true;}

3、退群

bool ChatManager::leaveChat(int nChatID, QString &strUser){    //1、修改群成员集合    QString strChatKeyName = QString("chat:%1").arg(nChatID);    redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREM %s %s", strChatKeyName.toLocal8Bit().data(), strUser.toLocal8Bit().data());    if (pRedisReply == NULL)    {        return false;    }    freeReplyObject(pRedisReply);    //2、修改用户加入的群    QString strSeenKeyName = QString("seen:%1").arg(strUser);    pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREM %s %d", strSeenKeyName.toLocal8Bit().data(), nChatID);    if (pRedisReply == NULL)    {        return false;    }    freeReplyObject(pRedisReply);    //清除群消息    //3、获取群成员集合中剩余成员数目    pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZCARD %s", strChatKeyName.toLocal8Bit().data());    if (pRedisReply == NULL)    {        return false;    }    int nMembers = pRedisReply->integer;    freeReplyObject(pRedisReply);    if (nMembers <= 0)    {        //群内无剩余成员        //4、删除群消息ID计数器        QString strMsgIDKeyName = QString("ids:msg:%1").arg(nChatID);        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "DEL %s", strMsgIDKeyName.toLocal8Bit().data());        if (pRedisReply == NULL)        {            return false;        }        freeReplyObject(pRedisReply);        //5、删除群内所有消息        QString strMsgKeyName = QString("msg:%1").arg(nChatID);        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREMRANGEBYRANK %s 0 -1", strMsgKeyName.toLocal8Bit().data());        if (pRedisReply == NULL)        {            return false;        }        freeReplyObject(pRedisReply);    }    else    {        //群内还有剩余成员 清除已被所有成员拉取的消息        //6、获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGE %s 0 0 WITHSCORES", strChatKeyName.toLocal8Bit().data());        if (pRedisReply == NULL)        {            return false;        }        int nScore = atoi(pRedisReply->element[1]->str);        freeReplyObject(pRedisReply);        //7、清除已被所有成员拉取的消息        QString strMsgKeyName = QString("msg:%1").arg(nChatID);        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREMRANGEBYSCORE %s 0 %d", strMsgKeyName.toLocal8Bit().data(), nScore);        if (pRedisReply == NULL)        {            return false;        }        freeReplyObject(pRedisReply);    }    return true;}

4、发送消息

bool ChatManager::sendMsg(int nChatID, QString &strMsgInfo){    //1、创建群消息ID    QString strMsgIDKeyName = QString("ids:msg:%1").arg(nChatID);    redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "INCR %s", strMsgIDKeyName.toLocal8Bit().data());    if (pRedisReply == NULL)    {        return false;    }    int nNewMsgID = pRedisReply->integer;    freeReplyObject(pRedisReply);    //2、将消息添加到群消息集合    QString strMsgKeyName = QString("msg:%1").arg(nChatID);    pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %s", strMsgKeyName.toLocal8Bit().data(), nNewMsgID, strMsgInfo.toLocal8Bit().data());    if (pRedisReply == NULL)    {        return false;    }    freeReplyObject(pRedisReply);    return true;}

5、拉取消息

bool ChatManager::fetchMsg(QString &strUser){    //1、获取用户所加入的群信息（包括群ID和从群内最后拉取的消息ID）    QString strSeenKeyName = QString("seen:%1").arg(strUser);    redisReply *pSeenRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGE %s 0 -1 WITHSCORES", strSeenKeyName.toLocal8Bit().data());    if (pSeenRedisReply == NULL)    {        return false;    }    //2、遍历所加入的群    for (int nIndex = 0; nIndex < pSeenRedisReply->elements; nIndex = nIndex + 2)    {        int nChatID = atoi(pSeenRedisReply->element[nIndex]->str);        int nNextLastMsgID = atoi(pSeenRedisReply->element[nIndex + 1]->str) + 1;        //3、拉取所有群消息        QString strMsgKeyName = QString("msg:%1").arg(nChatID);        redisReply *pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGEBYSCORE %s %d INF WITHSCORES", strMsgKeyName.toLocal8Bit().data(), nNextLastMsgID);        if (pRedisReply == NULL)        {            freeReplyObject(pSeenRedisReply);            return false;        }        if (0 == pRedisReply->elements)        {            continue;   //没有未读消息        }        //4、展示所有未读消息        int nMaxMsgID = 0;        for (int nMsgIndex = 0; nMsgIndex < pRedisReply->elements; nMsgIndex = nMsgIndex + 2)        {            QString strMsgInfo = pRedisReply->element[nMsgIndex]->str;            int nMsgID = atoi(pRedisReply->element[nMsgIndex + 1]->str);            // 展示消息            if (nMsgID > nMaxMsgID)            {                nMaxMsgID = nMsgID;            }        }        freeReplyObject(pRedisReply);        //5、修改群成员集合 更新用户从群内拉取的最大消息ID        QString strChatKeyName = QString("chat:%1").arg(nChatID);        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %s", strChatKeyName.toLocal8Bit().data(), nMaxMsgID, strUser.toLocal8Bit().data());        if (pRedisReply == NULL)        {            freeReplyObject(pSeenRedisReply);            return false;        }        freeReplyObject(pRedisReply);        //6、修改用户加入群集合 更新用户从群内拉取的最大消息ID        QString strSeenKeyName = QString("seen:%1").arg(strUser);        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZADD %s %d %d", strSeenKeyName.toLocal8Bit().data(), nMaxMsgID, nChatID);        if (pRedisReply == NULL)        {            freeReplyObject(pSeenRedisReply);            return false;        }        freeReplyObject(pRedisReply);        //清除已被所有成员拉取的消息        //7、获取群成员集合中最小的score，最小score之前的消息必定已被所有用户拉取        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZRANGE %s 0 0 WITHSCORES", strChatKeyName.toLocal8Bit().data());        if (pRedisReply == NULL)        {            freeReplyObject(pSeenRedisReply);            return false;        }        if (pRedisReply->elements != 2)        {            continue;        }        int nOldMsgID = atoi(pRedisReply->element[1]->str);        freeReplyObject(pRedisReply);        //8、清除已被所有人阅读的消息        pRedisReply = (redisReply *)redisCommand(m_pRedisContext, "ZREMRANGEBYSCORE %s -INF %d", strMsgKeyName.toLocal8Bit().data(), nOldMsgID);        if (pRedisReply == NULL)        {            freeReplyObject(pSeenRedisReply);            return false;        }        freeReplyObject(pRedisReply);    }    freeReplyObject(pSeenRedisReply);    return true;}