Redis客户端连接方式Hiredis简单封装使用,连接池、屏蔽连接细节

工作需要对Hiredis进行了简单封装，实现功能：

1、API进行统一，对外只提供一个接口；

2、屏蔽上层应用对连接的细节处理；

3、底层采用队列的方式保持连接池，保存连接会话；

4、重连时采用时间戳进行控制，每隔一定时间(3s)重连一次，防止频繁重试造成的不必要浪费。

先看一下Hiredis的常用数据结构与API：

//hiredis/hiredis.h
/* Context for a connection to Redis */
typedef struct redisContext {
    int err; /* Error flags, 0 when there is no error */
    char errstr[128]; /* String representation of error when applicable */
    int fd;
    int flags;
    char *obuf; /* Write buffer */
    redisReader *reader; /* Protocol reader */
} redisContext;

/* This is the reply object returned by redisCommand() */
#define REDIS_REPLY_STRING 1
#define REDIS_REPLY_ARRAY 2
#define REDIS_REPLY_INTEGER 3
#define REDIS_REPLY_NIL 4
#define REDIS_REPLY_STATUS 5
#define REDIS_REPLY_ERROR 6
typedef struct redisReply {
    int type; /* REDIS_REPLY_* */
    long long integer; /* The integer when type is REDIS_REPLY_INTEGER */
    int len; /* Length of string */
    char *str; /* Used for both REDIS_REPLY_ERROR and REDIS_REPLY_STRING */
    size_t elements; /* number of elements, for REDIS_REPLY_ARRAY */
    struct redisReply **element; /* elements vector for REDIS_REPLY_ARRAY */
} redisReply;

redisContext *redisConnectWithTimeout(const char *ip, int port, struct timeval tv);
void redisFree(redisContext *c);
//Issue a command to Redis, NULL if error, otherwise reply
void *redisCommand(redisContext *c, const char *format, ...);
/* Function to free the reply objects hiredis returns by default. */
void freeReplyObject(void *reply);

下面直接上封装后的代码：

class KGRedisClient
{
public:
    KGRedisClient(string ip, int port, int timeout = 2000);
    virtual ~KGRedisClient();

    bool ExecuteCmd(const char *cmd, string &response);
    redisReply* ExecuteCmd(const char *cmd);

private:
    int m_timeout;
    int m_serverPort;
    string m_setverIp;
    CCriticalSection m_lock;
    std::queue<redisContext *> m_clients;

    time_t m_beginInvalidTime;
    static const int m_maxReconnectInterval = 3;

    redisContext* CreateContext();
    void ReleaseContext(redisContext *ctx, bool active);
    bool CheckStatus(redisContext *ctx);
};

KGRedisClient::KGRedisClient(string ip, int port, int timeout)
{
    m_timeout = timeout;
    m_serverPort = port;
    m_setverIp = ip;

    m_beginInvalidTime = 0;
}

KGRedisClient::~KGRedisClient()
{
    CAutoLock autolock(m_lock);
    while(!m_clients.empty())
    {
        redisContext *ctx = m_clients.front();
        redisFree(ctx);
        m_clients.pop();
    }
}

bool KGRedisClient::ExecuteCmd(const char *cmd, string &response)
{
    redisReply *reply = ExecuteCmd(cmd);
    if(reply == NULL) return false;

    boost::shared_ptr<redisReply> autoFree(reply, freeReplyObject);
    if(reply->type == REDIS_REPLY_INTEGER)
    {
        response = _IntToStrA(reply->integer);
        return true;
    }
    else if(reply->type == REDIS_REPLY_STRING)
    {
        response.assign(reply->str, reply->len);
        return true;
    }
    else if(reply->type == REDIS_REPLY_STATUS)
    {
        response.assign(reply->str, reply->len);
        return true;
    }
    else if(reply->type == REDIS_REPLY_NIL)
    {
        response = "";
        return true;
    }
    else if(reply->type == REDIS_REPLY_ERROR)
    {
        response.assign(reply->str, reply->len);
        return false;
    }
    else if(reply->type == REDIS_REPLY_ARRAY)
    {
        response = "Not Support Array Result!!!";
        return false;
    }
    else
    {
        response = "Undefine Reply Type";
        return false;
    }
}

redisReply* KGRedisClient::ExecuteCmd(const char *cmd)
{
    redisContext *ctx = CreateContext();
    if(ctx == NULL) return NULL;

    redisReply *reply = (redisReply*)redisCommand(ctx, cmd);

    ReleaseContext(ctx, reply != NULL);

    return reply;
}

redisContext* KGRedisClient::CreateContext()
{
    {
        CAutoLock autolock(m_lock);
        if(!m_clients.empty())
        {
            redisContext *ctx = m_clients.front();
            m_clients.pop();

            return ctx;
        }
    }

    time_t now = time(NULL);
    if(now < m_beginInvalidTime + m_maxReconnectInterval) return NULL;

    struct timeval tv;
    tv.tv_sec = m_timeout / 1000;
    tv.tv_usec = (m_timeout % 1000) * 1000;;
    redisContext *ctx = redisConnectWithTimeout(m_setverIp.c_str(), m_serverPort, tv);
    if(ctx == NULL || ctx->err != 0)
    {
        if(ctx != NULL) redisFree(ctx);

        m_beginInvalidTime = time(NULL);

        return NULL;
    }

    return ctx;
}

void KGRedisClient::ReleaseContext(redisContext *ctx, bool active)
{
    if(ctx == NULL) return;
    if(!active) {redisFree(ctx); return;}

    CAutoLock autolock(m_lock);
    m_clients.push(ctx);
}

bool KGRedisClient::CheckStatus(redisContext *ctx)
{
    redisReply *reply = (redisReply*)redisCommand(ctx, "ping");
    if(reply == NULL) return false;

    boost::shared_ptr<redisReply> autoFree(reply, freeReplyObject);

    if(reply->type != REDIS_REPLY_STATUS) return false;
    if(strcasecmp(reply->str,"PONG") != 0) return false;

    return true;
}

稍加解释：

成员变量：m_clients用于保存连接池。

成员变量：m_beginInvalidTime、m_maxReconnectInterval 用于控制断掉时的频繁连接。

对外API：ExecuteCmd(const char *cmd, string &response);