redis网络接口封装

网络相关的位于文件anet.c/anet.h文件中。

接口定义

//tcp连接
int anetTcpConnect(char *err, char *addr, int port);
//设置非阻塞
int anetTcpNonBlockConnect(char *err, char *addr, int port);
//unix本地套接字连接
int anetUnixConnect(char *err, char *path);
//非阻塞
int anetUnixNonBlockConnect(char *err, char *path);
//读
int anetRead(int fd, char *buf, int count);
//地址转换
int anetResolve(char *err, char *host, char *ipbuf, size_t ipbuf_len);
int anetResolveIP(char *err, char *host, char *ipbuf, size_t ipbuf_len);
//tcp server
int anetTcpServer(char *err, int port, char *bindaddr, int backlog);
int anetTcp6Server(char *err, int port, char *bindaddr, int backlog);
//本地套接字server
int anetUnixServer(char *err, char *path, mode_t perm, int backlog);
//tcp等待连接
int anetTcpAccept(char *err, int serversock, char *ip, size_t ip_len, int *port);
//本地套接字等待连接
int anetUnixAccept(char *err, int serversock);
//写
int anetWrite(int fd, char *buf, int count);
//设置非阻塞
int anetNonBlock(char *err, int fd);
//关闭tcp的delay发送策略
int anetEnableTcpNoDelay(char *err, int fd);
//开启delay发送策略
int anetDisableTcpNoDelay(char *err, int fd);
//开启保活
int anetTcpKeepAlive(char *err, int fd);
//获取对端的ip:port
int anetPeerToString(int fd, char *ip, size_t ip_len, int *port);
//设置保活
int anetKeepAlive(char *err, int fd, int interval);
//获取本端的ip:port
int anetSockName(int fd, char *ip, size_t ip_len, int *port);

保活机制

int anetKeepAlive(char *err, int fd, int interval)
{
    int val = 1;
    //激活keepalive功能
    if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof(val)) == -1)
    {
        anetSetError(err, "setsockopt SO_KEEPALIVE: %s", strerror(errno));
        return ANET_ERR;
    }

#ifdef __linux__
    /* Default settings are more or less garbage, with the keepalive time
     * set to 7200 by default on Linux. Modify settings to make the feature
     * actually useful. */

    /* Send first probe after interval. */
    val = interval;
    //在interval 秒没有数据后，发送keepalive
    if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &val, sizeof(val)) < 0) {
        anetSetError(err, "setsockopt TCP_KEEPIDLE: %s\n", strerror(errno));
        return ANET_ERR;
    }

    /* Send next probes after the specified interval. Note that we set the
     * delay as interval / 3, as we send three probes before detecting
     * an error (see the next setsockopt call). */
    val = interval/3;
    if (val == 0) val = 1;
    //发送keepalive的间隔为interval/3
    if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL, &val, sizeof(val)) < 0) {
        anetSetError(err, "setsockopt TCP_KEEPINTVL: %s\n", strerror(errno));
        return ANET_ERR;
    }

    /* Consider the socket in error state after three we send three ACK
     * probes without getting a reply. */
    val = 3;
    //若第一次发送后收到响应，则后面val -1 次忽略，不需发送
    if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT, &val, sizeof(val)) < 0) {
        anetSetError(err, "setsockopt TCP_KEEPCNT: %s\n", strerror(errno));
        return ANET_ERR;
    }
#else
    ((void) interval); /* Avoid unused var warning for non Linux systems. */
#endif

    return ANET_OK;
}