connSocketEventHandler

定义

connSocketEventHandler 函数负责建立连接，调用 callHandler 完成网络的读写操作，它的实现如下。

static void connSocketEventHandler(struct aeEventLoop *el, int fd, void *clientData, int mask)
{
    UNUSED(el);
    UNUSED(fd);
    connection *conn = clientData;

    if (conn->state == CONN_STATE_CONNECTING &&
            (mask & AE_WRITABLE) && conn->conn_handler) {

        int conn_error = connGetSocketError(conn);
        if (conn_error) {
            conn->last_errno = conn_error;
            conn->state = CONN_STATE_ERROR;
        } else {
            conn->state = CONN_STATE_CONNECTED;
        }

        if (!conn->write_handler) aeDeleteFileEvent(server.el,conn->fd,AE_WRITABLE);

        if (!callHandler(conn, conn->conn_handler)) return;
        conn->conn_handler = NULL;
    }

    /* Normally we execute the readable event first, and the writable
     * event later. This is useful as sometimes we may be able
     * to serve the reply of a query immediately after processing the
     * query.
     *
     * However if WRITE_BARRIER is set in the mask, our application is
     * asking us to do the reverse: never fire the writable event
     * after the readable. In such a case, we invert the calls.
     * This is useful when, for instance, we want to do things
     * in the beforeSleep() hook, like fsync'ing a file to disk,
     * before replying to a client. */
    int invert = conn->flags & CONN_FLAG_WRITE_BARRIER;

    int call_write = (mask & AE_WRITABLE) && conn->write_handler;
    int call_read = (mask & AE_READABLE) && conn->read_handler;

    /* Handle normal I/O flows */
    if (!invert && call_read) {
        if (!callHandler(conn, conn->read_handler)) return;
    }
    /* Fire the writable event. */
    if (call_write) {
        if (!callHandler(conn, conn->write_handler)) return;
    }
    /* If we have to invert the call, fire the readable event now
     * after the writable one. */
    if (invert && call_read) {
        if (!callHandler(conn, conn->read_handler)) return;
    }
}

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connection 对象的定义

connection 在 redis 里面代表一个连接

struct connection {
    ConnectionType *type;
    ConnectionState state;
    short int flags;
    short int refs;
    int last_errno;
    void *private_data;
    ConnectionCallbackFunc conn_handler;
    ConnectionCallbackFunc write_handler;
    ConnectionCallbackFunc read_handler;
    int fd;
};

// ConnectionType 要注意一下是一堆函数指针
typedef struct ConnectionType {
    void (*ae_handler)(struct aeEventLoop *el, int fd, void *clientData, int mask);
    int (*connect)(struct connection *conn, const char *addr, int port, const char *source_addr, ConnectionCallbackFunc connect_handler);
    int (*write)(struct connection *conn, const void *data, size_t data_len);
    int (*writev)(struct connection *conn, const struct iovec *iov, int iovcnt);
    int (*read)(struct connection *conn, void *buf, size_t buf_len);
    void (*close)(struct connection *conn);
    int (*accept)(struct connection *conn, ConnectionCallbackFunc accept_handler);
    int (*set_write_handler)(struct connection *conn, ConnectionCallbackFunc handler, int barrier);
    int (*set_read_handler)(struct connection *conn, ConnectionCallbackFunc handler);
    const char *(*get_last_error)(struct connection *conn);
    int (*blocking_connect)(struct connection *conn, const char *addr, int port, long long timeout);
    ssize_t (*sync_write)(struct connection *conn, char *ptr, ssize_t size, long long timeout);
    ssize_t (*sync_read)(struct connection *conn, char *ptr, ssize_t size, long long timeout);
    ssize_t (*sync_readline)(struct connection *conn, char *ptr, ssize_t size, long long timeout);
    int (*get_type)(struct connection *conn);
} ConnectionType;

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