Function clusterReadHandler

app/redis-6.2.6/src/cluster.c:2320–2390

Read data. Try to read the first field of the header first to check the * full length of the packet. When a whole packet is in memory this function * will call the function to process the packet. And so forth. */

 * full length of the packet. When a whole packet is in memory this function
 * will call the function to process the packet. And so forth. */
void clusterReadHandler(connection *conn) {
    clusterMsg buf[1];
    ssize_t nread;
    clusterMsg *hdr;
    clusterLink *link = connGetPrivateData(conn);
    unsigned int readlen, rcvbuflen;

    while(1) { /* Read as long as there is data to read. */
        rcvbuflen = link->rcvbuf_len;
        if (rcvbuflen < 8) {
            /* First, obtain the first 8 bytes to get the full message
             * length. */
            readlen = 8 - rcvbuflen;
        } else {
            /* Finally read the full message. */
            hdr = (clusterMsg*) link->rcvbuf;
            if (rcvbuflen == 8) {
                /* Perform some sanity check on the message signature
                 * and length. */
                if (memcmp(hdr->sig,"RCmb",4) != 0 ||
                    ntohl(hdr->totlen) < CLUSTERMSG_MIN_LEN)
                {
                    serverLog(LL_WARNING,
                        "Bad message length or signature received "
                        "from Cluster bus.");
                    handleLinkIOError(link);
                    return;
                }
            }
            readlen = ntohl(hdr->totlen) - rcvbuflen;
            if (readlen > sizeof(buf)) readlen = sizeof(buf);
        }

        nread = connRead(conn,buf,readlen);
        if (nread == -1 && (connGetState(conn) == CONN_STATE_CONNECTED)) return; /* No more data ready. */

        if (nread <= 0) {
            /* I/O error... */
            serverLog(LL_DEBUG,"I/O error reading from node link: %s",
                (nread == 0) ? "connection closed" : connGetLastError(conn));
            handleLinkIOError(link);
            return;
        } else {
            /* Read data and recast the pointer to the new buffer. */
            size_t unused = link->rcvbuf_alloc - link->rcvbuf_len;
            if ((size_t)nread > unused) {
                size_t required = link->rcvbuf_len + nread;
                /* If less than 1mb, grow to twice the needed size, if larger grow by 1mb. */
                link->rcvbuf_alloc = required < RCVBUF_MAX_PREALLOC ? required * 2: required + RCVBUF_MAX_PREALLOC;
                link->rcvbuf = zrealloc(link->rcvbuf, link->rcvbuf_alloc);
            }
            memcpy(link->rcvbuf + link->rcvbuf_len, buf, nread);
            link->rcvbuf_len += nread;
            hdr = (clusterMsg*) link->rcvbuf;
            rcvbuflen += nread;
        }

        /* Total length obtained? Process this packet. */