static void drive_machine(conn *c) {
bool stop = false;
int sfd, flags = 1;
socklen_t addrlen;
struct sockaddr_storage addr;
int nreqs = settings.reqs_per_event;
int res;
assert(c != NULL);
while (!stop) { //注意这里是while循环，也是状态之间可以直接转换的原因。
switch(c->state) {
case conn_listening: //该状态只有dispatcher_thread会进入
addrlen = sizeof(addr);
if ((sfd = accept(c->sfd, (struct sockaddr *)&addr, &addrlen)) == -1) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
/* these are transient, so don't log anything */
stop = true;
} else if (errno == EMFILE) {
if (settings.verbose > 0)
fprintf(stderr, "Too many open connections\n");
accept_new_conns(false);
stop = true;
} else {
perror("accept()");
stop = true;
}
break;
}
if ((flags = fcntl(sfd, F_GETFL, 0)) < 0 ||
fcntl(sfd, F_SETFL, flags | O_NONBLOCK) < 0) {
perror("setting O_NONBLOCK");
close(sfd);
break;
}
//主线程掉用该函数来派发已经accept的connnection, 当worker_thread接受到事件通知处理，其conn的状态为conn_new_cmd,也即worker_thread进入drive_machine的conn_new_cmd状态。
dispatch_conn_new(sfd, conn_new_cmd, EV_READ | EV_PERSIST,
DATA_BUFFER_SIZE, tcp_transport);
stop = true;
break;
case conn_waiting:
if (!update_event(c, EV_READ | EV_PERSIST)) {
if (settings.verbose > 0)
fprintf(stderr, "Couldn't update event\n");
conn_set_state(c, conn_closing);
break;
}
conn_set_state(c, conn_read);
stop = true;
break;
case conn_read:
res = IS_UDP(c->transport) ? try_read_udp(c) : try_read_network(c);
switch (res) {
case READ_NO_DATA_RECEIVED:
conn_set_state(c, conn_waiting);
break;
case READ_DATA_RECEIVED:
conn_set_state(c, conn_parse_cmd);
break;
case READ_ERROR:
conn_set_state(c, conn_closing);
break;
case READ_MEMORY_ERROR: /* Failed to allocate more memory */
/* State already set by try_read_network */
break;
}
break;
case conn_parse_cmd :
if (try_read_command(c) == 0) {
/* wee need more data! */
conn_set_state(c, conn_waiting);
}
break;
case conn_new_cmd:
/* Only process nreqs at a time to avoid starving other
connections */
--nreqs;
if (nreqs >= 0) {
reset_cmd_handler(c);
} else {
pthread_mutex_lock(&c->thread->stats.mutex);
c->thread->stats.conn_yields++;
pthread_mutex_unlock(&c->thread->stats.mutex);
if (c->rbytes > 0) {
/* We have already read in data into the input buffer,
so libevent will most likely not signal read events
on the socket (unless more data is available. As a
hack we should just put in a request to write data,
because that should be possible ;-)
*/
if (!update_event(c, EV_WRITE | EV_PERSIST)) {
if (settings.verbose > 0)
fprintf(stderr, "Couldn't update event\n");
conn_set_state(c, conn_closing);
}
}
stop = true;
}
break;
case conn_nread:
if (c->rlbytes == 0) {
complete_nread(c);
break;
}
/* first check if we have leftovers in the conn_read buffer */
if (c->rbytes > 0) {
int tocopy = c->rbytes > c->rlbytes ? c->rlbytes : c->rbytes;
if (c->ritem != c->rcurr) {
memmove(c->ritem, c->rcurr, tocopy);
}
c->ritem += tocopy;
c->rlbytes -= tocopy;
c->rcurr += tocopy;
c->rbytes -= tocopy;
if (c->rlbytes == 0) {
break;
}
}
/* now try reading from the socket */
res = read(c->sfd, c->ritem, c->rlbytes);
if (res > 0) {
pthread_mutex_lock(&c->thread->stats.mutex);
c->thread->stats.bytes_read += res;
pthread_mutex_unlock(&c->thread->stats.mutex);
if (c->rcurr == c->ritem) {
c->rcurr += res;
}
c->ritem += res;
c->rlbytes -= res;
break;
}
if (res == 0) { /* end of stream */
conn_set_state(c, conn_closing);
break;
}
if (res == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
if (!update_event(c, EV_READ | EV_PERSIST)) {
if (settings.verbose > 0)
fprintf(stderr, "Couldn't update event\n");
conn_set_state(c, conn_closing);
break;
}
stop = true;
break;
}
/* otherwise we have a real error, on which we close the connection */
if (settings.verbose > 0) {
fprintf(stderr, "Failed to read, and not due to blocking:\n"
"errno: %d %s \n"
"rcurr=%lx ritem=%lx rbuf=%lx rlbytes=%d rsize=%d\n",
errno, strerror(errno),
(long)c->rcurr, (long)c->ritem, (long)c->rbuf,
(int)c->rlbytes, (int)c->rsize);
}
conn_set_state(c, conn_closing);
break;
case conn_swallow:
/* we are reading sbytes and throwing them away */
if (c->sbytes == 0) {
conn_set_state(c, conn_new_cmd);
break;
}
/* first check if we have leftovers in the conn_read buffer */
if (c->rbytes > 0) {
int tocopy = c->rbytes > c->sbytes ? c->sbytes : c->rbytes;
c->sbytes -= tocopy;
c->rcurr += tocopy;
c->rbytes -= tocopy;
break;
}
/* now try reading from the socket */
res = read(c->sfd, c->rbuf, c->rsize > c->sbytes ? c->sbytes : c->rsize);
if (res > 0) {
pthread_mutex_lock(&c->thread->stats.mutex);
c->thread->stats.bytes_read += res;
pthread_mutex_unlock(&c->thread->stats.mutex);
c->sbytes -= res;
break;
}
if (res == 0) { /* end of stream */
conn_set_state(c, conn_closing);
break;
}
if (res == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
if (!update_event(c, EV_READ | EV_PERSIST)) {
if (settings.verbose > 0)
fprintf(stderr, "Couldn't update event\n");
conn_set_state(c, conn_closing);
break;
}
stop = true;
break;
}
/* otherwise we have a real error, on which we close the connection */
if (settings.verbose > 0)
fprintf(stderr, "Failed to read, and not due to blocking\n");
conn_set_state(c, conn_closing);
break;
case conn_write:
/*
* We want to write out a simple response. If we haven't already,
* assemble it into a msgbuf list (this will be a single-entry
* list for TCP or a two-entry list for UDP).
*/
if (c->iovused == 0 || (IS_UDP(c->transport) && c->iovused == 1)) {
if (add_iov(c, c->wcurr, c->wbytes) != 0) {
if (settings.verbose > 0)
fprintf(stderr, "Couldn't build response\n");
conn_set_state(c, conn_closing);
break;
}
}
/* fall through... */
case conn_mwrite:
if (IS_UDP(c->transport) && c->msgcurr == 0 && build_udp_headers(c) != 0) {
if (settings.verbose > 0)
fprintf(stderr, "Failed to build UDP headers\n");
conn_set_state(c, conn_closing);
break;
}
switch (transmit(c)) {
case TRANSMIT_COMPLETE:
if (c->state == conn_mwrite) {
while (c->ileft > 0) {
item *it = *(c->icurr);
assert((it->it_flags & ITEM_SLABBED) == 0);
item_remove(it);
c->icurr++;
c->ileft--;
}
while (c->suffixleft > 0) {
char *suffix = *(c->suffixcurr);
cache_free(c->thread->suffix_cache, suffix);
c->suffixcurr++;
c->suffixleft--;
}
/* XXX: I don't know why this wasn't the general case */
if(c->protocol == binary_prot) {
conn_set_state(c, c->write_and_go);
} else {
conn_set_state(c, conn_new_cmd);
}
} else if (c->state == conn_write) {
if (c->write_and_free) {
free(c->write_and_free);
c->write_and_free = 0;
}
conn_set_state(c, c->write_and_go);
} else {
if (settings.verbose > 0)
fprintf(stderr, "Unexpected state %d\n", c->state);
conn_set_state(c, conn_closing);
}
break;
case TRANSMIT_INCOMPLETE:
case TRANSMIT_HARD_ERROR:
break; /* Continue in state machine. */
case TRANSMIT_SOFT_ERROR:
stop = true;
break;
}
break;
case conn_closing:
if (IS_UDP(c->transport))
conn_cleanup(c);
else
conn_close(c);
stop = true;
break;
case conn_max_state:
assert(false);
break;
}
}
return;
}
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