proxy: backend connection improvement

Improvements to handling of new and failed backend socket connections.

Previously connections were initiated immediately, and initially from
the config thread, yet completion of opening sockets wouldn't happen
until a request tried to use that backend.

Now we open connections via the IO thread, as well as validate new
connections with a "version\r\n" command.

Also fixes a couple of error conditions (parsing, backend disconnect)
where clients could hang waiting for a retry time in certain conditions.
Now connections should re-establish immediately and dead backends should
flip into a bad fast-fail state quicker.

1 files changed, 13 insertions, 0 deletions

diff --git a/proto_proxy.c b/proto_proxy.c
index d39b7b1..a654b92 100644
--- a/proto_proxy.c
+++ b/proto_proxy.c
@@ -146,6 +146,11 @@ void *proxy_init(bool use_uring) {
             perror("failed to create backend notify eventfd");
             exit(1);
         }
+        t->be_event_fd = eventfd(0, EFD_NONBLOCK);
+        if (t->be_event_fd == -1) {
+            perror("failed to create backend notify eventfd");
+            exit(1);
+        }
 #else
         int fds[2];
         if (pipe(fds)) {
@@ -155,11 +160,19 @@ void *proxy_init(bool use_uring) {
 
         t->notify_receive_fd = fds[0];
         t->notify_send_fd = fds[1];
+
+        if (pipe(fds)) {
+            perror("can't create proxy backend connection notify pipe");
+            exit(1);
+        }
+        t->be_notify_receive_fd = fds[0];
+        t->be_notify_send_fd = fds[1];
 #endif
         proxy_init_evthread_events(t);
 
         // incoming request queue.
         STAILQ_INIT(&t->io_head_in);
+        STAILQ_INIT(&t->beconn_head_in);
         pthread_mutex_init(&t->mutex, NULL);
         pthread_cond_init(&t->cond, NULL);