# HG changeset patch
# Parent  06e7fa209a25f6d35805e6c1e72d785da659a739
Always handle incoming LIFX packet first

This will allow us to more correctly measure the gateways latencies and
fix bugs.

Also good to have the write callbacks executed last once we have can
optimize LIFX packet queues.

diff --git a/core/lightsd.c b/core/lightsd.c
--- a/core/lightsd.c
+++ b/core/lightsd.c
@@ -100,6 +100,10 @@
 {
     event_set_log_callback(lgtd_libevent_log);
     lgtd_ev_base = event_base_new();
+    if (!lgtd_ev_base
+        || event_base_priority_init(lgtd_ev_base, LGTD_EVENT_NPRIORITIES)) {
+        lgtd_err(1, "can't initialize libevent");
+    }
 }
 
 static void
diff --git a/core/lightsd.h b/core/lightsd.h
--- a/core/lightsd.h
+++ b/core/lightsd.h
@@ -83,6 +83,13 @@
 
 enum { LGTD_ERROR_MSG_BUFSIZE = 2048 };
 
+enum {
+    LGTD_EVENT_PRIO_HIGH    = 0,
+    LGTD_EVENT_PRIO_DEFAULT,
+    LGTD_EVENT_PRIO_LOW,
+    LGTD_EVENT_NPRIORITIES
+};
+
 // FIXME: introspect sizeof(sockaddr_un.sun_path) with CMake to generate a
 // reasonable value for that:
 enum { LGTD_SOCKADDR_STRLEN = 128 };
diff --git a/lifx/broadcast.c b/lifx/broadcast.c
--- a/lifx/broadcast.c
+++ b/lifx/broadcast.c
@@ -317,6 +317,13 @@
         goto error;
     }
 
+    err = event_priority_set(
+        lgtd_lifx_broadcast_endpoint.read_ev, LGTD_EVENT_PRIO_HIGH
+    );
+    if (err) {
+        goto error;
+    }
+
     if (!event_add(lgtd_lifx_broadcast_endpoint.read_ev, NULL)) {
         return true;
     }
diff --git a/lifx/gateway.c b/lifx/gateway.c
--- a/lifx/gateway.c
+++ b/lifx/gateway.c
@@ -319,11 +319,13 @@
         gw
     );
     gw->write_buf = evbuffer_new();
-    if (!gw->write_ev || !gw->write_buf) {
-        goto error_allocate;
-    }
     gw->peer = malloc(addrlen);
-    if (!gw->peer) {
+    // We set a low priority on the write callback to be able to "correctly"
+    // measure the latency. In general, we want to process updates from the
+    // bulbs first: better chances of returning up-to-date data to the clients
+    // and to optimize what we're sending to the bulbs:
+    if (!gw->write_ev || !gw->write_buf || !gw->peer
+        || event_priority_set(gw->write_ev, LGTD_EVENT_PRIO_LOW) != 0) {
         goto error_allocate;
     }
 
diff --git a/tests/core/mock_event2.h b/tests/core/mock_event2.h
--- a/tests/core/mock_event2.h
+++ b/tests/core/mock_event2.h
@@ -114,6 +114,16 @@
 }
 #endif
 
+#ifndef MOCKED_EVENT_PRIORITY_SET
+int
+event_priority_set(struct event *ev, int priority)
+{
+    (void)ev;
+    (void)priority;
+    return 0;
+}
+#endif
+
 #ifndef MOCKED_EVENT_ACTIVE
 void
 event_active(struct event *ev, int res, short ncalls)