session: app mq congestion detection

Detect mq congestion and handle it by queueing messages in a fifo and
postponing handling via rpcs. App workers with congested mqs cannot
accept nor connect additional sessions.

Type: feature

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I401d971a1a53896758b88fc60f158cbc31e0c7cb

3 files changed, 349 insertions, 266 deletions

diff --git a/src/vnet/session/application.h b/src/vnet/session/application.h
index b3201b9833e..54a616a99b1 100644
--- a/src/vnet/session/application.h
+++ b/src/vnet/session/application.h
@@ -29,6 +29,16 @@
 #define APP_DBG(_fmt, _args...)
 #endif
 
+typedef struct app_wrk_postponed_msg_
+{
+  u32 len;
+  u8 event_type;
+  u8 ring;
+  u8 is_sapi;
+  int fd;
+  u8 data[SESSION_CTRL_MSG_MAX_SIZE];
+} app_wrk_postponed_msg_t;
+
 typedef struct app_worker_
 {
   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
@@ -59,6 +69,9 @@ typedef struct app_worker_
   /** API index for the worker. Needed for multi-process apps */
   u32 api_client_index;
 
+  /** Set if mq is congested */
+  u8 mq_congested;
+
   u8 app_is_builtin;
 
   /** Pool of half-open session handles. Tracked in case worker detaches */
@@ -69,6 +82,12 @@ typedef struct app_worker_
 
   /** Vector of detached listener segment managers */
   u32 *detached_seg_managers;
+
+  /** Fifo of messages postponed because of mq congestion */
+  app_wrk_postponed_msg_t *postponed_mq_msgs;
+
+  /** Lock to add/sub message from ref @postponed_mq_msgs */
+  clib_spinlock_t postponed_mq_msgs_lock;
 } app_worker_t;
 
 typedef struct app_worker_map_
@@ -339,6 +358,10 @@ int app_worker_del_segment_notify (app_worker_t * app_wrk,
 u32 app_worker_n_listeners (app_worker_t * app);
 session_t *app_worker_first_listener (app_worker_t * app,
 				      u8 fib_proto, u8 transport_proto);
+void app_wrk_send_ctrl_evt_fd (app_worker_t *app_wrk, u8 evt_type, void *msg,
+			       u32 msg_len, int fd);
+void app_wrk_send_ctrl_evt (app_worker_t *app_wrk, u8 evt_type, void *msg,
+			    u32 msg_len);
 int app_worker_send_event (app_worker_t * app, session_t * s, u8 evt);
 int app_worker_lock_and_send_event (app_worker_t * app, session_t * s,
 				    u8 evt_type);
diff --git a/src/vnet/session/application_worker.c b/src/vnet/session/application_worker.c
index 54377604803..6bbad045d0d 100644
--- a/src/vnet/session/application_worker.c
+++ b/src/vnet/session/application_worker.c
@@ -33,6 +33,7 @@ app_worker_alloc (application_t * app)
   app_wrk->wrk_map_index = ~0;
   app_wrk->connects_seg_manager = APP_INVALID_SEGMENT_MANAGER_INDEX;
   clib_spinlock_init (&app_wrk->detached_seg_managers_lock);
+  clib_spinlock_init (&app_wrk->postponed_mq_msgs_lock);
   APP_DBG ("New app %v worker %u", app->name, app_wrk->wrk_index);
   return app_wrk;
 }
@@ -126,6 +127,7 @@ app_worker_free (app_worker_t * app_wrk)
     }
   vec_free (app_wrk->detached_seg_managers);
   clib_spinlock_free (&app_wrk->detached_seg_managers_lock);
+  clib_spinlock_free (&app_wrk->postponed_mq_msgs_lock);
 
   if (CLIB_DEBUG)
     clib_memset (app_wrk, 0xfe, sizeof (*app_wrk));
@@ -338,8 +340,10 @@ app_worker_init_accepted (session_t * s)
 
   listener = listen_session_get_from_handle (s->listener_handle);
   app_wrk = application_listener_select_worker (listener);
-  s->app_wrk_index = app_wrk->wrk_index;
+  if (PREDICT_FALSE (app_wrk->mq_congested))
+    return -1;
 
+  s->app_wrk_index = app_wrk->wrk_index;
   app = application_get (app_wrk->app_index);
   if (app->cb_fns.fifo_tuning_callback)
     s->flags |= SESSION_F_CUSTOM_FIFO_TUNING;
@@ -510,6 +514,9 @@ int
 app_worker_connect_session (app_worker_t *app_wrk, session_endpoint_cfg_t *sep,
 			    session_handle_t *rsh)
 {
+  if (PREDICT_FALSE (app_wrk->mq_congested))
+    return SESSION_E_REFUSED;
+
   sep->app_wrk_index = app_wrk->wrk_index;
 
   return session_open (sep, rsh);
@@ -614,12 +621,240 @@ app_worker_application_is_builtin (app_worker_t * app_wrk)
   return app_wrk->app_is_builtin;
 }
 
+static int
+app_wrk_send_fd (app_worker_t *app_wrk, int fd)
+{
+  if (!appns_sapi_enabled ())
+    {
+      vl_api_registration_t *reg;
+      clib_error_t *error;
+
+      reg =
+	vl_mem_api_client_index_to_registration (app_wrk->api_client_index);
+      if (!reg)
+	{
+	  clib_warning ("no api registration for client: %u",
+			app_wrk->api_client_index);
+	  return -1;
+	}
+
+      if (vl_api_registration_file_index (reg) == VL_API_INVALID_FI)
+	return -1;
+
+      error = vl_api_send_fd_msg (reg, &fd, 1);
+      if (error)
+	{
+	  clib_error_report (error);
+	  return -1;
+	}
+
+      return 0;
+    }
+
+  app_sapi_msg_t smsg = { 0 };
+  app_namespace_t *app_ns;
+  clib_error_t *error;
+  application_t *app;
+  clib_socket_t *cs;
+  u32 cs_index;
+
+  app = application_get (app_wrk->app_index);
+  app_ns = app_namespace_get (app->ns_index);
+  cs_index = appns_sapi_handle_sock_index (app_wrk->api_client_index);
+  cs = appns_sapi_get_socket (app_ns, cs_index);
+  if (PREDICT_FALSE (!cs))
+    return -1;
+
+  /* There's no payload for the message only the type */
+  smsg.type = APP_SAPI_MSG_TYPE_SEND_FDS;
+  error = clib_socket_sendmsg (cs, &smsg, sizeof (smsg), &fd, 1);
+  if (error)
+    {
+      clib_error_report (error);
+      return -1;
+    }
+
+  return 0;
+}
+
+static int
+mq_try_lock_and_alloc_msg (svm_msg_q_t *mq, session_mq_rings_e ring,
+			   svm_msg_q_msg_t *msg)
+{
+  int rv, n_try = 0;
+
+  while (n_try < 5)
+    {
+      rv = svm_msg_q_lock_and_alloc_msg_w_ring (mq, ring, SVM_Q_NOWAIT, msg);
+      if (!rv)
+	return 0;
+      /*
+       * Break the loop if mq is full, usually this is because the
+       * app has crashed or is hanging on somewhere.
+       */
+      if (rv != -1)
+	break;
+      n_try += 1;
+      usleep (1);
+    }
+
+  return -1;
+}
+
+typedef union app_wrk_mq_rpc_args_
+{
+  struct
+  {
+    u32 thread_index;
+    u32 app_wrk_index;
+  };
+  uword as_uword;
+} app_wrk_mq_rpc_ags_t;
+
+static int
+app_wrk_handle_mq_postponed_msgs (void *arg)
+{
+  svm_msg_q_msg_t _mq_msg, *mq_msg = &_mq_msg;
+  app_wrk_postponed_msg_t *pm;
+  app_wrk_mq_rpc_ags_t args;
+  u32 max_msg, n_msg = 0;
+  app_worker_t *app_wrk;
+  session_event_t *evt;
+  svm_msg_q_t *mq;
+
+  args.as_uword = pointer_to_uword (arg);
+  app_wrk = app_worker_get_if_valid (args.app_wrk_index);
+  if (!app_wrk)
+    return 0;
+
+  mq = app_wrk->event_queue;
+
+  clib_spinlock_lock (&app_wrk->postponed_mq_msgs_lock);
+
+  max_msg = clib_min (32, clib_fifo_elts (app_wrk->postponed_mq_msgs));
+
+  while (n_msg < max_msg)
+    {
+      pm = clib_fifo_head (app_wrk->postponed_mq_msgs);
+      if (mq_try_lock_and_alloc_msg (mq, pm->ring, mq_msg))
+	break;
+
+      evt = svm_msg_q_msg_data (mq, mq_msg);
+      clib_memset (evt, 0, sizeof (*evt));
+      evt->event_type = pm->event_type;
+      clib_memcpy_fast (evt->data, pm->data, pm->len);
+
+      if (pm->fd != -1)
+	app_wrk_send_fd (app_wrk, pm->fd);
+
+      svm_msg_q_add_and_unlock (mq, mq_msg);
+
+      clib_fifo_advance_head (app_wrk->postponed_mq_msgs, 1);
+      n_msg += 1;
+    }
+
+  if (!clib_fifo_elts (app_wrk->postponed_mq_msgs))
+    {
+      app_wrk->mq_congested = 0;
+    }
+  else
+    {
+      session_send_rpc_evt_to_thread_force (
+	args.thread_index, app_wrk_handle_mq_postponed_msgs,
+	uword_to_pointer (args.as_uword, void *));
+    }
+
+  clib_spinlock_unlock (&app_wrk->postponed_mq_msgs_lock);
+
+  return 0;
+}
+
+static void
+app_wrk_add_mq_postponed_msg (app_worker_t *app_wrk, session_mq_rings_e ring,
+			      u8 evt_type, void *msg, u32 msg_len, int fd)
+{
+  app_wrk_postponed_msg_t *pm;
+
+  clib_spinlock_lock (&app_wrk->postponed_mq_msgs_lock);
+
+  app_wrk->mq_congested = 1;
+
+  clib_fifo_add2 (app_wrk->postponed_mq_msgs, pm);
+  clib_memcpy_fast (pm->data, msg, msg_len);
+  pm->event_type = evt_type;
+  pm->ring = ring;
+  pm->len = msg_len;
+  pm->fd = fd;
+
+  if (clib_fifo_elts (app_wrk->postponed_mq_msgs) == 1)
+    {
+      app_wrk_mq_rpc_ags_t args = { .thread_index = vlib_get_thread_index (),
+				    .app_wrk_index = app_wrk->wrk_index };
+
+      session_send_rpc_evt_to_thread_force (
+	args.thread_index, app_wrk_handle_mq_postponed_msgs,
+	uword_to_pointer (args.as_uword, void *));
+    }
+
+  clib_spinlock_unlock (&app_wrk->postponed_mq_msgs_lock);
+}
+
+always_inline void
+app_wrk_send_ctrl_evt_inline (app_worker_t *app_wrk, u8 evt_type, void *msg,
+			      u32 msg_len, int fd)
+{
+  svm_msg_q_msg_t _mq_msg, *mq_msg = &_mq_msg;
+  svm_msg_q_t *mq = app_wrk->event_queue;
+  session_event_t *evt;
+  int rv;
+
+  if (PREDICT_FALSE (app_wrk->mq_congested))
+    goto handle_congestion;
+
+  rv = mq_try_lock_and_alloc_msg (mq, SESSION_MQ_CTRL_EVT_RING, mq_msg);
+  if (PREDICT_FALSE (rv))
+    goto handle_congestion;
+
+  evt = svm_msg_q_msg_data (mq, mq_msg);
+  clib_memset (evt, 0, sizeof (*evt));
+  evt->event_type = evt_type;
+  clib_memcpy_fast (evt->data, msg, msg_len);
+
+  if (fd != -1)
+    app_wrk_send_fd (app_wrk, fd);
+
+  svm_msg_q_add_and_unlock (mq, mq_msg);
+
+  return;
+
+handle_congestion:
+
+  app_wrk_add_mq_postponed_msg (app_wrk, SESSION_MQ_CTRL_EVT_RING, evt_type,
+				msg, msg_len, fd);
+}
+
+void
+app_wrk_send_ctrl_evt_fd (app_worker_t *app_wrk, u8 evt_type, void *msg,
+			  u32 msg_len, int fd)
+{
+  app_wrk_send_ctrl_evt_inline (app_wrk, evt_type, msg, msg_len, fd);
+}
+
+void
+app_wrk_send_ctrl_evt (app_worker_t *app_wrk, u8 evt_type, void *msg,
+		       u32 msg_len)
+{
+  app_wrk_send_ctrl_evt_inline (app_wrk, evt_type, msg, msg_len, -1);
+}
+
 static inline int
 app_send_io_evt_rx (app_worker_t * app_wrk, session_t * s)
 {
+  svm_msg_q_msg_t _mq_msg = { 0 }, *mq_msg = &_mq_msg;
   session_event_t *evt;
-  svm_msg_q_msg_t msg;
   svm_msg_q_t *mq;
+  u32 app_session;
+  int rv;
 
   if (app_worker_application_is_builtin (app_wrk))
     return app_worker_builtin_rx (app_wrk, s);
@@ -627,68 +862,72 @@ app_send_io_evt_rx (app_worker_t * app_wrk, session_t * s)
   if (svm_fifo_has_event (s->rx_fifo))
     return 0;
 
+  app_session = s->rx_fifo->shr->client_session_index;
   mq = app_wrk->event_queue;
-  svm_msg_q_lock (mq);
 
-  if (PREDICT_FALSE (svm_msg_q_is_full (mq)))
-    {
-      clib_warning ("evt q full");
-      svm_msg_q_unlock (mq);
-      return -1;
-    }
+  if (PREDICT_FALSE (app_wrk->mq_congested))
+    goto handle_congestion;
 
-  if (PREDICT_FALSE (svm_msg_q_ring_is_full (mq, SESSION_MQ_IO_EVT_RING)))
-    {
-      clib_warning ("evt q rings full");
-      svm_msg_q_unlock (mq);
-      return -1;
-    }
+  rv = mq_try_lock_and_alloc_msg (mq, SESSION_MQ_IO_EVT_RING, mq_msg);
 
-  msg = svm_msg_q_alloc_msg_w_ring (mq, SESSION_MQ_IO_EVT_RING);
-  evt = (session_event_t *) svm_msg_q_msg_data (mq, &msg);
-  evt->session_index = s->rx_fifo->shr->client_session_index;
+  if (PREDICT_FALSE (rv))
+    goto handle_congestion;
+
+  evt = svm_msg_q_msg_data (mq, mq_msg);
   evt->event_type = SESSION_IO_EVT_RX;
+  evt->session_index = app_session;
 
   (void) svm_fifo_set_event (s->rx_fifo);
-  svm_msg_q_add_and_unlock (mq, &msg);
+
+  svm_msg_q_add_and_unlock (mq, mq_msg);
 
   return 0;
+
+handle_congestion:
+
+  app_wrk_add_mq_postponed_msg (app_wrk, SESSION_MQ_IO_EVT_RING,
+				SESSION_IO_EVT_RX, &app_session,
+				sizeof (app_session), -1);
+  return -1;
 }
 
 static inline int
 app_send_io_evt_tx (app_worker_t * app_wrk, session_t * s)
 {
-  svm_msg_q_t *mq;
+  svm_msg_q_msg_t _mq_msg = { 0 }, *mq_msg = &_mq_msg;
   session_event_t *evt;
-  svm_msg_q_msg_t msg;
+  svm_msg_q_t *mq;
+  u32 app_session;
+  int rv;
 
   if (app_worker_application_is_builtin (app_wrk))
     return app_worker_builtin_tx (app_wrk, s);
 
+  app_session = s->tx_fifo->shr->client_session_index;
   mq = app_wrk->event_queue;
-  svm_msg_q_lock (mq);
 
-  if (PREDICT_FALSE (svm_msg_q_is_full (mq)))
-    {
-      clib_warning ("evt q full");
-      svm_msg_q_unlock (mq);
-      return -1;
-    }
+  if (PREDICT_FALSE (app_wrk->mq_congested))
+    goto handle_congestion;
 
-  if (PREDICT_FALSE (svm_msg_q_ring_is_full (mq, SESSION_MQ_IO_EVT_RING)))
-    {
-      clib_warning ("evt q rings full");
-      svm_msg_q_unlock (mq);
-      return -1;
-    }
+  rv = mq_try_lock_and_alloc_msg (mq, SESSION_MQ_IO_EVT_RING, mq_msg);
+
+  if (PREDICT_FALSE (rv))
+    goto handle_congestion;
 
-  msg = svm_msg_q_alloc_msg_w_ring (mq, SESSION_MQ_IO_EVT_RING);
-  evt = (session_event_t *) svm_msg_q_msg_data (mq, &msg);
+  evt = svm_msg_q_msg_data (mq, mq_msg);
   evt->event_type = SESSION_IO_EVT_TX;
-  evt->session_index = s->tx_fifo->shr->client_session_index;
+  evt->session_index = app_session;
+
+  svm_msg_q_add_and_unlock (mq, mq_msg);
 
-  svm_msg_q_add_and_unlock (mq, &msg);
   return 0;
+
+handle_congestion:
+
+  app_wrk_add_mq_postponed_msg (app_wrk, SESSION_MQ_IO_EVT_RING,
+				SESSION_IO_EVT_TX, &app_session,
+				sizeof (app_session), -1);
+  return -1;
 }
 
 /* *INDENT-OFF* */
@@ -764,10 +1003,12 @@ format_app_worker (u8 * s, va_list * args)
   app_worker_t *app_wrk = va_arg (*args, app_worker_t *);
   u32 indent = 1;
 
-  s = format (s, "%U wrk-index %u app-index %u map-index %u "
-	      "api-client-index %d\n", format_white_space, indent,
-	      app_wrk->wrk_index, app_wrk->app_index, app_wrk->wrk_map_index,
-	      app_wrk->api_client_index);
+  s = format (s,
+	      "%U wrk-index %u app-index %u map-index %u "
+	      "api-client-index %d mq-cong %u\n",
+	      format_white_space, indent, app_wrk->wrk_index,
+	      app_wrk->app_index, app_wrk->wrk_map_index,
+	      app_wrk->api_client_index, app_wrk->mq_congested);
   return s;
 }
 
diff --git a/src/vnet/session/session_api.c b/src/vnet/session/session_api.c
index 767a24aa170..f6170debba7 100644
--- a/src/vnet/session/session_api.c
+++ b/src/vnet/session/session_api.c
@@ -82,40 +82,12 @@ session_send_fds (vl_api_registration_t * reg, int fds[], int n_fds)
 }
 
 static int
-mq_try_lock_and_alloc_msg (svm_msg_q_t * app_mq, svm_msg_q_msg_t * msg)
-{
-  int rv;
-  u8 try = 0;
-  while (try < 100)
-    {
-      rv = svm_msg_q_lock_and_alloc_msg_w_ring (app_mq,
-						SESSION_MQ_CTRL_EVT_RING,
-						SVM_Q_NOWAIT, msg);
-      if (!rv)
-	return 0;
-      /*
-       * Break the loop if mq is full, usually this is because the
-       * app has crashed or is hanging on somewhere.
-       */
-      if (rv != -1)
-	break;
-      try++;
-      usleep (1);
-    }
-  clib_warning ("failed to alloc msg");
-  return -1;
-}
-
-static int
 mq_send_session_accepted_cb (session_t * s)
 {
   app_worker_t *app_wrk = app_worker_get (s->app_wrk_index);
-  svm_msg_q_msg_t _msg, *msg = &_msg;
   session_accepted_msg_t m = { 0 };
-  svm_msg_q_t *app_mq;
   fifo_segment_t *eq_seg;
   session_t *listener;
-  session_event_t *evt;
   application_t *app;
 
   app = application_get (app_wrk->app_index);
@@ -164,15 +136,7 @@ mq_send_session_accepted_cb (session_t * s)
       m.mq_index = s->thread_index;
     }
 
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return SESSION_E_MQ_MSG_ALLOC;
-
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_ACCEPTED;
-  clib_memcpy_fast (evt->data, &m, sizeof (m));
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_ACCEPTED, &m, sizeof (m));
 
   return 0;
 }
@@ -181,21 +145,12 @@ static inline void
 mq_send_session_close_evt (app_worker_t * app_wrk, session_handle_t sh,
 			   session_evt_type_t evt_type)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_disconnected_msg_t *mp;
-  svm_msg_q_t *app_mq;
-  session_event_t *evt;
+  session_disconnected_msg_t m = { 0 };
 
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return;
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = evt_type;
-  mp = (session_disconnected_msg_t *) evt->data;
-  mp->handle = sh;
-  mp->context = app_wrk->api_client_index;
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  m.handle = sh;
+  m.context = app_wrk->api_client_index;
+
+  app_wrk_send_ctrl_evt (app_wrk, evt_type, &m, sizeof (m));
 }
 
 static inline void
@@ -249,13 +204,10 @@ int
 mq_send_session_connected_cb (u32 app_wrk_index, u32 api_context,
 			      session_t * s, session_error_t err)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
   session_connected_msg_t m = { 0 };
-  svm_msg_q_t *app_mq;
   transport_connection_t *tc;
   fifo_segment_t *eq_seg;
   app_worker_t *app_wrk;
-  session_event_t *evt;
   application_t *app;
 
   app_wrk = app_worker_get (app_wrk_index);
@@ -318,17 +270,8 @@ mq_send_session_connected_cb (u32 app_wrk_index, u32 api_context,
 
 snd_msg:
 
-  app_mq = app_wrk->event_queue;
-
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return SESSION_E_MQ_MSG_ALLOC;
-
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_CONNECTED;
-  clib_memcpy_fast (evt->data, &m, sizeof (m));
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_CONNECTED, &m, sizeof (m));
 
-  svm_msg_q_add_and_unlock (app_mq, msg);
   return 0;
 }
 
@@ -336,13 +279,10 @@ int
 mq_send_session_bound_cb (u32 app_wrk_index, u32 api_context,
 			  session_handle_t handle, int rv)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
   session_bound_msg_t m = { 0 };
-  svm_msg_q_t *app_mq;
   transport_endpoint_t tep;
   fifo_segment_t *eq_seg;
   app_worker_t *app_wrk;
-  session_event_t *evt;
   application_t *app;
   app_listener_t *al;
   session_t *ls = 0;
@@ -381,17 +321,8 @@ mq_send_session_bound_cb (u32 app_wrk_index, u32 api_context,
 
 snd_msg:
 
-  app_mq = app_wrk->event_queue;
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_BOUND, &m, sizeof (m));
 
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return SESSION_E_MQ_MSG_ALLOC;
-
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_BOUND;
-  clib_memcpy_fast (evt->data, &m, sizeof (m));
-
-  svm_msg_q_add_and_unlock (app_mq, msg);
   return 0;
 }
 
@@ -399,40 +330,26 @@ void
 mq_send_unlisten_reply (app_worker_t * app_wrk, session_handle_t sh,
 			u32 context, int rv)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_unlisten_reply_msg_t *ump;
-  svm_msg_q_t *app_mq;
-  session_event_t *evt;
-
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return;
+  session_unlisten_reply_msg_t m = { 0 };
 
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_UNLISTEN_REPLY;
-  ump = (session_unlisten_reply_msg_t *) evt->data;
-  ump->context = context;
-  ump->handle = sh;
-  ump->retval = rv;
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  m.context = context;
+  m.handle = sh;
+  m.retval = rv;
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_UNLISTEN_REPLY, &m,
+			 sizeof (m));
 }
 
 static void
 mq_send_session_migrate_cb (session_t * s, session_handle_t new_sh)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
   session_migrated_msg_t m = { 0 };
   fifo_segment_t *eq_seg;
   app_worker_t *app_wrk;
-  session_event_t *evt;
-  svm_msg_q_t *app_mq;
   application_t *app;
   u32 thread_index;
 
   thread_index = session_thread_from_handle (new_sh);
   app_wrk = app_worker_get (s->app_wrk_index);
-  app_mq = app_wrk->event_queue;
   app = application_get (app_wrk->app_index);
   eq_seg = application_get_rx_mqs_segment (app);
 
@@ -442,27 +359,15 @@ mq_send_session_migrate_cb (session_t * s, session_handle_t new_sh)
   m.vpp_evt_q = fifo_segment_msg_q_offset (eq_seg, thread_index);
   m.segment_handle = SESSION_INVALID_HANDLE;
 
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return;
-
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_MIGRATED;
-  clib_memcpy_fast (evt->data, &m, sizeof (m));
-
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_MIGRATED, &m, sizeof (m));
 }
 
 static int
 mq_send_add_segment_cb (u32 app_wrk_index, u64 segment_handle)
 {
-  int fds[SESSION_N_FD_TYPE], n_fds = 0;
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_app_add_segment_msg_t *mp;
+  session_app_add_segment_msg_t m = { 0 };
   vl_api_registration_t *reg;
   app_worker_t *app_wrk;
-  session_event_t *evt;
-  svm_msg_q_t *app_mq;
   fifo_segment_t *fs;
   ssvm_private_t *sp;
   u8 fd_flags = 0;
@@ -488,29 +393,16 @@ mq_send_add_segment_cb (u32 app_wrk_index, u64 segment_handle)
 	}
 
       fd_flags |= SESSION_FD_F_MEMFD_SEGMENT;
-      fds[n_fds] = sp->fd;
-      n_fds += 1;
     }
 
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return -1;
-
-  if (n_fds)
-    session_send_fds (reg, fds, n_fds);
-
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_APP_ADD_SEGMENT;
-  mp = (session_app_add_segment_msg_t *) evt->data;
-  clib_memset (mp, 0, sizeof (*mp));
-  mp->segment_size = sp->ssvm_size;
-  mp->fd_flags = fd_flags;
-  mp->segment_handle = segment_handle;
-  strncpy ((char *) mp->segment_name, (char *) sp->name,
-	   sizeof (mp->segment_name) - 1);
+  m.segment_size = sp->ssvm_size;
+  m.fd_flags = fd_flags;
+  m.segment_handle = segment_handle;
+  strncpy ((char *) m.segment_name, (char *) sp->name,
+	   sizeof (m.segment_name) - 1);
 
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt_fd (app_wrk, SESSION_CTRL_EVT_APP_ADD_SEGMENT, &m,
+			    sizeof (m), sp->fd);
 
   return 0;
 }
@@ -518,12 +410,9 @@ mq_send_add_segment_cb (u32 app_wrk_index, u64 segment_handle)
 static int
 mq_send_del_segment_cb (u32 app_wrk_index, u64 segment_handle)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_app_del_segment_msg_t *mp;
+  session_app_del_segment_msg_t m = { 0 };
   vl_api_registration_t *reg;
   app_worker_t *app_wrk;
-  session_event_t *evt;
-  svm_msg_q_t *app_mq;
 
   app_wrk = app_worker_get (app_wrk_index);
   reg = vl_mem_api_client_index_to_registration (app_wrk->api_client_index);
@@ -533,17 +422,10 @@ mq_send_del_segment_cb (u32 app_wrk_index, u64 segment_handle)
       return -1;
     }
 
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return -1;
+  m.segment_handle = segment_handle;
 
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_APP_DEL_SEGMENT;
-  mp = (session_app_del_segment_msg_t *) evt->data;
-  clib_memset (mp, 0, sizeof (*mp));
-  mp->segment_handle = segment_handle;
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_APP_DEL_SEGMENT, &m,
+			 sizeof (m));
 
   return 0;
 }
@@ -551,10 +433,7 @@ mq_send_del_segment_cb (u32 app_wrk_index, u64 segment_handle)
 static void
 mq_send_session_cleanup_cb (session_t * s, session_cleanup_ntf_t ntf)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_cleanup_msg_t *mp;
-  svm_msg_q_t *app_mq;
-  session_event_t *evt;
+  session_cleanup_msg_t m = { 0 };
   app_worker_t *app_wrk;
 
   /* Propagate transport cleanup notifications only if app didn't close */
@@ -566,17 +445,10 @@ mq_send_session_cleanup_cb (session_t * s, session_cleanup_ntf_t ntf)
   if (!app_wrk)
     return;
 
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return;
+  m.handle = session_handle (s);
+  m.type = ntf;
 
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_CLEANUP;
-  mp = (session_cleanup_msg_t *) evt->data;
-  mp->handle = session_handle (s);
-  mp->type = ntf;
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_CLEANUP, &m, sizeof (m));
 }
 
 static session_cb_vft_t session_mq_cb_vft = {
@@ -1245,36 +1117,11 @@ VL_MSG_API_REAPER_FUNCTION (application_reaper_cb);
  * Socket api functions
  */
 
-static void
-sapi_send_fds (app_worker_t * app_wrk, int *fds, int n_fds)
-{
-  app_sapi_msg_t smsg = { 0 };
-  app_namespace_t *app_ns;
-  application_t *app;
-  clib_socket_t *cs;
-  u32 cs_index;
-
-  app = application_get (app_wrk->app_index);
-  app_ns = app_namespace_get (app->ns_index);
-  cs_index = appns_sapi_handle_sock_index (app_wrk->api_client_index);
-  cs = appns_sapi_get_socket (app_ns, cs_index);
-  if (PREDICT_FALSE (!cs))
-    return;
-
-  /* There's no payload for the message only the type */
-  smsg.type = APP_SAPI_MSG_TYPE_SEND_FDS;
-  clib_socket_sendmsg (cs, &smsg, sizeof (smsg), fds, n_fds);
-}
-
 static int
 mq_send_add_segment_sapi_cb (u32 app_wrk_index, u64 segment_handle)
 {
-  int fds[SESSION_N_FD_TYPE], n_fds = 0;
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_app_add_segment_msg_t *mp;
+  session_app_add_segment_msg_t m = { 0 };
   app_worker_t *app_wrk;
-  session_event_t *evt;
-  svm_msg_q_t *app_mq;
   fifo_segment_t *fs;
   ssvm_private_t *sp;
   u8 fd_flags = 0;
@@ -1286,33 +1133,15 @@ mq_send_add_segment_sapi_cb (u32 app_wrk_index, u64 segment_handle)
   ASSERT (ssvm_type (sp) == SSVM_SEGMENT_MEMFD);
 
   fd_flags |= SESSION_FD_F_MEMFD_SEGMENT;
-  fds[n_fds] = sp->fd;
-  n_fds += 1;
-
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return -1;
 
-  /*
-   * Send the fd over api socket
-   */
-  sapi_send_fds (app_wrk, fds, n_fds);
+  m.segment_size = sp->ssvm_size;
+  m.fd_flags = fd_flags;
+  m.segment_handle = segment_handle;
+  strncpy ((char *) m.segment_name, (char *) sp->name,
+	   sizeof (m.segment_name) - 1);
 
-  /*
-   * Send the actual message over mq
-   */
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_APP_ADD_SEGMENT;
-  mp = (session_app_add_segment_msg_t *) evt->data;
-  clib_memset (mp, 0, sizeof (*mp));
-  mp->segment_size = sp->ssvm_size;
-  mp->fd_flags = fd_flags;
-  mp->segment_handle = segment_handle;
-  strncpy ((char *) mp->segment_name, (char *) sp->name,
-	   sizeof (mp->segment_name) - 1);
-
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt_fd (app_wrk, SESSION_CTRL_EVT_APP_ADD_SEGMENT, &m,
+			    sizeof (m), sp->fd);
 
   return 0;
 }
@@ -1320,25 +1149,15 @@ mq_send_add_segment_sapi_cb (u32 app_wrk_index, u64 segment_handle)
 static int
 mq_send_del_segment_sapi_cb (u32 app_wrk_index, u64 segment_handle)
 {
-  svm_msg_q_msg_t _msg, *msg = &_msg;
-  session_app_del_segment_msg_t *mp;
+  session_app_del_segment_msg_t m = { 0 };
   app_worker_t *app_wrk;
-  session_event_t *evt;
-  svm_msg_q_t *app_mq;
 
   app_wrk = app_worker_get (app_wrk_index);
 
-  app_mq = app_wrk->event_queue;
-  if (mq_try_lock_and_alloc_msg (app_mq, msg))
-    return -1;
+  m.segment_handle = segment_handle;
 
-  evt = svm_msg_q_msg_data (app_mq, msg);
-  clib_memset (evt, 0, sizeof (*evt));
-  evt->event_type = SESSION_CTRL_EVT_APP_DEL_SEGMENT;
-  mp = (session_app_del_segment_msg_t *) evt->data;
-  clib_memset (mp, 0, sizeof (*mp));
-  mp->segment_handle = segment_handle;
-  svm_msg_q_add_and_unlock (app_mq, msg);
+  app_wrk_send_ctrl_evt (app_wrk, SESSION_CTRL_EVT_APP_DEL_SEGMENT, &m,
+			 sizeof (m));
 
   return 0;
 }