X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fvnet%2Fsession%2Fapplication_worker.c;h=c3941d1fd7b3aa4e83159d721e06a16e5a6541e9;hb=0028e6f31624246e831b5b1a13dc46ab1d864fa7;hp=dd159c6693cf8a15a0e503384ac3a923c091dfca;hpb=e655240550f0670279b0ca40942887715b8f514e;p=vpp.git

diff --git a/src/vnet/session/application_worker.c b/src/vnet/session/application_worker.c
index dd159c6693c..c3941d1fd7b 100644
--- a/src/vnet/session/application_worker.c
+++ b/src/vnet/session/application_worker.c
@@ -32,8 +32,8 @@ app_worker_alloc (application_t * app)
   app_wrk->app_index = app->app_index;
   app_wrk->wrk_map_index = ~0;
   app_wrk->connects_seg_manager = APP_INVALID_SEGMENT_MANAGER_INDEX;
-  app_wrk->first_segment_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;
 }
@@ -59,9 +59,10 @@ app_worker_free (app_worker_t * app_wrk)
   vnet_unlisten_args_t _a, *a = &_a;
   u64 handle, *handles = 0, *sm_indices = 0;
   segment_manager_t *sm;
+  session_handle_t *sh;
   session_t *ls;
   u32 sm_index;
-  int i, j;
+  int i;
 
   /*
    *  Listener cleanup
@@ -111,26 +112,10 @@ app_worker_free (app_worker_t * app_wrk)
    * Half-open cleanup
    */
 
-  for (i = 0; i < vec_len (app_wrk->half_open_table); i++)
-    {
-      if (!app_wrk->half_open_table[i])
-	continue;
-
-      /* *INDENT-OFF* */
-      hash_foreach (handle, sm_index, app_wrk->half_open_table[i], ({
-	vec_add1 (handles, handle);
-      }));
-      /* *INDENT-ON* */
-
-      for (j = 0; j < vec_len (handles); j++)
-	session_cleanup_half_open (i, handles[j]);
+  pool_foreach (sh, app_wrk->half_open_table)
+    session_cleanup_half_open (*sh);
 
-      hash_free (app_wrk->half_open_table[i]);
-      vec_reset_length (handles);
-    }
-
-  vec_free (app_wrk->half_open_table);
-  vec_free (handles);
+  pool_free (app_wrk->half_open_table);
 
   /*
    * Detached listener segment managers cleanup
@@ -142,17 +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);
-
-  /* If first segment manager is used by a listener that recently
-   * stopped listening, mark it as detached */
-  if (app_wrk->first_segment_manager != app_wrk->connects_seg_manager
-      && (sm = segment_manager_get_if_valid (app_wrk->first_segment_manager))
-      && !segment_manager_app_detached (sm))
-    {
-      sm->first_is_protected = 0;
-      sm->app_wrk_index = SEGMENT_MANAGER_INVALID_APP_INDEX;
-      segment_manager_init_free (sm);
-    }
+  clib_spinlock_free (&app_wrk->postponed_mq_msgs_lock);
 
   if (CLIB_DEBUG)
     clib_memset (app_wrk, 0xfe, sizeof (*app_wrk));
@@ -172,19 +147,9 @@ app_worker_get_app (u32 wrk_index)
 static segment_manager_t *
 app_worker_alloc_segment_manager (app_worker_t * app_wrk)
 {
-  segment_manager_t *sm = 0;
+  segment_manager_t *sm;
 
-  /* If the first segment manager is not in use, don't allocate a new one */
-  if (app_wrk->first_segment_manager != APP_INVALID_SEGMENT_MANAGER_INDEX
-      && app_wrk->first_segment_manager_in_use == 0)
-    {
-      sm = segment_manager_get (app_wrk->first_segment_manager);
-      app_wrk->first_segment_manager_in_use = 1;
-    }
-  else
-    {
-      sm = segment_manager_alloc ();
-    }
+  sm = segment_manager_alloc ();
   sm->app_wrk_index = app_wrk->wrk_index;
   segment_manager_init (sm);
   return sm;
@@ -200,10 +165,10 @@ app_worker_alloc_session_fifos (segment_manager_t * sm, session_t * s)
 						 &rx_fifo, &tx_fifo)))
     return rv;
 
-  rx_fifo->master_session_index = s->session_index;
+  rx_fifo->shr->master_session_index = s->session_index;
   rx_fifo->master_thread_index = s->thread_index;
 
-  tx_fifo->master_session_index = s->session_index;
+  tx_fifo->shr->master_session_index = s->session_index;
   tx_fifo->master_thread_index = s->thread_index;
 
   s->rx_fifo = rx_fifo;
@@ -221,6 +186,9 @@ app_worker_init_listener (app_worker_t * app_wrk, session_t * ls)
   if (!(sm = app_worker_alloc_segment_manager (app_wrk)))
     return SESSION_E_ALLOC;
 
+  /* Once the first segment is mapped, don't remove it until unlisten */
+  sm->first_is_protected = 1;
+
   /* Keep track of the segment manager for the listener or this worker */
   hash_set (app_wrk->listeners_table, listen_session_get_handle (ls),
 	    segment_manager_index (sm));
@@ -234,9 +202,8 @@ app_worker_init_listener (app_worker_t * app_wrk, session_t * ls)
   return 0;
 }
 
-int
-app_worker_start_listen (app_worker_t * app_wrk,
-			 app_listener_t * app_listener)
+session_error_t
+app_worker_start_listen (app_worker_t *app_wrk, app_listener_t *app_listener)
 {
   session_t *ls;
   int rv;
@@ -293,6 +260,7 @@ app_worker_stop_listen_session (app_worker_t * app_wrk, session_t * ls)
   session_handle_t handle;
   segment_manager_t *sm;
   uword *sm_indexp;
+  session_state_t *states = 0;
 
   handle = listen_session_get_handle (ls);
   sm_indexp = hash_get (app_wrk->listeners_table, handle);
@@ -308,13 +276,22 @@ app_worker_stop_listen_session (app_worker_t * app_wrk, session_t * ls)
 
   /* Try to cleanup segment manager */
   sm = segment_manager_get (*sm_indexp);
-  if (sm && app_wrk->first_segment_manager != *sm_indexp)
+  if (sm)
     {
+      sm->first_is_protected = 0;
       segment_manager_app_detach (sm);
       if (!segment_manager_has_fifos (sm))
-	segment_manager_free (sm);
+	{
+	  /* Empty segment manager, cleanup it up */
+	  segment_manager_free (sm);
+	}
       else
 	{
+	  /* Delete sessions in CREATED state */
+	  vec_add1 (states, SESSION_STATE_CREATED);
+	  segment_manager_del_sessions_filter (sm, states);
+	  vec_free (states);
+
 	  /* Track segment manager in case app detaches and all the
 	   * outstanding sessions need to be closed */
 	  app_worker_add_detached_sm (app_wrk, *sm_indexp);
@@ -362,8 +339,10 @@ 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;
@@ -409,39 +388,28 @@ app_worker_connect_notify (app_worker_t * app_wrk, session_t * s,
 }
 
 int
-app_worker_add_half_open (app_worker_t * app_wrk, transport_proto_t tp,
-			  session_handle_t ho_handle,
-			  session_handle_t wrk_handle)
+app_worker_add_half_open (app_worker_t *app_wrk, session_handle_t sh)
 {
-  ASSERT (vlib_get_thread_index () == 0);
-  vec_validate (app_wrk->half_open_table, tp);
-  hash_set (app_wrk->half_open_table[tp], ho_handle, wrk_handle);
-  return 0;
+  session_handle_t *shp;
+
+  ASSERT (session_vlib_thread_is_cl_thread ());
+  pool_get (app_wrk->half_open_table, shp);
+  *shp = sh;
+
+  return (shp - app_wrk->half_open_table);
 }
 
 int
-app_worker_del_half_open (app_worker_t * app_wrk, transport_proto_t tp,
-			  session_handle_t ho_handle)
+app_worker_del_half_open (app_worker_t *app_wrk, session_t *s)
 {
-  ASSERT (vlib_get_thread_index () == 0);
-  hash_unset (app_wrk->half_open_table[tp], ho_handle);
+  application_t *app = application_get (app_wrk->app_index);
+  ASSERT (session_vlib_thread_is_cl_thread ());
+  pool_put_index (app_wrk->half_open_table, s->ho_index);
+  if (app->cb_fns.half_open_cleanup_callback)
+    app->cb_fns.half_open_cleanup_callback (s);
   return 0;
 }
 
-u64
-app_worker_lookup_half_open (app_worker_t * app_wrk, transport_proto_t tp,
-			     session_handle_t ho_handle)
-{
-  u64 *ho_wrk_handlep;
-
-  /* No locking because all updates are done from main thread */
-  ho_wrk_handlep = hash_get (app_wrk->half_open_table[tp], ho_handle);
-  if (!ho_wrk_handlep)
-    return SESSION_INVALID_HANDLE;
-
-  return *ho_wrk_handlep;
-}
-
 int
 app_worker_close_notify (app_worker_t * app_wrk, session_t * s)
 {
@@ -511,6 +479,7 @@ app_worker_own_session (app_worker_t * app_wrk, session_t * s)
 {
   segment_manager_t *sm;
   svm_fifo_t *rxf, *txf;
+  int rv;
 
   if (s->session_state == SESSION_STATE_LISTENING)
     return application_change_listener_owner (s, app_wrk);
@@ -526,9 +495,9 @@ app_worker_own_session (app_worker_t * app_wrk, session_t * s)
   s->rx_fifo = 0;
   s->tx_fifo = 0;
 
-  sm = app_worker_get_or_alloc_connect_segment_manager (app_wrk);
-  if (app_worker_alloc_session_fifos (sm, s))
-    return -1;
+  sm = app_worker_get_connect_segment_manager (app_wrk);
+  if ((rv = app_worker_alloc_session_fifos (sm, s)))
+    return rv;
 
   if (!svm_fifo_is_empty_cons (rxf))
     svm_fifo_clone (s->rx_fifo, rxf);
@@ -542,19 +511,15 @@ app_worker_own_session (app_worker_t * app_wrk, session_t * s)
 }
 
 int
-app_worker_connect_session (app_worker_t * app_wrk, session_endpoint_t * sep,
-			    u32 api_context)
+app_worker_connect_session (app_worker_t *app_wrk, session_endpoint_cfg_t *sep,
+			    session_handle_t *rsh)
 {
-  int rv;
+  if (PREDICT_FALSE (app_wrk->mq_congested))
+    return SESSION_E_REFUSED;
 
-  /* Make sure we have a segment manager for connects */
-  if (app_worker_alloc_connects_segment_manager (app_wrk))
-    return SESSION_E_ALLOC;
-
-  if ((rv = session_open (app_wrk->wrk_index, sep, api_context)))
-    return rv;
+  sep->app_wrk_index = app_wrk->wrk_index;
 
-  return 0;
+  return session_open (sep, rsh);
 }
 
 int
@@ -566,21 +531,6 @@ app_worker_session_fifo_tuning (app_worker_t * app_wrk, session_t * s,
   return app->cb_fns.fifo_tuning_callback (s, f, act, len);
 }
 
-int
-app_worker_alloc_connects_segment_manager (app_worker_t * app_wrk)
-{
-  segment_manager_t *sm;
-
-  if (app_wrk->connects_seg_manager == APP_INVALID_SEGMENT_MANAGER_INDEX)
-    {
-      sm = app_worker_alloc_segment_manager (app_wrk);
-      if (sm == 0)
-	return -1;
-      app_wrk->connects_seg_manager = segment_manager_index (sm);
-    }
-  return 0;
-}
-
 segment_manager_t *
 app_worker_get_connect_segment_manager (app_worker_t * app)
 {
@@ -588,14 +538,6 @@ app_worker_get_connect_segment_manager (app_worker_t * app)
   return segment_manager_get (app->connects_seg_manager);
 }
 
-segment_manager_t *
-app_worker_get_or_alloc_connect_segment_manager (app_worker_t * app_wrk)
-{
-  if (app_wrk->connects_seg_manager == (u32) ~ 0)
-    app_worker_alloc_connects_segment_manager (app_wrk);
-  return segment_manager_get (app_wrk->connects_seg_manager);
-}
-
 segment_manager_t *
 app_worker_get_listen_segment_manager (app_worker_t * app,
 				       session_t * listener)
@@ -679,12 +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 < 75)
+    {
+      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);
@@ -692,68 +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);
+
+  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->session_index = s->rx_fifo->client_session_index;
+  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->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* */
@@ -792,10 +966,12 @@ format_app_worker_listener (u8 * s, va_list * args)
   if (!app_wrk)
     {
       if (verbose)
-	s = format (s, "%-40s%-25s%-10s%-15s%-15s%-10s", "Connection", "App",
-		    "Wrk", "API Client", "ListenerID", "SegManager");
+	s = format (s, "%-" SESSION_CLI_ID_LEN "s%-25s%-10s%-15s%-15s%-10s",
+		    "Connection", "App", "Wrk", "API Client", "ListenerID",
+		    "SegManager");
       else
-	s = format (s, "%-40s%-25s%-10s", "Connection", "App", "Wrk");
+	s = format (s, "%-" SESSION_CLI_ID_LEN "s%-25s%-10s", "Connection",
+		    "App", "Wrk");
 
       return s;
     }
@@ -808,12 +984,13 @@ format_app_worker_listener (u8 * s, va_list * args)
     {
       u8 *buf;
       buf = format (0, "%u(%u)", app_wrk->wrk_map_index, app_wrk->wrk_index);
-      s = format (s, "%-40v%-25v%-10v%-15u%-15u%-10u", str, app_name,
-		  buf, app_wrk->api_client_index, handle, sm_index);
+      s = format (s, "%-" SESSION_CLI_ID_LEN "v%-25v%-10v%-15u%-15u%-10u", str,
+		  app_name, buf, app_wrk->api_client_index, handle, sm_index);
       vec_free (buf);
     }
   else
-    s = format (s, "%-40v%-25v%=10u", str, app_name, app_wrk->wrk_map_index);
+    s = format (s, "%-" SESSION_CLI_ID_LEN "v%-25v%=10u", str, app_name,
+		app_wrk->wrk_map_index);
 
   vec_free (str);
 
@@ -826,10 +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;
 }