fix: cluster crash

apps/emqx/src/emqx_metrics.erl

@@ -337,12 +337,18 @@ all() ->
 %% @doc Get metric value
 -spec val(metric_name()) -> non_neg_integer().
 val(Name) ->
+    try
         case ets:lookup(?TAB, Name) of
             [#metric{idx = Idx}] ->
                 CRef = persistent_term:get(?MODULE),
                 counters:get(CRef, Idx);
             [] ->
                 0
+        end
+        %% application will restart when join cluster, then ets not exist.
+    catch
+        error:badarg ->
+            0
     end.
 
 %% @doc Increase counter

apps/emqx_conf/etc/emqx_conf.conf

@@ -13,6 +13,7 @@ node {
   cookie: emqxsecretcookie
   data_dir: "{{ platform_data_dir }}"
   etc_dir: "{{ platform_etc_dir }}"
+  applications: "{{ emqx_machine_boot_apps }}"
 }
 
 log {