From 058b018e5cf5dcd330d094dc42e623b099dfbcad Mon Sep 17 00:00:00 2001
From: Zaiming Shi <zmstone@gmail.com>
Date: Sun, 11 Apr 2021 12:46:25 +0200
Subject: [PATCH] chore(build): optional observer release

---
 rebar.config.erl | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/rebar.config.erl b/rebar.config.erl
index cce629868..1fb421a49 100644
--- a/rebar.config.erl
+++ b/rebar.config.erl
@@ -239,13 +239,20 @@ relx_apps(ReleaseType) ->
     ++ [{N, load} || N <- relx_plugin_apps(ReleaseType)].
 
 relx_apps_per_rel(cloud) ->
-    [ {observer, load}
-    , luerl
+    [ luerl
     , xmerl
+    | [{observer, load} || is_app(observer)]
     ];
 relx_apps_per_rel(edge) ->
     [].
 
+is_app(Name) ->
+    case application:load(Name) of
+        ok -> true;
+        {error,{already_loaded, _}} -> true;
+        _ -> false
+    end.
+
 relx_plugin_apps(ReleaseType) ->
     [ emqx_retainer
     , emqx_management