From f0f1456168303c4298e308bb146e5e81ffb9c2f7 Mon Sep 17 00:00:00 2001
From: Gilbert Wong <gilbertwong96@icloud.com>
Date: Mon, 27 Aug 2018 11:21:16 +0800
Subject: [PATCH] fix duplicated subscribers with same topic

---
 src/emqx_broker.erl | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/emqx_broker.erl b/src/emqx_broker.erl
index 8fed40b7f..560c095cf 100644
--- a/src/emqx_broker.erl
+++ b/src/emqx_broker.erl
@@ -379,9 +379,18 @@ code_change(_OldVsn, State, _Extra) ->
 %% Internal functions
 %%------------------------------------------------------------------------------
 
+insert_subscriber(Group, Topic, Subscriber) ->
+    Subscribers = subscribers(Topic),
+    case lists:member(Subscriber, Subscribers) of
+        false ->
+            ets:insert(?SUBSCRIBER, {Topic, shared(Group, Subscriber)});
+        _ ->
+            ok
+    end.
+
 do_subscribe(Group, Topic, Subscriber, SubOpts) ->
     ets:insert(?SUBSCRIPTION, {Subscriber, shared(Group, Topic)}),
-    ets:insert(?SUBSCRIBER, {Topic, shared(Group, Subscriber)}),
+    insert_subscriber(Group, Topic, Subscriber),
     ets:insert(?SUBOPTION, {{Topic, Subscriber}, SubOpts}).
 
 do_unsubscribe(Group, Topic, Subscriber) ->