[couchdb] branch master updated: Make couch_event_sup:stop/1 synchronous

[va...@apache.org]

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vatamane pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/couchdb.git


The following commit(s) were added to refs/heads/master by this push:
     new cc668ba  Make couch_event_sup:stop/1 synchronous
cc668ba is described below

commit cc668ba7b67b27369720fa3b9cac6844c698f1a0
Author: Nick Vatamaniuc <va...@apache.org>
AuthorDate: Tue Jul 11 10:43:28 2017 -0400

    Make couch_event_sup:stop/1 synchronous
    
    Because `stop/1` is asynchronous, and casts a stop message and as result the
    client process could end getting killed during termination/cleanup phase if
    this sequence of events took place:
    
    1. Client calls `stop(ListerPid).`
    
    2. couch_event_sup casts a `stop` message to couch_event_sup gen_server
    
    3. `stop` message is delayed and client continues executing.
    
    4. Client calls something like application:stop/1`.
    
    5. `application:stop/1` terminates couch_event_sup gen_server.
    
    6. App termination kills client process because it is still linked.
    
    So this make the stop synchrounous by using call instead of cast.
    
    Issue #644
---
 src/couch/src/couch_event_sup.erl | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/couch/src/couch_event_sup.erl b/src/couch/src/couch_event_sup.erl
index b617498..32f1b9b 100644
--- a/src/couch/src/couch_event_sup.erl
+++ b/src/couch/src/couch_event_sup.erl
@@ -48,7 +48,7 @@ start_link(ServerName, EventMgr, EventHandler, Args) ->
     gen_server:start_link(ServerName, couch_event_sup, {EventMgr, EventHandler, Args}, []).
 
 stop(Pid) ->
-    gen_server:cast(Pid, stop).
+    gen_server:call(Pid, stop).
 
 init({EventMgr, EventHandler, Args}) ->
     case gen_event:add_sup_handler(EventMgr, EventHandler, Args) of
@@ -61,11 +61,11 @@ init({EventMgr, EventHandler, Args}) ->
 terminate(_Reason, _State) ->
     ok.
 
-handle_call(_Whatever, _From, State) ->
-    {reply, ok, State}.
+handle_call(stop, _From, State) ->
+    {stop, normal, ok, State}.
 
-handle_cast(stop, State) ->
-    {stop, normal, State}.
+handle_cast(_Msg, State) ->
+    {noreply, State}.
 
 handle_info({gen_event_EXIT, _Handler, Reason}, State) ->
     {stop, Reason, State}.

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