From 209f5d32e198416b62ef18407dd04138a44bd4ad Mon Sep 17 00:00:00 2001
From: Evgeny Khramtsov <ekhramtsov@process-one.net>
Date: Tue, 30 Jul 2019 14:26:11 +0300
Subject: [PATCH] Fix SQL connections leakage

---
 src/ejabberd_sql.erl | 65 +++++++++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 31 deletions(-)

diff --git a/src/ejabberd_sql.erl b/src/ejabberd_sql.erl
index e0f1e9e10..b225a107a 100644
--- a/src/ejabberd_sql.erl
+++ b/src/ejabberd_sql.erl
@@ -343,31 +343,29 @@ connecting(connect, #state{host = Host} = State) ->
 		 end,
     case ConnectRes of
         {ok, Ref} ->
-            erlang:monitor(process, Ref),
-            lists:foreach(
-              fun({{?PREPARE_KEY, _} = Key, _}) ->
-                      erase(Key);
-                 (_) ->
-                      ok
-              end, get()),
-	    PendingRequests =
-		p1_queue:dropwhile(
-		  fun(Req) ->
-			  p1_fsm:send_event(self(), Req),
-			  true
-		  end, State#state.pending_requests),
-            State1 = State#state{db_ref = Ref,
-                                 pending_requests = PendingRequests},
-            State2 = get_db_version(State1),
-            {next_state, session_established, State2};
-      {error, Reason} ->
-	    StartInterval = ejabberd_option:sql_start_interval(Host),
-	    ?WARNING_MSG("~p connection failed:~n** Reason: ~p~n** "
-			 "Retry after: ~B seconds",
-			 [State#state.db_type, Reason,
-			  StartInterval div 1000]),
-	    p1_fsm:send_event_after(StartInterval, connect),
-	    {next_state, connecting, State}
+	    try link(Ref) of
+		_ ->
+		    lists:foreach(
+		      fun({{?PREPARE_KEY, _} = Key, _}) ->
+			      erase(Key);
+			 (_) ->
+			      ok
+		      end, get()),
+		    PendingRequests =
+			p1_queue:dropwhile(
+			  fun(Req) ->
+				  p1_fsm:send_event(self(), Req),
+				  true
+			  end, State#state.pending_requests),
+		    State1 = State#state{db_ref = Ref,
+					 pending_requests = PendingRequests},
+		    State2 = get_db_version(State1),
+		    {next_state, session_established, State2}
+	    catch _:Reason ->
+		    handle_reconnect(Reason, State)
+	    end;
+	{error, Reason} ->
+	    handle_reconnect(Reason, State)
     end;
 connecting(Event, State) ->
     ?WARNING_MSG("Unexpected event in 'connecting': ~p",
@@ -431,12 +429,8 @@ handle_sync_event(_Event, _From, StateName, State) ->
 code_change(_OldVsn, StateName, State, _Extra) ->
     {ok, StateName, State}.
 
-%% We receive the down signal when we loose the MySQL connection (we are
-%% monitoring the connection)
-handle_info({'DOWN', _MonitorRef, process, _Pid, _Info},
-	    _StateName, State) ->
-    p1_fsm:send_event(self(), connect),
-    {next_state, connecting, State};
+handle_info({'EXIT', _Pid, Reason}, _StateName, State) ->
+    handle_reconnect(Reason, State);
 handle_info(Info, StateName, State) ->
     ?WARNING_MSG("Unexpected info in ~p: ~p",
 		 [StateName, Info]),
@@ -460,6 +454,15 @@ print_state(State) -> State.
 %%%----------------------------------------------------------------------
 %%% Internal functions
 %%%----------------------------------------------------------------------
+handle_reconnect(Reason, #state{host = Host} = State) ->
+    StartInterval = ejabberd_option:sql_start_interval(Host),
+    ?WARNING_MSG("~p connection failed:~n"
+		 "** Reason: ~p~n"
+		 "** Retry after: ~B seconds",
+		 [State#state.db_type, Reason,
+		  StartInterval div 1000]),
+    p1_fsm:send_event_after(StartInterval, connect),
+    {next_state, connecting, State}.
 
 run_sql_cmd(Command, From, State, Timestamp) ->
     QueryTimeout = query_timeout(State#state.host),