From 47ae6a42179188cb79acf17ed71ce85343dcb629 Mon Sep 17 00:00:00 2001
From: Chandrashekhar Mullaparthi <chandrashekhar.mullaparthi@gmail.com>
Date: Fri, 8 Aug 2014 15:46:50 +0100
Subject: [PATCH] More fixes to pipelining

---
 src/ibrowse_lb.erl | 84 ++++++++++++++++++----------------------------
 1 file changed, 33 insertions(+), 51 deletions(-)

diff --git a/src/ibrowse_lb.erl b/src/ibrowse_lb.erl
index 2b34ddb..a802f87 100644
--- a/src/ibrowse_lb.erl
+++ b/src/ibrowse_lb.erl
@@ -36,7 +36,6 @@
 		port,
 		max_sessions,
 		max_pipeline_size,
-		num_cur_sessions = 0,
                 proc_state
                }).
 
@@ -123,24 +122,23 @@ handle_call(stop, _From, #state{ets_tid = Tid} = State) ->
 handle_call(_, _From, #state{proc_state = shutting_down} = State) ->
     {reply, {error, shutting_down}, State};
 
-%% Update max_sessions in #state with supplied value
-handle_call({spawn_connection, _Url, Max_sess, Max_pipe, _, _}, _From,
-	    #state{num_cur_sessions = Num} = State)
-    when Num >= Max_sess ->
-    State_1 = maybe_create_ets(State),
-    Reply = find_best_connection(State_1#state.ets_tid, Max_pipe),
-    {reply, Reply, State_1#state{max_sessions = Max_sess,
-                                 max_pipeline_size = Max_pipe}};
-
 handle_call({spawn_connection, Url, Max_sess, Max_pipe, SSL_options, Process_options}, _From,
-	    #state{num_cur_sessions = Cur} = State) ->
-    State_1 = maybe_create_ets(State),
-    Tid = State_1#state.ets_tid,
-    {ok, Pid} = ibrowse_http_client:start_link({Tid, Url, SSL_options}, Process_options),
-    ets:insert(Tid, {{0, Pid}, []}),
-    {reply, {ok, Pid}, State_1#state{num_cur_sessions = Cur + 1,
-                                     max_sessions = Max_sess,
-                                     max_pipeline_size = Max_pipe}};
+	    State) ->
+    State_1   = maybe_create_ets(State),
+    Tid       = State_1#state.ets_tid,
+    Tid_size  = ets:info(Tid, size),
+    case Tid_size > Max_sess of
+        true ->
+            Reply = find_best_connection(Tid, Max_pipe, Tid_size),
+            {reply, Reply, State_1#state{max_sessions      = Max_sess,
+                                         max_pipeline_size = Max_pipe}};
+        false ->
+            {ok, Pid} = ibrowse_http_client:start({Tid, Url, SSL_options}, Process_options),
+            Ts = os:timestamp(),
+            ets:insert(Tid, {{0, Ts, Pid}, []}),
+            {reply, {ok, {0, Ts, Pid}}, State_1#state{max_sessions      = Max_sess,
+                                                  max_pipeline_size = Max_pipe}}
+    end;
 
 handle_call(Request, _From, State) ->
     Reply = {unknown_request, Request},
@@ -163,24 +161,6 @@ handle_cast(_Msg, State) ->
 %%          {noreply, State, Timeout} |
 %%          {stop, Reason, State}            (terminate/2 is called)
 %%--------------------------------------------------------------------
-handle_info({'EXIT', Parent, _Reason}, #state{parent_pid = Parent} = State) ->
-    {stop, normal, State};
-
-handle_info({'EXIT', _Pid, _Reason}, #state{ets_tid = undefined} = State) ->
-    {noreply, State};
-
-handle_info({'EXIT', Pid, _Reason},
-	    #state{num_cur_sessions = Cur,
-		   ets_tid = Tid} = State) ->
-    ets:match_delete(Tid, {{'_', Pid}, '_'}),
-    Cur_1 = Cur - 1,
-    case Cur_1 of
-		  0 ->
-		      ets:delete(Tid),
-			  {noreply, State#state{ets_tid = undefined, num_cur_sessions = 0}, 10000};
-		  _ ->
-		      {noreply, State#state{num_cur_sessions = Cur_1}}
-	      end;
 
 handle_info({trace, Bool}, #state{ets_tid = undefined} = State) ->
     put(my_trace_flag, Bool),
@@ -216,7 +196,8 @@ handle_info(_Info, State) ->
 %% Description: Shutdown the server
 %% Returns: any (ignored by gen_server)
 %%--------------------------------------------------------------------
-terminate(_Reason, _State) ->
+terminate(_Reason, #state{host = Host, port = Port} = _State) ->
+    catch ets:delete(ibrowse_lb, {Host, Port}),
     ok.
 
 %%--------------------------------------------------------------------
@@ -230,23 +211,24 @@ code_change(_OldVsn, State, _Extra) ->
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------
-find_best_connection(Tid, Max_pipe) ->
-    First = ets:first(Tid),
-    case First of
-        {Pid_pipeline_size, Pid} when Pid_pipeline_size < Max_pipe ->
-            ets:delete(Tid, First),
-            ets:insert(Tid, {{Pid_pipeline_size, Pid}, []}),
-            {ok, Pid};
-        _ ->
-           {error, retry_later}
+find_best_connection(Tid, Max_pipe, _Num_cur) ->
+    case ets:first(Tid) of
+        {Spec_size, Ts, Pid} = First ->
+            case Spec_size >= Max_pipe of
+                true ->
+                    {error, retry_later};
+                false ->
+                    ets:delete(Tid, First),
+                    ets:insert(Tid, {{Spec_size + 1, Ts, Pid}, []}),
+                    {ok, First}
+            end;
+        '$end_of_table' ->
+            {error, retry_later}
     end.
 
-maybe_create_ets(#state{ets_tid = undefined,
-                        host = Host, port = Port} = State) ->
+maybe_create_ets(#state{ets_tid = undefined, host = Host, port = Port} = State) ->
     Tid = ets:new(ibrowse_lb, [public, ordered_set]),
-    ets:insert(ibrowse_lb, #lb_pid{host_port = {Host, Port},
-                                   pid = self(),
-                                   ets_tid = Tid}),
+    ets:insert(ibrowse_lb, #lb_pid{host_port = {Host, Port}, pid = self(), ets_tid = Tid}),
     State#state{ets_tid = Tid};
 maybe_create_ets(State) ->
     State.