Remove shared counters and use simple properties

lib/poxa/presence_subscription.ex

@@ -26,14 +26,12 @@ defmodule Poxa.PresenceSubscription do
     else
       Lager.info('Registering ~p to channel ~p', [self, channel])
       {user_id, user_info} = extract_userid_and_userinfo(decoded_channel_data)
-      if user_id_already_on_presence_channel(user_id, channel) do
-        :gproc.update_shared_counter({:c, :l, {:presence, channel, user_id}}, 1)
-      else
+      unless user_id_already_on_presence_channel(user_id, channel) do
         message = PusherEvent.presence_member_added(channel, user_id, user_info)
-        :gproc.add_shared_local_counter({:presence, channel, user_id}, 1)
         :gproc.send({:p, :l, {:pusher, channel}}, {self, message})
       end
-      :gproc.reg({:p, :l, {:pusher, channel}}, {user_id, user_info})
+      :gproc.mreg(:p, :l, [{{:pusher, channel}, {user_id, user_info}},
+                           {{:presence, channel, user_id}, user_info}])
     end
     {:presence, channel, :gproc.lookup_values({:p, :l, {:pusher, channel}})}
   end
@@ -44,6 +42,11 @@ defmodule Poxa.PresenceSubscription do
     {user_id, user_info}
   end
 
+  defp user_id_already_on_presence_channel(user_id, channel) do
+    match = {{:p, :l, {:presence, channel, user_id}}, :_, :_}
+    :gproc.select_count([{match, [], [true]}]) != 0
+  end
+
   @spec unsubscribe!(binary) :: :ok
   def unsubscribe!(channel) do
     case :gproc.get_value({:p, :l, {:pusher, channel}}) do
@@ -93,22 +96,22 @@ defmodule Poxa.PresenceSubscription do
     member_remove_fun = fn([channel, user_id]) ->
       if presence_channel?(channel) do
         if only_one_connection_on_user_id?(channel, user_id) do
-          :gproc.unreg_shared({:c, :l, {:presence, channel, user_id}})
           message = PusherEvent.presence_member_removed(channel, user_id)
           :gproc.send({:p, :l, {:pusher, channel}}, {self, message})
-        else
-          :gproc.update_shared_counter({:c, :l, {:presence, channel, user_id}}, -1)
         end
       end
     end
     Enum.each(channel_user_id, member_remove_fun)
     :ok
   end
 
-  @spec presence_channel?(any) :: boolean
-  def presence_channel?("presence-" <> _presence_channel  = _channel) do
-    true
+  defp only_one_connection_on_user_id?(channel, user_id) do
+    match = {{:p, :l, {:presence, channel, user_id}}, :_, :_}
+    :gproc.select_count([{match, [], [true]}]) == 1
   end
+
+  @spec presence_channel?(any) :: boolean
+  def presence_channel?("presence-" <> _  = _channel), do:  true
   def presence_channel?(_), do: false
 
   defp sanitize_user_id(user_id) do
@@ -117,23 +120,4 @@ defmodule Poxa.PresenceSubscription do
       false -> user_id
     end
   end
-
-  defp user_id_already_on_presence_channel(user_id, channel) do
-    match = {{:p, :l, {:pusher, channel}}, :_, {user_id, :_}}
-    case :gproc.select([{match, [], [:'$$']}]) do
-      [] -> false
-      _ -> true
-    end
-  end
-
-  defp only_one_connection_on_user_id?(channel, user_id) do
-    try do
-      case :gproc.get_value({:c, :l, {:presence, channel, user_id}}, :shared) do
-        1 -> true
-        _ -> false
-      end
-    rescue
-      ArgumentError -> false
-    end
-  end
 end

test/presence_subscription_test.exs

@@ -21,10 +21,9 @@ defmodule Poxa.PresenceSubscriptionTest do
 
   test "subscribe to a presence channel" do
     expect(Subscription, :subscribed?, 1, false)
-    expect(:gproc, :select, 1, []) # false for user_id_already_on_presence_channel/2
-    expect(:gproc, :add_shared_local_counter, 2, :ok)
+    expect(:gproc, :select_count, 1, 0)
     expect(:gproc, :send, 2, :sent)
-    expect(:gproc, :reg, 2, :registered)
+    expect(:gproc, :mreg, 3, :registered)
     expect(PusherEvent, :presence_member_added, 3, :event_message)
     expect(:gproc, :lookup_values, 1, :values)
     assert subscribe!("presence-channel", "{ \"user_id\" : \"id123\", \"user_info\" : \"info456\" }") == {:presence, "presence-channel", :values}
@@ -44,9 +43,9 @@ defmodule Poxa.PresenceSubscriptionTest do
 
   test "subscribe to a presence channel having the same userid" do
     expect(Subscription, :subscribed?, 1, false)
-    expect(:gproc, :select, 1, [:something]) # true for user_id_already_on_presence_channel/2
+    expect(:gproc, :select_count, 1, 1) # true for user_id_already_on_presence_channel/2
     expect(:gproc, :update_shared_counter, 2, :ok)
-    expect(:gproc, :reg, 2, :registered)
+    expect(:gproc, :mreg, 3, :registered)
     expect(:gproc, :lookup_values, 1, :values)
     assert subscribe!("presence-channel", "{ \"user_id\" : \"id123\", \"user_info\" : \"info456\" }") == {:presence, "presence-channel", :values}
     assert validate Subscription
@@ -71,8 +70,7 @@ defmodule Poxa.PresenceSubscriptionTest do
 
   test "check subscribed presence channels and remove having only one connection on userid" do
     expect(:gproc, :select, 1, [["presence-channel", :userid]])
-    expect(:gproc, :get_value, 2, 1)
-    expect(:gproc, :unreg_shared, 1, :ok)
+    expect(:gproc, :select_count, 1, 1)
     expect(PusherEvent, :presence_member_removed, 2, :msg)
     expect(:gproc, :send, 2, :ok)
     assert check_and_remove == :ok
@@ -82,8 +80,7 @@ defmodule Poxa.PresenceSubscriptionTest do
 
   test "check subscribed presence channels and remove having more than one connection on userid" do
     expect(:gproc, :select, 1, [["presence-channel", :userid]])
-    expect(:gproc, :get_value, 2, 5)
-    expect(:gproc, :update_shared_counter, 2, :ok)
+    expect(:gproc, :select_count, 1, 5)
     assert check_and_remove == :ok
     assert validate PusherEvent
     assert validate :gproc