increase reliability of sessions

lib/floof.ex

@@ -79,8 +79,7 @@ defmodule Floof do
             end
 
           {:ok, dcd} = :FloofProtocol.decode(:ProtoMessage, message)
-          backlog = handle_incoming(client, backlog, sesskey, dcd)
-          {backlog, sesskey}
+          handle_incoming(client, backlog, sesskey, dcd)
 
         {:fwdxfer, {dcdhash, dcd}} ->
           backlog =
@@ -99,8 +98,15 @@ defmodule Floof do
           :ok = send_summary(client, :requestpull, Floof.SessionManager.peek(sesskey))
           {backlog, sesskey}
 
-        {:SessionDetached, _} ->
-          {backlog, nil}
+        {:SessionDetached, old_sesskey} ->
+          sesskey2 =
+            if sesskey == old_sesskey do
+              nil
+            else
+              sesskey
+            end
+
+          {backlog, sesskey2}
 
         {:tcp_closed, _} ->
           # put all the backlogged stuff back if possible
@@ -123,10 +129,14 @@ defmodule Floof do
     Logger.debug("got packet #{inspect(dcd)}")
 
     case dcd do
-      {:session, {:attach, sesskey}} ->
-        Floof.SessionManager.attach(sesskey, self())
-        transfer_backlog_to_session(sesskey, backlog)
-        %{}
+      {:session, {:attach, sesskey_new}} ->
+        if sesskey != nil do
+          Floof.SessionManager.detach(sesskey, self())
+        end
+
+        Floof.SessionManager.attach(sesskey_new, self())
+        transfer_backlog_to_session(sesskey_new, backlog)
+        {%{}, sesskey_new}
 
       {:summary, {:Summary, direction, hashes}} ->
         case direction do
@@ -134,7 +144,7 @@ defmodule Floof do
             {to_pull, to_drop} = partition_hashes(hashes)
             :ok = send_summary(client, :pull, to_pull)
             :ok = send_summary(client, :drop, to_drop)
-            backlog
+            {backlog, sesskey}
 
           :pull ->
             for mhash <- hashes do
@@ -154,14 +164,14 @@ defmodule Floof do
               end
             end
 
-            backlog
+            {backlog, sesskey}
 
           :drop ->
             if sesskey != nil do
               Floof.SessionManager.drop(sesskey, hashes)
             end
 
-            Map.drop(backlog, hashes)
+            {Map.drop(backlog, hashes), sesskey}
         end
 
       {:xfer, xf} ->
@@ -169,7 +179,7 @@ defmodule Floof do
         # notify the remote end that we successfully consumed the message
         # non-fatal if this fails
         send_summary(client, :drop, [mhash])
-        backlog
+        {backlog, sesskey}
     end
   end
 
@@ -185,7 +195,7 @@ defmodule Floof do
 
   defp transfer_backlog_to_session(sesskey, backlog) do
     Floof.SessionManager.set_soft_multi(sesskey, for({dcdhash, _} <- backlog, do: dcdhash))
-    Floof.PacketSpool.store_new_multi(backlog)
+    :ok = Floof.PacketSpool.store_new_multi(backlog)
   end
 
   defp partition_hashes(xs) do