docs: Update thread communication docs

docs/_static/thread_communication.txt

@@ -1,37 +1,37 @@
 Script for use with www.websequencediagrams.com
 ===============================================
 
-Main -> NadMixer: start
+Main -> Core: create
-activate NadMixer
+activate Core
-note over NadMixer: calibrate device
+note over Core: create NadMixer
-NadMixer -> Main: ready
+Core -> NadTalker: create
-Main -> MpdHandler/Backend: start
+activate NadTalker
-activate MpdHandler/Backend
+note over NadTalker: calibrate device
-MpdHandler/Backend -> despotify: connect to Spotify
+note over Core: create DespotifyBackend
+Core -> despotify: connect to Spotify
 activate despotify
-MpdHandler/Backend -> Main: ready
+note over Core: create MpdFrontend
-Main -> MpdServer/MpdSession: start
+Main -> Server: create
-activate MpdServer/MpdSession
+activate Server
-note over MpdServer/MpdSession: open port
+note over Server: open port
-MpdServer/MpdSession -> Main: ready
+Client -> Server: connect
-Client -> MpdServer/MpdSession: connect
+note over Server: open session
-note over MpdServer/MpdSession: open session
+Client -> Server: play 1
-Client -> MpdServer/MpdSession: play 1
+Server -> Core: play 1
-MpdServer/MpdSession -> MpdHandler/Backend: play 1
+Core -> despotify: play first track
-MpdHandler/Backend -> despotify: play first track
+Client -> Server: setvol 50
-Client -> MpdServer/MpdSession: setvol 50
+Server -> Core: setvol 50
-MpdServer/MpdSession -> MpdHandler/Backend: setvol 50
+Core -> NadTalker: volume = 50
-MpdHandler/Backend -> NadMixer: volume = 50
+Client -> Server: status
-Client -> MpdServer/MpdSession: status
+Server -> Core: status
-MpdServer/MpdSession -> MpdHandler/Backend: status
+Core -> NadTalker: volume?
-MpdHandler/Backend -> NadMixer: volume?
+NadTalker -> Core: volume = 50
-NadMixer -> MpdHandler/Backend: volume = 50
+Core -> Server: status response
-MpdHandler/Backend -> MpdServer/MpdSession: status response
+Server -> Client: status response
-MpdServer/MpdSession -> Client: status response
+despotify -> Core: end of track callback
-despotify -> MpdHandler/Backend: end of track callback
+Core -> despotify: play second track
-MpdHandler/Backend -> despotify: play second track
+Client -> Server: stop
-Client -> MpdServer/MpdSession: stop
+Server -> Core: stop
-MpdServer/MpdSession -> MpdHandler/Backend: stop
+Core -> despotify: stop
-MpdHandler/Backend -> despotify: stop
+Client -> Server: disconnect
-Client -> MpdServer/MpdSession: disconnect
+note over Server: close session
-note over MpdServer/MpdSession: close session

docs/development/internals.rst

@@ -43,11 +43,17 @@ not Mopidy. The red nodes lives in the ``main`` process (running an
     "AlsaMixer" -> "alsaaudio" [ label="use Python library" ]
 
 
-Thread communication
+Thread/process communication
-====================
+============================
 
-.. warning::
+- Everything starts with ``Main``.
-
+- ``Main`` creates a ``Core`` process which runs the frontend, backend, and
-    This is a plan, and does not necessarily reflect what has been implemented.
+  mixer.
+- Mixers *may* create an additional process for communication with external
+  devices, like ``NadTalker`` in this example.
+- Backend libraries *may* have threads of their own, like ``despotify`` here
+  which has additional threads in the ``Core`` process.
+- ``Server`` part currently runs in the same process and thread as ``Main``.
+- ``Client`` is some external client talking to ``Server`` over a socket.
 
 .. image:: /_static/thread_communication.png