1 files changed, 56 insertions, 0 deletions
diff --git a/notes/architecture.md b/notes/architecture.md
new file mode 100644
index 0000000..c9268c9
--- /dev/null
+++ b/notes/architecture.md
@@ -0,0 +1,56 @@
+
+peers wrap connections with given clients (any transport type). each peer can
+be talking about multiple feeds. state consists of which feeds, what the remote
+has (feed, bitmap), and what chunks (feed, index) have been requested
+("in-flight"). connection logic runs in threads, passes back and forth entire
+messages in channels.
+
+    ConnCommand
+        Send(DatNetMessage)
+        Terminate()
+
+    ConnReply
+        Received(DatNetMessage)
+        Disconnected()
+
+A synchronizer event loop has local feeds (storage) and a bunch of peers. Extra
+state includes mode configuration, feeds, "wanted" bitmap for each feed.
+Callbacks for certain feed events allow for extension (eg, hyperdrive stuff).
+Needs a timer event. 
+
+Use chan and chan-signal for now (MPSC style)... tokio will be the future but
+seems too unstable for now. mio is too low-level to use on it's own (eg, no
+timers, no threads). Use two threads per peer: a "main" thread that does
+connection setup, `chan_select`, and blocking writes, and a "reader" thread
+that does blocking reads of entire messages (writing either into the main
+thread or skipping straight to the output channel). Got this pattern from the
+`rusty_torrent` package. Need to set some write timeout. Synchronizer handles
+cleanup if peer isn't replying/heartbeating.
+
+Probably want a dedicated discovery thread/worker in the future, but for now
+just do it synchronously and connect to up to N peers to start.
+
+Synchronize will select on:
+
+    signal
+        graceful shutdown
+    unified_inbound
+        feed: depends on state; ignore for now
+        handshake: error, close connection?
+        have, info: update PeerState bitmap
+        unhave, info, want, unwant: ignore for now
+        request: depends on state; read from storage
+        cancel: ignore for now
+        data: write to storage, clear pending; send new request
+    tick
+        check peer states, kill if too slow
+        dump status to command line
+
+Synchronize needs state:
+- "tried" peers, so we don't retry in a loop if they fail
+
+Synchronize options:
+- whether or not to hook signals
+
+Where does drive logic live? Plugin, via callback, to Synchronize? Let's just
+fold it in to synchronizer for now, as a mode flag.