total-order multicast pseudocode

2 files changed, 35 insertions, 47 deletions

diff --git a/doc/sequencer.pseudo b/doc/sequencer.pseudo
deleted file mode 100644
index f511eee..0000000
--- a/doc/sequencer.pseudo
+++ /dev/null
@@ -1,47 +0,0 @@
-// Sequencer based on "Distributed Systems: Concepts and Design" 5e, Coulouris et
-// al. (2012) pp. 654-655. Depends on reliable multicast, implemented here as the
-// Trans protocol.
-
-type dataMsg struct {
-	id int
-	data
-}
-
-type orderMsg struct {
-	id int
-	seq int
-}
-
-class groupMember {
-	seq := 0
-	holdback := new Queue[dataMsg]
-	deliver := new Queue[dataMsg]
-	rMulticast := new Trans
-
-	multicast(m dataMsg) {
-		rMulticast.send(m)
-	}
-
-	on rMulticast.recv(m dataMsg) {
-		holdback.enqueue(m)
-	}
-
-	on rMulticast.recv(m orderMsg) {
-		wait until m.id in holdback && seq == m.seq
-		data := delete(m.id, holdback)
-		deliver.enqueue(data)
-		seq++
-	}
-}
-
-// Sequencer is also a member of the multicast group.
-class sequencer {
-	seq := 0
-	rMulticast := new  Trans
-
-	on rMulticast.recv(m dataMsg) {
-		order := orderMsg{m.id, seq}
-		rMulticast.send(order)
-		seq++
-	}
-}
diff --git a/doc/tomulticast.pseudo b/doc/tomulticast.pseudo
new file mode 100644
index 0000000..332ba32
--- /dev/null
+++ b/doc/tomulticast.pseudo
@@ -0,0 +1,35 @@
+type message struct {
+	seq int
+	payload
+}
+
+class sequencer {
+	var seq = 0
+
+	// Receive a request from the FE.
+	// Attach sequence number and multicast to RMs.
+	on rUnicastReceive(payload) {
+		rMulticastSend(message{seq, payload})
+		seq++
+	}
+}
+
+class receiver {
+	var seq = 0
+	var holdback Queue[message]
+
+	// Receive from sequencer.
+	on rMulticastReceive(m message) {
+		append(holdback, m)
+		trydeliver()
+	}
+
+	trydeliver() {
+		if t.e. m in holdback s.t. m.seq == seq+1 {
+			remove(m, holdback)
+			deliver(m)
+			seq++
+			trydeliver()
+		}
+	}
+}