From 23b95677bfaf9ac314444d94f418ac8e3f118887 Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Tue, 4 Jun 2024 14:30:28 -0700
Subject: [PATCH] don't use internal state in the node

---
 gg-g_counter/src/main.rs | 47 ++++++++++++++--------------------------
 1 file changed, 16 insertions(+), 31 deletions(-)

diff --git a/gg-g_counter/src/main.rs b/gg-g_counter/src/main.rs
index edc3498..6ee5d04 100644
--- a/gg-g_counter/src/main.rs
+++ b/gg-g_counter/src/main.rs
@@ -1,12 +1,13 @@
 use nebkor_maelstrom::{kv::Kv, mk_payload, Body, Message, Node, Runner};
+use serde_json::Value;
 
 const KEY: &str = "COUNTER";
 
 #[derive(Clone, Default)]
-struct Counter(i64);
+struct Counter;
 
 fn main() {
-    let node = Counter(0);
+    let node = Counter;
 
     let runner = Runner::new(node);
 
@@ -20,14 +21,6 @@ fn main() {
     runner.run(Some(on_init));
 }
 
-fn gossip(neighbors: &[&String], runner: &Runner, val: i64) {
-    let payload = mk_payload(&[("goss", val.into())]);
-    let body = Body::from_type("gossip").with_payload(payload);
-    for node in neighbors {
-        runner.send(node, body.clone());
-    }
-}
-
 impl Node for Counter {
     fn handle(&mut self, runner: &Runner, req: Message) {
         let typ = req.body.typ.as_str();
@@ -37,34 +30,26 @@ impl Node for Counter {
                 let delta = req.body.payload.get("delta").unwrap().as_i64().unwrap();
                 loop {
                     let cur = kv.read(runner, KEY).unwrap().unwrap().as_i64().unwrap();
-                    let cur = cur.max(self.0);
                     let new = cur + delta;
-                    match kv.cas(runner, KEY, cur.into(), new.into(), false) {
-                        Err(_e) => {}
-                        Ok(_) => {
-                            let nodes = runner
-                                .nodes()
-                                .iter()
-                                .filter(|e| e != &&runner.node_id())
-                                .collect::<Vec<_>>();
-                            self.0 = new;
-                            gossip(&nodes, runner, new);
-                            break;
-                        }
+                    if kv.cas(runner, KEY, cur.into(), new.into(), false).is_ok() {
+                        break;
                     }
                 }
                 runner.reply(&req, Body::from_type("add_ok"));
             }
             "read" => {
-                let val = self.0;
-                let body =
-                    Body::from_type("read_ok").with_payload(mk_payload(&[("value", val.into())]));
-                runner.reply(&req, body);
-            }
+                let mut rounds = 0;
+                let mut val = Value::Null;
+                while rounds < 2 {
+                    let v = kv.read(runner, KEY).unwrap().unwrap();
+                    if kv.cas(runner, KEY, v.clone(), v.clone(), false).is_ok() {
+                        rounds += 1;
+                    }
+                    val = v;
+                }
 
-            "gossip" => {
-                let val = req.body.payload.get("goss").unwrap().as_i64().unwrap();
-                self.0 = val.max(self.0);
+                let body = Body::from_type("read_ok").with_payload(mk_payload(&[("value", val)]));
+                runner.reply(&req, body);
             }
             _ => {
                 eprintln!("unknown type: {req:?}");