feat(schedule): add straw2 algo

Signed-off-by: NaturalSelect <[email protected]>

Cargo.toml

@@ -39,6 +39,8 @@ wasmedge-sdk = { version = "0.10.1" }
 async-channel = "2.1.0"
 sysinfo = "0.29.10"
 ssh2 = "0.9.4"
+rand = "0.8.5"
+numeric = "0.1.4"
 
 # slog-envlogger = { version = "2.1.0", optional = true }
 

src/schedule/master.rs

@@ -1,11 +1,14 @@
 use std::{collections::hash_map::DefaultHasher, hash::Hasher};
 
+use async_raft::NodeId;
 use async_trait::async_trait;
 use axum::{
     http::StatusCode,
     response::{IntoResponse, Redirect, Response},
 };
+use bincode::Options;
 use ws_derive::LogicalModule;
+// use
 
 use super::{executor::Executor, http_handler::RequestHandler};
 use crate::{
@@ -24,6 +27,41 @@ pub struct ScheMaster {
     // view: ScheMasterView,
 }
 
+trait NodeWeighteFetcher {
+    // NOTE: get weight return node weight
+    // larger is better
+    fn get_node_weight(id:NodeId) -> f64;
+}
+
+struct StrawNodeSelector {
+    weight_fetcher:NodeWeighteFetcher,
+    rng:rand::Rng
+}
+
+impl StrawNodeSelector {
+    fn new(weight_fetcher: NodeWeighteFetcher) -> Self { Self { weight_fetcher,rng:rand::thread_rng() } }
+}
+
+// NOTE: Straw2 algorithm
+impl NodeSelector for StrawNodeSelector {
+    fn select_node(&self, all_node_cnt: usize, fn_name: &str) -> NodeID {
+        // NOTE: node id is [1,all_node_cnt]
+        let mut maxStraw:f64 = -1;
+        let mut nodeId:NodeID = 1;
+        let range = Uniform::new(0, 65536);
+        for i in 1..all_node_cnt+1 {
+            let weight = self.weight_fetcher.get_node_weight(i);
+            let mut straw:f64 = range.sample(&mut self.rng);
+            straw = (straw / 65536).ln() / weight;
+            if maxStraw == -1 || maxStraw < straw {
+                maxStraw = straw;
+                nodeId = i;
+            }
+        }
+        return  nodeId;
+    }
+}
+
 trait NodeSelector: Send + Sync + 'static {
     fn select_node(&self, all_node_cnt: usize, fn_name: &str) -> NodeID;
 }