From ebf76784e7fe229fe6628b13e933a1ed6d6e6b97 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Sat, 28 Aug 2021 19:21:22 +0200
Subject: [PATCH] server main: replace db_pool_index Mutex with AtomicUsize

---
 server/src/main.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/server/src/main.rs b/server/src/main.rs
index 52fa9f1..1a95c6a 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -4,7 +4,7 @@
 extern crate gotham_derive;
 
 use core::f64::consts::PI;
-use std::sync::{Arc, Mutex};
+use std::sync::{Arc, atomic::{AtomicUsize, Ordering}, Mutex};
 use gotham::{
     handler::assets::FileOptions,
     router::builder::{DefineSingleRoute, DrawRoutes},
@@ -24,18 +24,21 @@ mod tiles;
 #[derive(Clone, StateData)]
 pub struct AppState {
     pub db_pool: Vec<Arc<Mutex<postgres::Client>>>,
-    pub db_pool_index: Arc<Mutex<usize>>,
+    pub db_pool_index: Arc<AtomicUsize>,
 }
 
 impl AppState {
     pub fn with_db<F: Fn(&mut postgres::Client) -> R, R>(&self, f: F) -> R {
-        let mut db_pool_index = self.db_pool_index.lock().unwrap();
-        let mut db = self.db_pool[*db_pool_index].lock().unwrap();
-
-        *db_pool_index += 1;
-        if *db_pool_index >= self.db_pool.len() {
-            *db_pool_index = 0;
-        }
+        let db_pool_len = self.db_pool.len();
+        let db_pool_index = self.db_pool_index.fetch_update(
+            Ordering::SeqCst, Ordering::SeqCst, |mut db_pool_index| {
+                db_pool_index += 1;
+                if db_pool_index >= db_pool_len {
+                    db_pool_index = 0;
+                }
+                Some(db_pool_index)
+            }).unwrap();
+        let mut db = self.db_pool[db_pool_index].lock().unwrap();
 
         f(&mut db)
     }
@@ -136,7 +139,7 @@ fn main() {
 
     let state = AppState {
         db_pool,
-        db_pool_index: Arc::new(Mutex::new(0)),
+        db_pool_index: Arc::new(AtomicUsize::new(0)),
     };
     let (chain, pipelines) = single_pipeline(
         single_middleware(