From 8f5799211ca1aa2f6b79dfac7fb4cf7acb9fe9e9 Mon Sep 17 00:00:00 2001
From: Edward Shen <code@eddie.sh>
Date: Thu, 22 Jul 2021 13:37:32 -0400
Subject: [PATCH] Try reserve port during startup

---
 src/main.rs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index 0e00bdd..40a66fe 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -87,7 +87,6 @@ async fn main() -> Result<(), Box<dyn Error>> {
     // Logging and warnings
     //
 
-    // SimpleLogger::new().with_level(config.log_level).init()?;
     tracing_subscriber::fmt()
         .with_max_level(config.log_level)
         .init();
@@ -121,6 +120,13 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // HTTP Server init
 
+    // Try bind to provided port first
+    let port_reservation = std::net::TcpListener::bind(bind_address);
+    if let Err(e) = port_reservation {
+        error!("Failed to bind to port!");
+        return Err(e.into());
+    };
+
     let server = if OFFLINE_MODE.load(Ordering::Acquire) {
         ServerState::init_offline()
     } else {
@@ -225,6 +231,10 @@ async fn main() -> Result<(), Box<dyn Error>> {
     })
     .shutdown_timeout(60);
 
+    // drop port reservation, might have a TOCTOU but it's not a big deal; this
+    // is just a best effort.
+    std::mem::drop(port_reservation);
+
     if disable_tls {
         server.bind(bind_address)?.run().await?;
     } else {