Boot nginx from the backend app to fix graceful shutdown in production

Procfile

@@ -1,3 +1,3 @@
 release: bin/diesel migration run
-web: ./script/start-web.sh
+web: ./target/release/server
 background_worker: ./target/release/background-worker

script/start-web.sh

@@ -1,12 +1,15 @@
 #! /bin/bash
 set -ue
 
+# Since this script is launched from our app, we tell the nginx
+# buildpack (`bin/start-nginx`) that `cat` is our server.
+
 if [[ -z "${USE_FASTBOOT-}" ]]; then
     unset USE_FASTBOOT
-    bin/start-nginx ./target/release/server
+    bin/start-nginx cat
 else
     export USE_FASTBOOT
     node --optimize_for_size --max_old_space_size=200 fastboot.js &
-    bin/start-nginx ./target/release/server &
+    bin/start-nginx cat &
     wait -n
 fi

src/bin/server.rs

@@ -5,8 +5,8 @@ use cargo_registry::{boot, App, Env};
 use std::{
     borrow::Cow,
     fs::File,
+    process::Command,
     sync::{mpsc::channel, Arc, Mutex},
-    thread,
     time::Duration,
 };
 
@@ -139,9 +139,6 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     println!("listening on port {}", port);
 
-    // Give tokio a chance to spawn the first worker thread
-    thread::sleep(Duration::from_millis(10));
-
     // Creating this file tells heroku to tell nginx that the application is ready
     // to receive traffic.
     if heroku {
@@ -152,6 +149,13 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         };
         println!("Writing to {}", path);
         File::create(path).unwrap();
+
+        // Launch nginx via the Heroku nginx buildpack
+        // `wait()` is never called on the child process, but it should be okay to leave a zombie
+        // process around on shutdown when Heroku is tearing down the entire container anyway.
+        Command::new("./script/start-web.sh")
+            .spawn()
+            .expect("Couldn't spawn nginx");
     }
 
     // Block the main thread until the server has shutdown

src/downloads_counter.rs

@@ -80,7 +80,7 @@ impl DownloadsCounter {
         }
 
         println!(
-            "download_counter all_shards counted_versions={} counted_downloads={} pending_downloads={}",
+            "downloads_counter all_shards counted_versions={} counted_downloads={} pending_downloads={}",
             counted_versions,
             counted_downloads,
             pending_downloads,
@@ -101,7 +101,7 @@ impl DownloadsCounter {
 
         let stats = self.persist_shard(&conn, shard)?;
         println!(
-            "download_counter shard={} counted_versions={} counted_downloads={} pending_downloads={}",
+            "downloads_counter shard={} counted_versions={} counted_downloads={} pending_downloads={}",
             idx,
             stats.counted_versions,
             stats.counted_downloads,