Auto merge of #3417 - jtgeibel:downloads-counter, r=pietroalbini

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

In production we aren't gracefully shutting down as expected. nginx
does a quick shutdown when receiving a `SIGTERM` and once it exits, it
appears that our process is aborted.

Instead of spawning the backend from the shell script, the backend
process is now responsible for spawning the shell script. This allows
the backend to finish its shutdown work even if the script has already
exited.

`cat` is passed to the nginx buildpack script as our "server", which
will block on `STDIN` so that `nginx` will run until receiving
`SIGTERM`.

r? `@pietroalbini`

Author: bors

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,