feat(core): Log runtime names during Server shutdown

Log the names of runtimes during Server shutdown.

Motivation: server shutdown can take quite a long time if the runtimes
don't exit.
It's hard to debug why this is the case, because there is no indiciation
in the logs which service is pending.

This small change modifies the server to log the name of the service
whose runtime is being waited for.

Author: theduke

pingora-core/src/server/mod.rs

@@ -335,10 +335,12 @@ impl Server {
         #[cfg(all(not(debug_assertions), feature = "sentry"))]
         let _guard = self.sentry.as_ref().map(|opts| sentry::init(opts.clone()));
 
-        let mut runtimes: Vec<Runtime> = Vec::new();
+        // Holds a tuple of runtimes and the service name.
+        let mut runtimes: Vec<(Runtime, String)> = Vec::new();
 
         while let Some(service) = self.services.pop() {
             let threads = service.threads().unwrap_or(conf.threads);
+            let name = service.name().to_string();
             let runtime = Server::run_service(
                 service,
                 #[cfg(unix)]
@@ -347,7 +349,7 @@ impl Server {
                 threads,
                 conf.work_stealing,
             );
-            runtimes.push(runtime);
+            runtimes.push((runtime, name));
         }
 
         // blocked on main loop so that it runs forever
@@ -379,20 +381,23 @@ impl Server {
                     .unwrap_or(5),
             ),
         };
-        let shutdowns: Vec<_> = runtimes
+        let shutdowns: Vec<(_, String)> = runtimes
             .into_iter()
-            .map(|rt| {
+            .map(|(rt, name)| {
                 info!("Waiting for runtimes to exit!");
-                thread::spawn(move || {
+                let join = thread::spawn(move || {
                     rt.shutdown_timeout(shutdown_timeout);
                     thread::sleep(shutdown_timeout)
-                })
+                });
+                (join, name)
             })
             .collect();
-        for shutdown in shutdowns {
+        for (shutdown, name) in shutdowns {
+            info!("Waiting for service runtime {} to exit", name);
             if let Err(e) = shutdown.join() {
-                error!("Failed to shutdown runtime: {:?}", e);
+                error!("Failed to shutdown service runtime {}: {:?}", name, e);
             }
+            debug!("Service runtime {} has exited", name);
         }
         info!("All runtimes exited, exiting now");
         std::process::exit(0)