graph, node: Add descriptive comments, restructure shutdown sending

graph/src/util/log.rs

@@ -5,7 +5,8 @@ use slog_async;
 use slog_envlogger;
 use slog_term;
 use std::sync::Mutex;
-use std::{env, panic};
+use std::time::{Duration, Instant};
+use std::{env, panic, process, thread};
 
 pub fn logger(show_debug: bool) -> Logger {
     let decorator = slog_term::TermDecorator::new().build();
@@ -73,14 +74,19 @@ pub fn register_panic_hook(
             }
         };
 
-        if let Ok(ref mut mutex) = shutdown_sender.lock() {
-            if let Some(sender) = mutex.take() {
-                sender
-                    .send(())
-                    .map(|_| ())
-                    .map_err(|_| ())
-                    .expect("Failed to signal shutdown")
-            }
-        };
+        // Send a shutdown signal to main which will attempt to cleanly shutdown the runtime
+        // After sending shutdown, the thread sleeps for 3 seconds then forces the process to
+        // exit because the shutdown is not always able to cleanly exit all workers
+        shutdown_sender
+            .lock()
+            .unwrap()
+            .take()
+            .expect("Shutdown signal already sent")
+            .send(())
+            .map(|_| ())
+            .map_err(|_| ())
+            .expect("Failed to signal shutdown");
+        thread::sleep(Duration::from_millis(3000));
+        process::exit(1);
     }));
 }

node/src/main.rs

@@ -25,8 +25,6 @@ use std::env;
 use std::net::ToSocketAddrs;
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
-use std::{env, process, thread};
-use url::Url;
 
 use graph::components::{forward, forward2};
 use graph::prelude::{JsonRpcServer as JsonRpcServerTrait, *};
@@ -62,6 +60,7 @@ fn main() {
     let timer = Timer::default();
     let timer_handle = timer.handle();
 
+    // Shutdown the runtime after a panic
     std::thread::spawn(|| {
         shutdown_receiver
             .wait()
@@ -70,8 +69,6 @@ fn main() {
                     .shutdown_now()
                     .wait()
                     .expect("Failed to shutdown Tokio Runtime");
-                thread::sleep(Duration::from_millis(3000));
-                process::exit(1)
             }).expect("Runtime shutdown process did not finish");
     });
 
@@ -497,7 +494,7 @@ fn async_main() -> impl Future<Item = (), Error = ()> + Send + 'static {
             .expect("Failed to start GraphQL subscription server"),
     );
 
-    future::ok(())
+    future::empty()
 }
 
 /// Parses an Ethereum connection string and returns the network name and Ethereum node.