reload the configuration when receiving the SIGHUP signal

NEXT_CHANGELOG.md

@@ -54,6 +54,13 @@ Example of logs in JSON:
 
 By [@bnjjj](https://github.com/bnjjj) in https://github.com/apollographql/router/pull/1982
 
+### Reload the configuration when receiving the SIGHUP signal [Issue #35](https://github.com/apollographql/router/issues/35))
+
+This adds support for reloading configuration when receiving the SIGHUP signal. This only works on unix-like platforms,
+and only with the configuration file.
+
+By [@Geal](https://github.com/Geal) in https://github.com/apollographql/router/pull/2015
+
 ## 🐛 Fixes
 
 ### Fix the deduplication logic in deduplication caching [Issue #1984](https://github.com/apollographql/router/issues/1984))

apollo-router/src/router.rs

@@ -318,10 +318,49 @@ impl ConfigurationSource {
                         .boxed()
                 } else {
                     match ConfigurationSource::read_config(&path) {
-                        Ok(configuration) => stream::once(future::ready(UpdateConfiguration(
-                            Box::new(configuration),
-                        )))
-                        .boxed(),
+                        Ok(configuration) => {
+                            #[cfg(any(test, not(unix)))]
+                            {
+                                stream::once(future::ready(UpdateConfiguration(Box::new(
+                                    configuration,
+                                ))))
+                                .boxed()
+                            }
+
+                            #[cfg(all(not(test), unix))]
+                            {
+                                let mut sighup_stream = tokio::signal::unix::signal(
+                                    tokio::signal::unix::SignalKind::hangup(),
+                                )
+                                .expect("Failed to install SIGHUP signal handler");
+
+                                let (mut tx, rx) = futures::channel::mpsc::channel(1);
+                                tokio::task::spawn(async move {
+                                    while let Some(()) = sighup_stream.recv().await {
+                                        tx.send(()).await.unwrap();
+                                    }
+                                });
+                                futures::stream::select(
+                                    stream::once(future::ready(UpdateConfiguration(Box::new(
+                                        configuration,
+                                    ))))
+                                    .boxed(),
+                                    rx.filter_map(
+                                        move |()| match ConfigurationSource::read_config(&path) {
+                                            Ok(configuration) => future::ready(Some(
+                                                UpdateConfiguration(Box::new(configuration)),
+                                            )),
+                                            Err(err) => {
+                                                tracing::error!("{}", err);
+                                                future::ready(None)
+                                            }
+                                        },
+                                    )
+                                    .boxed(),
+                                )
+                                .boxed()
+                            }
+                        }
                         Err(err) => {
                             tracing::error!("{}", err);
                             stream::empty().boxed()