Implement graceful shutdown.

The crux of the implementation is as follows:

  * Configurable ctrl-c, signals that trigger a graceful shutdown.
  * Configurable grace period before forced I/O termination.
  * Programatic triggering via an application-wide method.
  * A future (`Shutdown`) that resolves only when shutdown is requested.

Resolves #180.

core/http/src/listener.rs

@@ -24,7 +24,10 @@ pub trait Listener {
     fn local_addr(&self) -> Option<SocketAddr>;
 
     /// Try to accept an incoming Connection if ready
-    fn poll_accept(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<Self::Connection>>;
+    fn poll_accept(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>
+    ) -> Poll<io::Result<Self::Connection>>;
 }
 
 /// A 'Connection' represents an open connection to a client
@@ -40,16 +43,17 @@ pin_project_lite::pin_project! {
     /// Accept). This type is internal to Rocket.
     #[must_use = "streams do nothing unless polled"]
     pub struct Incoming<L> {
-        listener: L,
         sleep_on_errors: Option<Duration>,
         #[pin]
         pending_error_delay: Option<Sleep>,
+        #[pin]
+        listener: L,
     }
 }
 
 impl<L: Listener> Incoming<L> {
     /// Construct an `Incoming` from an existing `Listener`.
-    pub fn from_listener(listener: L) -> Self {
+    pub fn new(listener: L) -> Self {
         Self {
             listener,
             sleep_on_errors: Some(Duration::from_millis(250)),
@@ -96,7 +100,7 @@ impl<L: Listener> Incoming<L> {
 
             me.pending_error_delay.set(None);
 
-            match me.listener.poll_accept(cx) {
+            match me.listener.as_mut().poll_accept(cx) {
                 Poll::Ready(Ok(stream)) => {
                     return Poll::Ready(Ok(stream));
                 },
@@ -123,7 +127,7 @@ impl<L: Listener> Incoming<L> {
     }
 }
 
-impl<L: Listener + Unpin> Accept for Incoming<L> {
+impl<L: Listener> Accept for Incoming<L> {
     type Conn = L::Connection;
     type Error = io::Error;
 
@@ -171,7 +175,10 @@ impl Listener for TcpListener {
         self.local_addr().ok()
     }
 
-    fn poll_accept(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<Self::Connection>> {
+    fn poll_accept(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>
+    ) -> Poll<io::Result<Self::Connection>> {
         (*self).poll_accept(cx).map_ok(|(stream, _addr)| stream)
     }
 }

core/http/src/tls.rs

@@ -64,7 +64,10 @@ impl Listener for TlsListener {
         self.listener.local_addr().ok()
     }
 
-    fn poll_accept(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<Self::Connection>> {
+    fn poll_accept(
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>
+    ) -> Poll<io::Result<Self::Connection>> {
         loop {
             match self.state {
                 TlsListenerState::Listening => {

core/lib/src/config/config.rs

@@ -7,7 +7,7 @@ use figment::value::{Map, Dict};
 use serde::{Deserialize, Serialize};
 use yansi::Paint;
 
-use crate::config::{TlsConfig, LogLevel};
+use crate::config::{TlsConfig, LogLevel, Shutdown};
 use crate::request::{self, Request, FromRequest};
 use crate::data::Limits;
 
@@ -82,17 +82,16 @@ pub struct Config {
     #[cfg_attr(nightly, doc(cfg(feature = "secrets")))]
     #[serde(serialize_with = "SecretKey::serialize_zero")]
     pub secret_key: SecretKey,
-    /// The directory to store temporary files in. **(default:
-    /// [`std::env::temp_dir`]).
+    /// Directory to store temporary files in. **(default:
+    /// [`std::env::temp_dir()`])**
     pub temp_dir: PathBuf,
     /// Max level to log. **(default: _debug_ `normal` / _release_ `critical`)**
     pub log_level: LogLevel,
+    /// Graceful shutdown configuration. **(default: [`Shutdown::default()`])**
+    pub shutdown: Shutdown,
     /// Whether to use colors and emoji when logging. **(default: `true`)**
     #[serde(deserialize_with = "figment::util::bool_from_str_or_int")]
     pub cli_colors: bool,
-    /// Whether `ctrl-c` initiates a server shutdown. **(default: `true`)**
-    #[serde(deserialize_with = "figment::util::bool_from_str_or_int")]
-    pub ctrlc: bool,
 }
 
 impl Default for Config {
@@ -152,7 +151,7 @@ impl Config {
             temp_dir: std::env::temp_dir(),
             log_level: LogLevel::Normal,
             cli_colors: true,
-            ctrlc: true,
+            shutdown: Shutdown::default(),
         }
     }
 
@@ -318,6 +317,7 @@ impl Config {
         launch_info_!("temp dir: {}", Paint::default(&self.temp_dir.display()).bold());
         launch_info_!("log level: {}", Paint::default(self.log_level).bold());
         launch_info_!("cli colors: {}", Paint::default(&self.cli_colors).bold());
+        launch_info_!("shutdown: {}", Paint::default(&self.shutdown).bold());
 
         // Check for now depreacted config values.
         for (key, replacement) in Self::DEPRECATED_KEYS {
@@ -398,8 +398,8 @@ impl Config {
     /// The stringy parameter name for setting/extracting [`Config::log_level`].
     pub const LOG_LEVEL: &'static str = "log_level";
 
-    /// The stringy parameter name for setting/extracting [`Config::ctrlc`].
-    pub const CTRLC: &'static str = "ctrlc";
+    /// The stringy parameter name for setting/extracting [`Config::shutdown`].
+    pub const SHUTDOWN: &'static str = "shutdown";
 }
 
 impl Provider for Config {

core/lib/src/config/mod.rs

@@ -113,6 +113,7 @@
 
 mod config;
 mod tls;
+mod shutdown;
 
 #[cfg(feature = "secrets")]
 mod secret_key;
@@ -121,19 +122,24 @@ mod secret_key;
 
 pub use config::Config;
 pub use crate::log::LogLevel;
+pub use shutdown::Shutdown;
 pub use tls::TlsConfig;
 
 #[cfg(feature = "secrets")]
 #[cfg_attr(nightly, doc(cfg(feature = "secrets")))]
 pub use secret_key::SecretKey;
 
+#[cfg(unix)]
+#[cfg_attr(nightly, doc(cfg(unix)))]
+pub use shutdown::Sig;
+
 #[cfg(test)]
 mod tests {
     use std::net::Ipv4Addr;
     use figment::{Figment, Profile};
     use pretty_assertions::assert_eq;
 
-    use crate::config::{Config, TlsConfig};
+    use crate::config::{Config, TlsConfig, Shutdown};
     use crate::log::LogLevel;
     use crate::data::{Limits, ToByteUnit};
 
@@ -217,7 +223,7 @@ mod tests {
 
             jail.create_file("Rocket.toml", r#"
                 [global]
-                ctrlc = 0
+                shutdown.ctrlc = 0
 
                 [global.tls]
                 certs = "/ssl/cert.pem"
@@ -231,7 +237,7 @@ mod tests {
 
             let config = Config::from(Config::figment());
             assert_eq!(config, Config {
-                ctrlc: false,
+                shutdown: Shutdown { ctrlc: false, ..Default::default() },
                 tls: Some(TlsConfig::from_paths("/ssl/cert.pem", "/ssl/key.pem")),
                 limits: Limits::default()
                     .limit("forms", 1.mebibytes())