add actix single threaded runtime

Cargo.toml

@@ -18,6 +18,7 @@ members = [
   "./",
   "actix-codec",
   "actix-service",
+  "actix-rt",
 ]
 
 [package.metadata.docs.rs]

actix-rt/CHANGES.md

@@ -0,0 +1,5 @@
+# Changes
+
+## [0.1.0] - 2018-12-09
+
+* Move codec to separate crate

actix-rt/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "actix-rt"
+version = "0.1.0"
+authors = ["Nikolay Kim <fafhrd91@gmail.com>"]
+description = "Actix runtime"
+keywords = ["network", "framework", "async", "futures"]
+homepage = "https://actix.rs"
+repository = "https://github.com/actix/actix-net.git"
+documentation = "https://docs.rs/actix-rt/"
+categories = ["network-programming", "asynchronous"]
+license = "MIT/Apache-2.0"
+exclude = [".gitignore", ".travis.yml", ".cargo/config", "appveyor.yml"]
+edition = "2018"
+workspace = "../"
+
+[lib]
+name = "actix_rt"
+path = "src/lib.rs"
+
+[dependencies]
+log = "0.4"
+bytes = "0.4"
+futures = "0.1.24"
+tokio-current-thread = "0.1"
+tokio-executor = "0.1.5"
+tokio-reactor = "0.1.7"
+tokio-timer = "0.2.8"

actix-rt/src/arbiter.rs

@@ -0,0 +1,238 @@
+#![allow(
+    clippy::borrow_interior_mutable_const,
+    clippy::declare_interior_mutable_const
+)]
+use std::cell::{Cell, RefCell};
+use std::collections::HashMap;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::thread;
+
+use futures::sync::mpsc::{unbounded, UnboundedReceiver, UnboundedSender};
+use futures::sync::oneshot::{channel, Sender};
+use futures::{future, Async, Future, IntoFuture, Poll, Stream};
+use tokio_current_thread::spawn;
+
+use crate::builder::Builder;
+use crate::system::System;
+
+thread_local!(
+    static ADDR: RefCell<Option<Arbiter>> = RefCell::new(None);
+    static RUNNING: Cell<bool> = Cell::new(false);
+    static Q: RefCell<Vec<Box<Future<Item = (), Error = ()>>>> = RefCell::new(Vec::new());
+);
+
+pub(crate) const COUNT: AtomicUsize = AtomicUsize::new(0);
+
+#[derive(Debug)]
+pub(crate) enum ArbiterCommand {
+    Stop,
+}
+
+#[derive(Debug, Clone)]
+pub struct Arbiter(UnboundedSender<ArbiterCommand>);
+
+impl Default for Arbiter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Arbiter {
+    pub(crate) fn new_system() -> Self {
+        let (tx, rx) = unbounded();
+
+        let arb = Arbiter(tx);
+        ADDR.with(|cell| *cell.borrow_mut() = Some(arb.clone()));
+        RUNNING.with(|cell| cell.set(false));
+        Arbiter::spawn(ArbiterController { stop: None, rx });
+
+        arb
+    }
+
+    /// Stop arbiter
+    pub fn stop(&self) {
+        let _ = self.0.unbounded_send(ArbiterCommand::Stop);
+    }
+
+    /// Spawn new thread and run event loop in spawned thread.
+    /// Returns address of newly created arbiter.
+    pub fn new() -> Arbiter {
+        let id = COUNT.fetch_add(1, Ordering::Relaxed);
+        let name = format!("actix-rt:worker:{}", id);
+        let sys = System::current();
+        let (arb_tx, arb_rx) = unbounded();
+        let arb_tx2 = arb_tx.clone();
+
+        let _ = thread::Builder::new().name(name.clone()).spawn(move || {
+            let mut rt = Builder::new().build_rt().expect("Can not create Runtime");
+            let arb = Arbiter(arb_tx);
+
+            let (stop, stop_rx) = channel();
+            RUNNING.with(|cell| cell.set(true));
+
+            System::set_current(sys);
+
+            // start arbiter controller
+            rt.spawn(ArbiterController {
+                stop: Some(stop),
+                rx: arb_rx,
+            });
+            ADDR.with(|cell| *cell.borrow_mut() = Some(arb.clone()));
+
+            // register arbiter
+            let _ = System::current()
+                .sys()
+                .unbounded_send(SystemCommand::RegisterArbiter(id, arb.clone()));
+
+            // run loop
+            let _ = match rt.block_on(stop_rx) {
+                Ok(code) => code,
+                Err(_) => 1,
+            };
+
+            // unregister arbiter
+            let _ = System::current()
+                .sys()
+                .unbounded_send(SystemCommand::UnregisterArbiter(id));
+        });
+
+        Arbiter(arb_tx2)
+    }
+
+    pub(crate) fn run_system() {
+        RUNNING.with(|cell| cell.set(true));
+        Q.with(|cell| {
+            let mut v = cell.borrow_mut();
+            for fut in v.drain(..) {
+                spawn(fut);
+            }
+        });
+    }
+
+    pub(crate) fn stop_system() {
+        RUNNING.with(|cell| cell.set(false));
+    }
+
+    /// Executes a future on the current thread.
+    pub fn spawn<F>(future: F)
+    where
+        F: Future<Item = (), Error = ()> + 'static,
+    {
+        RUNNING.with(move |cell| {
+            if cell.get() {
+                spawn(Box::new(future));
+            } else {
+                Q.with(move |cell| cell.borrow_mut().push(Box::new(future)));
+            }
+        });
+    }
+
+    /// Executes a future on the current thread.
+    pub fn spawn_fn<F, R>(f: F)
+    where
+        F: FnOnce() -> R + 'static,
+        R: IntoFuture<Item = (), Error = ()> + 'static,
+    {
+        Arbiter::spawn(future::lazy(f))
+    }
+}
+
+struct ArbiterController {
+    stop: Option<Sender<i32>>,
+    rx: UnboundedReceiver<ArbiterCommand>,
+}
+
+impl Drop for ArbiterController {
+    fn drop(&mut self) {
+        if thread::panicking() {
+            eprintln!("Panic in Arbiter thread, shutting down system.");
+            if System::current().stop_on_panic() {
+                System::current().stop_with_code(1)
+            }
+        }
+    }
+}
+
+impl Future for ArbiterController {
+    type Item = ();
+    type Error = ();
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        match self.rx.poll() {
+            Ok(Async::Ready(None)) | Err(_) => Ok(Async::Ready(())),
+            Ok(Async::Ready(Some(item))) => match item {
+                ArbiterCommand::Stop => {
+                    if let Some(stop) = self.stop.take() {
+                        let _ = stop.send(0);
+                    };
+                    Ok(Async::Ready(()))
+                }
+            },
+            Ok(Async::NotReady) => Ok(Async::NotReady),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) enum SystemCommand {
+    Exit(i32),
+    RegisterArbiter(usize, Arbiter),
+    UnregisterArbiter(usize),
+}
+
+#[derive(Debug)]
+pub(crate) struct SystemArbiter {
+    stop: Option<Sender<i32>>,
+    commands: UnboundedReceiver<SystemCommand>,
+    arbiters: HashMap<usize, Arbiter>,
+}
+
+impl SystemArbiter {
+    pub(crate) fn new(stop: Sender<i32>, commands: UnboundedReceiver<SystemCommand>) -> Self {
+        SystemArbiter {
+            commands,
+            stop: Some(stop),
+            arbiters: HashMap::new(),
+        }
+    }
+}
+
+impl Future for SystemArbiter {
+    type Item = ();
+    type Error = ();
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        match self.commands.poll() {
+            Ok(Async::Ready(None)) | Err(_) => return Ok(Async::Ready(())),
+            Ok(Async::Ready(Some(cmd))) => match cmd {
+                SystemCommand::Exit(code) => {
+                    // stop arbiters
+                    for arb in self.arbiters.values() {
+                        arb.stop();
+                    }
+                    // stop event loop
+                    if let Some(stop) = self.stop.take() {
+                        let _ = stop.send(code);
+                    }
+                }
+                SystemCommand::RegisterArbiter(name, hnd) => {
+                    self.arbiters.insert(name, hnd);
+                }
+                SystemCommand::UnregisterArbiter(name) => {
+                    self.arbiters.remove(&name);
+                }
+            },
+            Ok(Async::NotReady) => return Ok(Async::NotReady),
+        }
+        Ok(Async::NotReady)
+    }
+}
+
+// /// Execute function in arbiter's thread
+// impl<I: Send, E: Send> Handler<Execute<I, E>> for SystemArbiter {
+//     type Result = Result<I, E>;
+
+//     fn handle(&mut self, msg: Execute<I, E>, _: &mut Context<Self>) -> Result<I, E> {
+//         msg.exec()
+//     }
+// }

actix-rt/src/builder.rs

@@ -0,0 +1,175 @@
+use std::borrow::Cow;
+use std::io;
+
+use futures::future::{lazy, Future};
+use futures::sync::mpsc::unbounded;
+use futures::sync::oneshot::{channel, Receiver};
+
+use tokio_current_thread::CurrentThread;
+use tokio_reactor::Reactor;
+use tokio_timer::clock::Clock;
+use tokio_timer::timer::Timer;
+
+use crate::arbiter::{Arbiter, SystemArbiter};
+use crate::runtime::Runtime;
+use crate::system::System;
+
+/// Builder struct for a actix runtime.
+///
+/// Either use `Builder::build` to create a system and start actors.
+/// Alternatively, use `Builder::run` to start the tokio runtime and
+/// run a function in its context.
+pub struct Builder {
+    /// Name of the System. Defaults to "actix" if unset.
+    name: Cow<'static, str>,
+
+    /// The clock to use
+    clock: Clock,
+
+    /// Whether the Arbiter will stop the whole System on uncaught panic. Defaults to false.
+    stop_on_panic: bool,
+}
+
+impl Builder {
+    pub(crate) fn new() -> Self {
+        Builder {
+            name: Cow::Borrowed("actix"),
+            clock: Clock::new(),
+            stop_on_panic: false,
+        }
+    }
+
+    /// Sets the name of the System.
+    pub fn name<T: Into<String>>(mut self, name: T) -> Self {
+        self.name = Cow::Owned(name.into());
+        self
+    }
+
+    /// Set the Clock instance that will be used by this System.
+    ///
+    /// Defaults to the system clock.
+    pub fn clock(mut self, clock: Clock) -> Self {
+        self.clock = clock;
+        self
+    }
+
+    /// Sets the option 'stop_on_panic' which controls whether the System is stopped when an
+    /// uncaught panic is thrown from a worker thread.
+    ///
+    /// Defaults to false.
+    pub fn stop_on_panic(mut self, stop_on_panic: bool) -> Self {
+        self.stop_on_panic = stop_on_panic;
+        self
+    }
+
+    /// Create new System.
+    ///
+    /// This method panics if it can not create tokio runtime
+    pub fn build(self) -> SystemRunner {
+        self.create_runtime(|| {})
+    }
+
+    /// This function will start tokio runtime and will finish once the
+    /// `System::stop()` message get called.
+    /// Function `f` get called within tokio runtime context.
+    pub fn run<F>(self, f: F) -> i32
+    where
+        F: FnOnce() + 'static,
+    {
+        self.create_runtime(f).run()
+    }
+
+    fn create_runtime<F>(self, f: F) -> SystemRunner
+    where
+        F: FnOnce() + 'static,
+    {
+        let (stop_tx, stop) = channel();
+        let (sys_sender, sys_receiver) = unbounded();
+
+        let arbiter = Arbiter::new_system();
+        let system = System::construct(sys_sender, arbiter.clone(), self.stop_on_panic);
+
+        // system arbiter
+        let arb = SystemArbiter::new(stop_tx, sys_receiver);
+
+        let mut rt = self.build_rt().unwrap();
+        rt.spawn(arb);
+
+        // init system arbiter and run configuration method
+        let _ = rt.block_on(lazy(move || {
+            f();
+            Ok::<_, ()>(())
+        }));
+
+        SystemRunner { rt, stop, system }
+    }
+
+    pub(crate) fn build_rt(&self) -> io::Result<Runtime> {
+        // We need a reactor to receive events about IO objects from kernel
+        let reactor = Reactor::new()?;
+        let reactor_handle = reactor.handle();
+
+        // Place a timer wheel on top of the reactor. If there are no timeouts to fire, it'll let the
+        // reactor pick up some new external events.
+        let timer = Timer::new_with_now(reactor, self.clock.clone());
+        let timer_handle = timer.handle();
+
+        // And now put a single-threaded executor on top of the timer. When there are no futures ready
+        // to do something, it'll let the timer or the reactor to generate some new stimuli for the
+        // futures to continue in their life.
+        let executor = CurrentThread::new_with_park(timer);
+
+        Ok(Runtime::new2(
+            reactor_handle,
+            timer_handle,
+            self.clock.clone(),
+            executor,
+        ))
+    }
+}
+
+/// Helper object that runs System's event loop
+#[must_use = "SystemRunner must be run"]
+#[derive(Debug)]
+pub struct SystemRunner {
+    rt: Runtime,
+    stop: Receiver<i32>,
+    system: System,
+}
+
+impl SystemRunner {
+    /// This function will start event loop and will finish once the
+    /// `System::stop()` function is called.
+    pub fn run(self) -> i32 {
+        let SystemRunner { mut rt, stop, .. } = self;
+
+        // run loop
+        let _ = rt.block_on(lazy(move || {
+            Arbiter::run_system();
+            Ok::<_, ()>(())
+        }));
+        let code = match rt.block_on(stop) {
+            Ok(code) => code,
+            Err(_) => 1,
+        };
+        Arbiter::stop_system();
+        code
+    }
+
+    /// Execute a future and wait for result.
+    pub fn block_on<F, I, E>(&mut self, fut: F) -> Result<I, E>
+    where
+        F: Future<Item = I, Error = E>,
+    {
+        let _ = self.rt.block_on(lazy(move || {
+            Arbiter::run_system();
+            Ok::<_, ()>(())
+        }));
+        let res = self.rt.block_on(fut);
+        let _ = self.rt.block_on(lazy(move || {
+            Arbiter::stop_system();
+            Ok::<_, ()>(())
+        }));
+        res
+    }
+}

actix-rt/src/lib.rs

@@ -0,0 +1,12 @@
+//! A runtime implementation that runs everything on the current thread.
+
+mod arbiter;
+mod builder;
+mod runtime;
+mod system;
+
+pub use self::builder::{Builder, SystemRunner};
+pub use self::runtime::{Handle, Runtime};
+pub use self::system::System;
+// pub use tokio_current_thread::spawn;
+// pub use tokio_current_thread::TaskExecutor;

actix-rt/src/mod.rs

@@ -0,0 +1,92 @@
+//! A runtime implementation that runs everything on the current thread.
+//!
+//! [`current_thread::Runtime`][rt] is similar to the primary
+//! [`Runtime`][concurrent-rt] except that it runs all components on the current
+//! thread instead of using a thread pool. This means that it is able to spawn
+//! futures that do not implement `Send`.
+//!
+//! Same as the default [`Runtime`][concurrent-rt], the
+//! [`current_thread::Runtime`][rt] includes:
+//!
+//! * A [reactor] to drive I/O resources.
+//! * An [executor] to execute tasks that use these I/O resources.
+//! * A [timer] for scheduling work to run after a set period of time.
+//!
+//! Note that [`current_thread::Runtime`][rt] does not implement `Send` itself
+//! and cannot be safely moved to other threads.
+//!
+//! # Spawning from other threads
+//!
+//! While [`current_thread::Runtime`][rt] does not implement `Send` and cannot
+//! safely be moved to other threads, it provides a `Handle` that can be sent
+//! to other threads and allows to spawn new tasks from there.
+//!
+//! For example:
+//!
+//! ```
+//! # extern crate tokio;
+//! # extern crate futures;
+//! use tokio::runtime::current_thread::Runtime;
+//! use tokio::prelude::*;
+//! use std::thread;
+//!
+//! # fn main() {
+//! let mut runtime = Runtime::new().unwrap();
+//! let handle = runtime.handle();
+//!
+//! thread::spawn(move || {
+//!     handle.spawn(future::ok(()));
+//! }).join().unwrap();
+//!
+//! # /*
+//! runtime.run().unwrap();
+//! # */
+//! # }
+//! ```
+//!
+//! # Examples
+//!
+//! Creating a new `Runtime` and running a future `f` until its completion and
+//! returning its result.
+//!
+//! ```
+//! use tokio::runtime::current_thread::Runtime;
+//! use tokio::prelude::*;
+//!
+//! let mut runtime = Runtime::new().unwrap();
+//!
+//! // Use the runtime...
+//! // runtime.block_on(f); // where f is a future
+//! ```
+//!
+//! [rt]: struct.Runtime.html
+//! [concurrent-rt]: ../struct.Runtime.html
+//! [chan]: https://docs.rs/futures/0.1/futures/sync/mpsc/fn.channel.html
+//! [reactor]: ../../reactor/struct.Reactor.html
+//! [executor]: https://tokio.rs/docs/getting-started/runtime-model/#executors
+//! [timer]: ../../timer/index.html
+
+mod builder;
+mod runtime;
+
+pub use self::builder::Builder;
+pub use self::runtime::{Runtime, Handle};
+pub use tokio_current_thread::spawn;
+pub use tokio_current_thread::TaskExecutor;
+
+use futures::Future;
+
+/// Run the provided future to completion using a runtime running on the current thread.
+///
+/// This first creates a new [`Runtime`], and calls [`Runtime::block_on`] with the provided future,
+/// which blocks the current thread until the provided future completes. It then calls
+/// [`Runtime::run`] to wait for any other spawned futures to resolve.
+pub fn block_on_all<F>(future: F) -> Result<F::Item, F::Error>
+where
+    F: Future,
+{
+    let mut r = Runtime::new().expect("failed to start runtime on current thread");
+    let v = r.block_on(future)?;
+    r.run().expect("failed to resolve remaining futures");
+    Ok(v)
+}

actix-rt/src/runtime.rs

@@ -0,0 +1,236 @@
+use std::error::Error;
+use std::fmt;
+use std::io;
+
+use futures::{future, Future};
+use tokio_current_thread::Handle as ExecutorHandle;
+use tokio_current_thread::{self as current_thread, CurrentThread};
+use tokio_executor;
+use tokio_reactor::{self, Reactor};
+use tokio_timer::clock::{self, Clock};
+use tokio_timer::timer::{self, Timer};
+
+use crate::builder::Builder;
+
+/// Single-threaded runtime provides a way to start reactor
+/// and executor on the current thread.
+///
+/// See [module level][mod] documentation for more details.
+///
+/// [mod]: index.html
+#[derive(Debug)]
+pub struct Runtime {
+    reactor_handle: tokio_reactor::Handle,
+    timer_handle: timer::Handle,
+    clock: Clock,
+    executor: CurrentThread<Timer<Reactor>>,
+}
+
+/// Handle to spawn a future on the corresponding `CurrentThread` runtime instance
+#[derive(Debug, Clone)]
+pub struct Handle(ExecutorHandle);
+
+impl Handle {
+    /// Spawn a future onto the `CurrentThread` runtime instance corresponding to this handle
+    ///
+    /// # Panics
+    ///
+    /// This function panics if the spawn fails. Failure occurs if the `CurrentThread`
+    /// instance of the `Handle` does not exist anymore.
+    pub fn spawn<F>(&self, future: F) -> Result<(), tokio_executor::SpawnError>
+    where
+        F: Future<Item = (), Error = ()> + Send + 'static,
+    {
+        self.0.spawn(future)
+    }
+
+    /// Provides a best effort **hint** to whether or not `spawn` will succeed.
+    ///
+    /// This function may return both false positives **and** false negatives.
+    /// If `status` returns `Ok`, then a call to `spawn` will *probably*
+    /// succeed, but may fail. If `status` returns `Err`, a call to `spawn` will
+    /// *probably* fail, but may succeed.
+    ///
+    /// This allows a caller to avoid creating the task if the call to `spawn`
+    /// has a high likelihood of failing.
+    pub fn status(&self) -> Result<(), tokio_executor::SpawnError> {
+        self.0.status()
+    }
+}
+
+impl<T> future::Executor<T> for Handle
+where
+    T: Future<Item = (), Error = ()> + Send + 'static,
+{
+    fn execute(&self, future: T) -> Result<(), future::ExecuteError<T>> {
+        if let Err(e) = self.status() {
+            let kind = if e.is_at_capacity() {
+                future::ExecuteErrorKind::NoCapacity
+            } else {
+                future::ExecuteErrorKind::Shutdown
+            };
+
+            return Err(future::ExecuteError::new(kind, future));
+        }
+
+        let _ = self.spawn(future);
+        Ok(())
+    }
+}
+
+/// Error returned by the `run` function.
+#[derive(Debug)]
+pub struct RunError {
+    inner: current_thread::RunError,
+}
+
+impl fmt::Display for RunError {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        write!(fmt, "{}", self.inner)
+    }
+}
+
+impl Error for RunError {
+    fn description(&self) -> &str {
+        self.inner.description()
+    }
+    fn cause(&self) -> Option<&Error> {
+        self.inner.cause()
+    }
+}
+
+impl Runtime {
+    #[allow(clippy::new_ret_no_self)]
+    /// Returns a new runtime initialized with default configuration values.
+    pub fn new() -> io::Result<Runtime> {
+        Builder::new().build_rt()
+    }
+
+    pub(super) fn new2(
+        reactor_handle: tokio_reactor::Handle,
+        timer_handle: timer::Handle,
+        clock: Clock,
+        executor: CurrentThread<Timer<Reactor>>,
+    ) -> Runtime {
+        Runtime {
+            reactor_handle,
+            timer_handle,
+            clock,
+            executor,
+        }
+    }
+
+    /// Get a new handle to spawn futures on the single-threaded Tokio runtime
+    ///
+    /// Different to the runtime itself, the handle can be sent to different
+    /// threads.
+    pub fn handle(&self) -> Handle {
+        Handle(self.executor.handle().clone())
+    }
+
+    /// Spawn a future onto the single-threaded Tokio runtime.
+    ///
+    /// See [module level][mod] documentation for more details.
+    ///
+    /// [mod]: index.html
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use futures::{future, Future, Stream};
+    /// use actix_rt::Runtime;
+    ///
+    /// # fn dox() {
+    /// // Create the runtime
+    /// let mut rt = Runtime::new().unwrap();
+    ///
+    /// // Spawn a future onto the runtime
+    /// rt.spawn(future::lazy(|| {
+    ///     println!("running on the runtime");
+    ///     Ok(())
+    /// }));
+    /// # }
+    /// # pub fn main() {}
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if the spawn fails. Failure occurs if the executor
+    /// is currently at capacity and is unable to spawn a new future.
+    pub fn spawn<F>(&mut self, future: F) -> &mut Self
+    where
+        F: Future<Item = (), Error = ()> + 'static,
+    {
+        self.executor.spawn(future);
+        self
+    }
+
+    /// Runs the provided future, blocking the current thread until the future
+    /// completes.
+    ///
+    /// This function can be used to synchronously block the current thread
+    /// until the provided `future` has resolved either successfully or with an
+    /// error. The result of the future is then returned from this function
+    /// call.
+    ///
+    /// Note that this function will **also** execute any spawned futures on the
+    /// current thread, but will **not** block until these other spawned futures
+    /// have completed. Once the function returns, any uncompleted futures
+    /// remain pending in the `Runtime` instance. These futures will not run
+    /// until `block_on` or `run` is called again.
+    ///
+    /// The caller is responsible for ensuring that other spawned futures
+    /// complete execution by calling `block_on` or `run`.
+    pub fn block_on<F>(&mut self, f: F) -> Result<F::Item, F::Error>
+    where
+        F: Future,
+    {
+        self.enter(|executor| {
+            // Run the provided future
+            let ret = executor.block_on(f);
+            ret.map_err(|e| e.into_inner().expect("unexpected execution error"))
+        })
+    }
+
+    /// Run the executor to completion, blocking the thread until **all**
+    /// spawned futures have completed.
+    pub fn run(&mut self) -> Result<(), RunError> {
+        self.enter(|executor| executor.run())
+            .map_err(|e| RunError { inner: e })
+    }
+
+    fn enter<F, R>(&mut self, f: F) -> R
+    where
+        F: FnOnce(&mut current_thread::Entered<Timer<Reactor>>) -> R,
+    {
+        let Runtime {
+            ref reactor_handle,
+            ref timer_handle,
+            ref clock,
+            ref mut executor,
+            ..
+        } = *self;
+
+        // Binds an executor to this thread
+        let mut enter = tokio_executor::enter().expect("Multiple executors at once");
+
+        // This will set the default handle and timer to use inside the closure
+        // and run the future.
+        tokio_reactor::with_default(&reactor_handle, &mut enter, |enter| {
+            clock::with_default(clock, enter, |enter| {
+                timer::with_default(&timer_handle, enter, |enter| {
+                    // The TaskExecutor is a fake executor that looks into the
+                    // current single-threaded executor when used. This is a trick,
+                    // because we need two mutable references to the executor (one
+                    // to run the provided future, another to install as the default
+                    // one). We use the fake one here as the default one.
+                    let mut default_executor = current_thread::TaskExecutor::current();
+                    tokio_executor::with_default(&mut default_executor, enter, |enter| {
+                        let mut executor = executor.enter(enter);
+                        f(&mut executor)
+                    })
+                })
+            })
+        })
+    }
+}

actix-rt/src/system.rs

@@ -0,0 +1,119 @@
+use std::cell::RefCell;
+
+use futures::sync::mpsc::UnboundedSender;
+
+use crate::arbiter::{Arbiter, SystemCommand};
+use crate::builder::{Builder, SystemRunner};
+
+/// System is a runtime manager.
+#[derive(Clone, Debug)]
+pub struct System {
+    sys: UnboundedSender<SystemCommand>,
+    arbiter: Arbiter,
+    stop_on_panic: bool,
+}
+
+thread_local!(
+    static CURRENT: RefCell<Option<System>> = RefCell::new(None);
+);
+
+impl System {
+    /// Constructs new system and sets it as current
+    pub(crate) fn construct(
+        sys: UnboundedSender<SystemCommand>,
+        arbiter: Arbiter,
+        stop_on_panic: bool,
+    ) -> Self {
+        let sys = System {
+            sys,
+            arbiter,
+            stop_on_panic,
+        };
+        System::set_current(sys.clone());
+        sys
+    }
+
+    /// Build a new system with a customized tokio runtime.
+    ///
+    /// This allows to customize the runtime. See struct level docs on
+    /// `Builder` for more information.
+    pub fn builder() -> Builder {
+        Builder::new()
+    }
+
+    #[allow(clippy::new_ret_no_self)]
+    /// Create new system.
+    ///
+    /// This method panics if it can not create tokio runtime
+    pub fn new<T: Into<String>>(name: T) -> SystemRunner {
+        Self::builder().name(name).build()
+    }
+
+    /// Get current running system.
+    pub fn current() -> System {
+        CURRENT.with(|cell| match *cell.borrow() {
+            Some(ref sys) => sys.clone(),
+            None => panic!("System is not running"),
+        })
+    }
+
+    /// Set current running system.
+    #[doc(hidden)]
+    pub(crate) fn _is_set() -> bool {
+        CURRENT.with(|cell| cell.borrow().is_some())
+    }
+
+    /// Set current running system.
+    #[doc(hidden)]
+    pub fn set_current(sys: System) {
+        CURRENT.with(|s| {
+            *s.borrow_mut() = Some(sys);
+        })
+    }
+
+    /// Execute function with system reference.
+    pub fn with_current<F, R>(f: F) -> R
+    where
+        F: FnOnce(&System) -> R,
+    {
+        CURRENT.with(|cell| match *cell.borrow() {
+            Some(ref sys) => f(sys),
+            None => panic!("System is not running"),
+        })
+    }
+
+    /// Stop the system
+    pub fn stop(&self) {
+        self.stop_with_code(0)
+    }
+
+    /// Stop the system with a particular exit code.
+    pub fn stop_with_code(&self, code: i32) {
+        let _ = self.sys.unbounded_send(SystemCommand::Exit(code));
+    }
+
+    pub(crate) fn sys(&self) -> &UnboundedSender<SystemCommand> {
+        &self.sys
+    }
+
+    /// Return status of 'stop_on_panic' option which controls whether the System is stopped when an
+    /// uncaught panic is thrown from a worker thread.
+    pub fn stop_on_panic(&self) -> bool {
+        self.stop_on_panic
+    }
+
+    /// System arbiter
+    pub fn arbiter(&self) -> &Arbiter {
+        &self.arbiter
+    }
+
+    /// This function will start tokio runtime and will finish once the
+    /// `System::stop()` message get called.
+    /// Function `f` get called within tokio runtime context.
+    pub fn run<F>(f: F) -> i32
+    where
+        F: FnOnce() + 'static,
+    {
+        Self::builder().run(f)
+    }
+}