1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
use pool::{self, Pool, Lifecycle, MAX_FUTURES};
use task::Task;

use std::sync::Arc;
use std::sync::atomic::Ordering::{AcqRel, Acquire};

use tokio_executor::{self, SpawnError};
use futures::{future, Future};
#[cfg(feature = "unstable-futures")]
use futures2;
#[cfg(feature = "unstable-futures")]
use futures2_wake::{into_waker, Futures2Wake};

/// Submit futures to the associated thread pool for execution.
///
/// A `Sender` instance is a handle to a single thread pool, allowing the owner
/// of the handle to spawn futures onto the thread pool. New futures are spawned
/// using [`Sender::spawn`].
///
/// The `Sender` handle is *only* used for spawning new futures. It does not
/// impact the lifecycle of the thread pool in any way.
///
/// `Sender` instances are obtained by calling [`ThreadPool::sender`]. The
/// `Sender` struct implements the `Executor` trait.
///
/// [`Sender::spawn`]: #method.spawn
/// [`ThreadPool::sender`]: struct.ThreadPool.html#method.sender
#[derive(Debug)]
pub struct Sender {
    pub(crate) inner: Arc<Pool>,
}

impl Sender {
    /// Spawn a future onto the thread pool
    ///
    /// This function takes ownership of the future and spawns it onto the
    /// thread pool, assigning it to a worker thread. The exact strategy used to
    /// assign a future to a worker depends on if the caller is already on a
    /// worker thread or external to the thread pool.
    ///
    /// If the caller is currently on the thread pool, the spawned future will
    /// be assigned to the same worker that the caller is on. If the caller is
    /// external to the thread pool, the future will be assigned to a random
    /// worker.
    ///
    /// If `spawn` returns `Ok`, this does not mean that the future will be
    /// executed. The thread pool can be forcibly shutdown between the time
    /// `spawn` is called and the future has a chance to execute.
    ///
    /// If `spawn` returns `Err`, then the future failed to be spawned. There
    /// are two possible causes:
    ///
    /// * The thread pool is at capacity and is unable to spawn a new future.
    ///   This is a temporary failure. At some point in the future, the thread
    ///   pool might be able to spawn new futures.
    /// * The thread pool is shutdown. This is a permanent failure indicating
    ///   that the handle will never be able to spawn new futures.
    ///
    /// The status of the thread pool can be queried before calling `spawn`
    /// using the `status` function (part of the `Executor` trait).
    ///
    /// # Examples
    ///
    /// ```rust
    /// # extern crate tokio_threadpool;
    /// # extern crate futures;
    /// # use tokio_threadpool::ThreadPool;
    /// use futures::future::{Future, lazy};
    ///
    /// # pub fn main() {
    /// // Create a thread pool with default configuration values
    /// let thread_pool = ThreadPool::new();
    ///
    /// thread_pool.sender().spawn(lazy(|| {
    ///     println!("called from a worker thread");
    ///     Ok(())
    /// })).unwrap();
    ///
    /// // Gracefully shutdown the threadpool
    /// thread_pool.shutdown().wait().unwrap();
    /// # }
    /// ```
    pub fn spawn<F>(&self, future: F) -> Result<(), SpawnError>
    where F: Future<Item = (), Error = ()> + Send + 'static,
    {
        let mut s = self;
        tokio_executor::Executor::spawn(&mut s, Box::new(future))
    }

    /// Logic to prepare for spawning
    fn prepare_for_spawn(&self) -> Result<(), SpawnError> {
        let mut state: pool::State = self.inner.state.load(Acquire).into();

        // Increment the number of futures spawned on the pool as well as
        // validate that the pool is still running/
        loop {
            let mut next = state;

            if next.num_futures() == MAX_FUTURES {
                // No capacity
                return Err(SpawnError::at_capacity());
            }

            if next.lifecycle() == Lifecycle::ShutdownNow {
                // Cannot execute the future, executor is shutdown.
                return Err(SpawnError::shutdown());
            }

            next.inc_num_futures();

            let actual = self.inner.state.compare_and_swap(
                state.into(), next.into(), AcqRel).into();

            if actual == state {
                trace!("execute; count={:?}", next.num_futures());
                break;
            }

            state = actual;
        }

        Ok(())
    }
}

impl tokio_executor::Executor for Sender {
    fn status(&self) -> Result<(), tokio_executor::SpawnError> {
        let s = self;
        tokio_executor::Executor::status(&s)
    }

    fn spawn(&mut self, future: Box<Future<Item = (), Error = ()> + Send>)
        -> Result<(), SpawnError>
    {
        let mut s = &*self;
        tokio_executor::Executor::spawn(&mut s, future)
    }

    #[cfg(feature = "unstable-futures")]
    fn spawn2(&mut self, f: Task2) -> Result<(), futures2::executor::SpawnError> {
        futures2::executor::Executor::spawn(self, f)
    }
}

impl<'a> tokio_executor::Executor for &'a Sender {
    fn status(&self) -> Result<(), tokio_executor::SpawnError> {
        let state: pool::State = self.inner.state.load(Acquire).into();

        if state.num_futures() == MAX_FUTURES {
            // No capacity
            return Err(SpawnError::at_capacity());
        }

        if state.lifecycle() == Lifecycle::ShutdownNow {
            // Cannot execute the future, executor is shutdown.
            return Err(SpawnError::shutdown());
        }

        Ok(())
    }

    fn spawn(&mut self, future: Box<Future<Item = (), Error = ()> + Send>)
        -> Result<(), SpawnError>
    {
        self.prepare_for_spawn()?;

        // At this point, the pool has accepted the future, so schedule it for
        // execution.

        // Create a new task for the future
        let task = Arc::new(Task::new(future));

        self.inner.submit(task, &self.inner);

        Ok(())
    }

    #[cfg(feature = "unstable-futures")]
    fn spawn2(&mut self, f: Task2) -> Result<(), futures2::executor::SpawnError> {
        futures2::executor::Executor::spawn(self, f)
    }
}

impl<T> future::Executor<T> for Sender
where T: Future<Item = (), Error = ()> + Send + 'static,
{
    fn execute(&self, future: T) -> Result<(), future::ExecuteError<T>> {
        if let Err(e) = tokio_executor::Executor::status(self) {
            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(())
    }
}

#[cfg(feature = "unstable-futures")]
type Task2 = Box<futures2::Future<Item = (), Error = futures2::Never> + Send>;

#[cfg(feature = "unstable-futures")]
impl futures2::executor::Executor for Sender {
    fn spawn(&mut self, f: Task2) -> Result<(), futures2::executor::SpawnError> {
        let mut s = &*self;
        futures2::executor::Executor::spawn(&mut s, f)
    }

    fn status(&self) -> Result<(), futures2::executor::SpawnError> {
        let s = &*self;
        futures2::executor::Executor::status(&s)
    }
}

#[cfg(feature = "unstable-futures")]
impl<'a> futures2::executor::Executor for &'a Sender {
    fn spawn(&mut self, f: Task2) -> Result<(), futures2::executor::SpawnError> {
        self.prepare_for_spawn()
            // TODO: get rid of this once the futures crate adds more error types
            .map_err(|_| futures2::executor::SpawnError::shutdown())?;

        // At this point, the pool has accepted the future, so schedule it for
        // execution.

        // Create a new task for the future
        let task = Task::new2(f, |id| into_waker(Arc::new(Futures2Wake::new(id, &self.inner))));

        self.inner.submit(task, &self.inner);

        Ok(())
    }

    fn status(&self) -> Result<(), futures2::executor::SpawnError> {
        tokio_executor::Executor::status(self)
        // TODO: get rid of this once the futures crate adds more error types
            .map_err(|_| futures2::executor::SpawnError::shutdown())
    }
}

impl Clone for Sender {
    #[inline]
    fn clone(&self) -> Sender {
        let inner = self.inner.clone();
        Sender { inner }
    }
}