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
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
use crate::runtime::handle::Handle;
use crate::runtime::{blocking, driver, Callback, Runtime, Spawner};

use std::fmt;
use std::io;
use std::time::Duration;

/// Builds Tokio Runtime with custom configuration values.
///
/// Methods can be chained in order to set the configuration values. The
/// Runtime is constructed by calling [`build`].
///
/// New instances of `Builder` are obtained via [`Builder::new_multi_thread`]
/// or [`Builder::new_current_thread`].
///
/// See function level documentation for details on the various configuration
/// settings.
///
/// [`build`]: method@Self::build
/// [`Builder::new_multi_thread`]: method@Self::new_multi_thread
/// [`Builder::new_current_thread`]: method@Self::new_current_thread
///
/// # Examples
///
/// ```
/// use tokio::runtime::Builder;
///
/// fn main() {
///     // build runtime
///     let runtime = Builder::new_multi_thread()
///         .worker_threads(4)
///         .thread_name("my-custom-name")
///         .thread_stack_size(3 * 1024 * 1024)
///         .build()
///         .unwrap();
///
///     // use runtime ...
/// }
/// ```
pub struct Builder {
    /// Runtime type
    kind: Kind,

    /// Whether or not to enable the I/O driver
    enable_io: bool,

    /// Whether or not to enable the time driver
    enable_time: bool,

    /// Whether or not the clock should start paused.
    start_paused: bool,

    /// The number of worker threads, used by Runtime.
    ///
    /// Only used when not using the current-thread executor.
    worker_threads: Option<usize>,

    /// Cap on thread usage.
    max_blocking_threads: usize,

    /// Name fn used for threads spawned by the runtime.
    pub(super) thread_name: ThreadNameFn,

    /// Stack size used for threads spawned by the runtime.
    pub(super) thread_stack_size: Option<usize>,

    /// Callback to run after each thread starts.
    pub(super) after_start: Option<Callback>,

    /// To run before each worker thread stops
    pub(super) before_stop: Option<Callback>,

    /// Customizable keep alive timeout for BlockingPool
    pub(super) keep_alive: Option<Duration>,
}

pub(crate) type ThreadNameFn = std::sync::Arc<dyn Fn() -> String + Send + Sync + 'static>;

pub(crate) enum Kind {
    CurrentThread,
    #[cfg(feature = "rt-multi-thread")]
    MultiThread,
}

impl Builder {
    /// Returns a new builder with the current thread scheduler selected.
    ///
    /// Configuration methods can be chained on the return value.
    ///
    /// To spawn non-`Send` tasks on the resulting runtime, combine it with a
    /// [`LocalSet`].
    ///
    /// [`LocalSet`]: crate::task::LocalSet
    pub fn new_current_thread() -> Builder {
        Builder::new(Kind::CurrentThread)
    }

    /// Returns a new builder with the multi thread scheduler selected.
    ///
    /// Configuration methods can be chained on the return value.
    #[cfg(feature = "rt-multi-thread")]
    #[cfg_attr(docsrs, doc(cfg(feature = "rt-multi-thread")))]
    pub fn new_multi_thread() -> Builder {
        Builder::new(Kind::MultiThread)
    }

    /// Returns a new runtime builder initialized with default configuration
    /// values.
    ///
    /// Configuration methods can be chained on the return value.
    pub(crate) fn new(kind: Kind) -> Builder {
        Builder {
            kind,

            // I/O defaults to "off"
            enable_io: false,

            // Time defaults to "off"
            enable_time: false,

            // The clock starts not-paused
            start_paused: false,

            // Default to lazy auto-detection (one thread per CPU core)
            worker_threads: None,

            max_blocking_threads: 512,

            // Default thread name
            thread_name: std::sync::Arc::new(|| "tokio-runtime-worker".into()),

            // Do not set a stack size by default
            thread_stack_size: None,

            // No worker thread callbacks
            after_start: None,
            before_stop: None,

            keep_alive: None,
        }
    }

    /// Enables both I/O and time drivers.
    ///
    /// Doing this is a shorthand for calling `enable_io` and `enable_time`
    /// individually. If additional components are added to Tokio in the future,
    /// `enable_all` will include these future components.
    ///
    /// # Examples
    ///
    /// ```
    /// use tokio::runtime;
    ///
    /// let rt = runtime::Builder::new_multi_thread()
    ///     .enable_all()
    ///     .build()
    ///     .unwrap();
    /// ```
    pub fn enable_all(&mut self) -> &mut Self {
        #[cfg(any(feature = "net", feature = "process", all(unix, feature = "signal")))]
        self.enable_io();
        #[cfg(feature = "time")]
        self.enable_time();

        self
    }

    /// Sets the number of worker threads the `Runtime` will use.
    ///
    /// This can be any number above 0 though it is advised to keep this value
    /// on the smaller side.
    ///
    /// # Default
    ///
    /// The default value is the number of cores available to the system.
    ///
    /// # Panic
    ///
    /// When using the `current_thread` runtime this method will panic, since
    /// those variants do not allow setting worker thread counts.
    ///
    ///
    /// # Examples
    ///
    /// ## Multi threaded runtime with 4 threads
    ///
    /// ```
    /// use tokio::runtime;
    ///
    /// // This will spawn a work-stealing runtime with 4 worker threads.
    /// let rt = runtime::Builder::new_multi_thread()
    ///     .worker_threads(4)
    ///     .build()
    ///     .unwrap();
    ///
    /// rt.spawn(async move {});
    /// ```
    ///
    /// ## Current thread runtime (will only run on the current thread via `Runtime::block_on`)
    ///
    /// ```
    /// use tokio::runtime;
    ///
    /// // Create a runtime that _must_ be driven from a call
    /// // to `Runtime::block_on`.
    /// let rt = runtime::Builder::new_current_thread()
    ///     .build()
    ///     .unwrap();
    ///
    /// // This will run the runtime and future on the current thread
    /// rt.block_on(async move {});
    /// ```
    ///
    /// # Panic
    ///
    /// This will panic if `val` is not larger than `0`.
    pub fn worker_threads(&mut self, val: usize) -> &mut Self {
        assert!(val > 0, "Worker threads cannot be set to 0");
        self.worker_threads = Some(val);
        self
    }

    /// Specifies the limit for additional threads spawned by the Runtime.
    ///
    /// These threads are used for blocking operations like tasks spawned
    /// through [`spawn_blocking`]. Unlike the [`worker_threads`], they are not
    /// always active and will exit if left idle for too long. You can change
    /// this timeout duration with [`thread_keep_alive`].
    ///
    /// The default value is 512.
    ///
    /// # Panic
    ///
    /// This will panic if `val` is not larger than `0`.
    ///
    /// # Upgrading from 0.x
    ///
    /// In old versions `max_threads` limited both blocking and worker threads, but the
    /// current `max_blocking_threads` does not include async worker threads in the count.
    ///
    /// [`spawn_blocking`]: fn@crate::task::spawn_blocking
    /// [`worker_threads`]: Self::worker_threads
    /// [`thread_keep_alive`]: Self::thread_keep_alive
    #[cfg_attr(docsrs, doc(alias = "max_threads"))]
    pub fn max_blocking_threads(&mut self, val: usize) -> &mut Self {
        assert!(val > 0, "Max blocking threads cannot be set to 0");
        self.max_blocking_threads = val;
        self
    }

    /// Sets name of threads spawned by the `Runtime`'s thread pool.
    ///
    /// The default name is "tokio-runtime-worker".
    ///
    /// # Examples
    ///
    /// ```
    /// # use tokio::runtime;
    ///
    /// # pub fn main() {
    /// let rt = runtime::Builder::new_multi_thread()
    ///     .thread_name("my-pool")
    ///     .build();
    /// # }
    /// ```
    pub fn thread_name(&mut self, val: impl Into<String>) -> &mut Self {
        let val = val.into();
        self.thread_name = std::sync::Arc::new(move || val.clone());
        self
    }

    /// Sets a function used to generate the name of threads spawned by the `Runtime`'s thread pool.
    ///
    /// The default name fn is `|| "tokio-runtime-worker".into()`.
    ///
    /// # Examples
    ///
    /// ```
    /// # use tokio::runtime;
    /// # use std::sync::atomic::{AtomicUsize, Ordering};
    ///
    /// # pub fn main() {
    /// let rt = runtime::Builder::new_multi_thread()
    ///     .thread_name_fn(|| {
    ///        static ATOMIC_ID: AtomicUsize = AtomicUsize::new(0);
    ///        let id = ATOMIC_ID.fetch_add(1, Ordering::SeqCst);
    ///        format!("my-pool-{}", id)
    ///     })
    ///     .build();
    /// # }
    /// ```
    pub fn thread_name_fn<F>(&mut self, f: F) -> &mut Self
    where
        F: Fn() -> String + Send + Sync + 'static,
    {
        self.thread_name = std::sync::Arc::new(f);
        self
    }

    /// Sets the stack size (in bytes) for worker threads.
    ///
    /// The actual stack size may be greater than this value if the platform
    /// specifies minimal stack size.
    ///
    /// The default stack size for spawned threads is 2 MiB, though this
    /// particular stack size is subject to change in the future.
    ///
    /// # Examples
    ///
    /// ```
    /// # use tokio::runtime;
    ///
    /// # pub fn main() {
    /// let rt = runtime::Builder::new_multi_thread()
    ///     .thread_stack_size(32 * 1024)
    ///     .build();
    /// # }
    /// ```
    pub fn thread_stack_size(&mut self, val: usize) -> &mut Self {
        self.thread_stack_size = Some(val);
        self
    }

    /// Executes function `f` after each thread is started but before it starts
    /// doing work.
    ///
    /// This is intended for bookkeeping and monitoring use cases.
    ///
    /// # Examples
    ///
    /// ```
    /// # use tokio::runtime;
    ///
    /// # pub fn main() {
    /// let runtime = runtime::Builder::new_multi_thread()
    ///     .on_thread_start(|| {
    ///         println!("thread started");
    ///     })
    ///     .build();
    /// # }
    /// ```
    #[cfg(not(loom))]
    pub fn on_thread_start<F>(&mut self, f: F) -> &mut Self
    where
        F: Fn() + Send + Sync + 'static,
    {
        self.after_start = Some(std::sync::Arc::new(f));
        self
    }

    /// Executes function `f` before each thread stops.
    ///
    /// This is intended for bookkeeping and monitoring use cases.
    ///
    /// # Examples
    ///
    /// ```
    /// # use tokio::runtime;
    ///
    /// # pub fn main() {
    /// let runtime = runtime::Builder::new_multi_thread()
    ///     .on_thread_stop(|| {
    ///         println!("thread stopping");
    ///     })
    ///     .build();
    /// # }
    /// ```
    #[cfg(not(loom))]
    pub fn on_thread_stop<F>(&mut self, f: F) -> &mut Self
    where
        F: Fn() + Send + Sync + 'static,
    {
        self.before_stop = Some(std::sync::Arc::new(f));
        self
    }

    /// Creates the configured `Runtime`.
    ///
    /// The returned `Runtime` instance is ready to spawn tasks.
    ///
    /// # Examples
    ///
    /// ```
    /// use tokio::runtime::Builder;
    ///
    /// let rt  = Builder::new_multi_thread().build().unwrap();
    ///
    /// rt.block_on(async {
    ///     println!("Hello from the Tokio runtime");
    /// });
    /// ```
    pub fn build(&mut self) -> io::Result<Runtime> {
        match &self.kind {
            Kind::CurrentThread => self.build_basic_runtime(),
            #[cfg(feature = "rt-multi-thread")]
            Kind::MultiThread => self.build_threaded_runtime(),
        }
    }

    fn get_cfg(&self) -> driver::Cfg {
        driver::Cfg {
            enable_pause_time: match self.kind {
                Kind::CurrentThread => true,
                #[cfg(feature = "rt-multi-thread")]
                Kind::MultiThread => false,
            },
            enable_io: self.enable_io,
            enable_time: self.enable_time,
            start_paused: self.start_paused,
        }
    }

    /// Sets a custom timeout for a thread in the blocking pool.
    ///
    /// By default, the timeout for a thread is set to 10 seconds. This can
    /// be overriden using .thread_keep_alive().
    ///
    /// # Example
    ///
    /// ```
    /// # use tokio::runtime;
    /// # use std::time::Duration;
    ///
    /// # pub fn main() {
    /// let rt = runtime::Builder::new_multi_thread()
    ///     .thread_keep_alive(Duration::from_millis(100))
    ///     .build();
    /// # }
    /// ```
    pub fn thread_keep_alive(&mut self, duration: Duration) -> &mut Self {
        self.keep_alive = Some(duration);
        self
    }

    fn build_basic_runtime(&mut self) -> io::Result<Runtime> {
        use crate::runtime::{BasicScheduler, Kind};

        let (driver, resources) = driver::Driver::new(self.get_cfg())?;

        // And now put a single-threaded scheduler 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 scheduler = BasicScheduler::new(driver);
        let spawner = Spawner::Basic(scheduler.spawner().clone());

        // Blocking pool
        let blocking_pool = blocking::create_blocking_pool(self, self.max_blocking_threads);
        let blocking_spawner = blocking_pool.spawner().clone();

        Ok(Runtime {
            kind: Kind::CurrentThread(scheduler),
            handle: Handle {
                spawner,
                io_handle: resources.io_handle,
                time_handle: resources.time_handle,
                signal_handle: resources.signal_handle,
                clock: resources.clock,
                blocking_spawner,
            },
            blocking_pool,
        })
    }
}

cfg_io_driver! {
    impl Builder {
        /// Enables the I/O driver.
        ///
        /// Doing this enables using net, process, signal, and some I/O types on
        /// the runtime.
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::runtime;
        ///
        /// let rt = runtime::Builder::new_multi_thread()
        ///     .enable_io()
        ///     .build()
        ///     .unwrap();
        /// ```
        pub fn enable_io(&mut self) -> &mut Self {
            self.enable_io = true;
            self
        }
    }
}

cfg_time! {
    impl Builder {
        /// Enables the time driver.
        ///
        /// Doing this enables using `tokio::time` on the runtime.
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::runtime;
        ///
        /// let rt = runtime::Builder::new_multi_thread()
        ///     .enable_time()
        ///     .build()
        ///     .unwrap();
        /// ```
        pub fn enable_time(&mut self) -> &mut Self {
            self.enable_time = true;
            self
        }
    }
}

cfg_test_util! {
    impl Builder {
        /// Controls if the runtime's clock starts paused or advancing.
        ///
        /// Pausing time requires the current-thread runtime; construction of
        /// the runtime will panic otherwise.
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::runtime;
        ///
        /// let rt = runtime::Builder::new_current_thread()
        ///     .enable_time()
        ///     .start_paused(true)
        ///     .build()
        ///     .unwrap();
        /// ```
        pub fn start_paused(&mut self, start_paused: bool) -> &mut Self {
            self.start_paused = start_paused;
            self
        }
    }
}

cfg_rt_multi_thread! {
    impl Builder {
        fn build_threaded_runtime(&mut self) -> io::Result<Runtime> {
            use crate::loom::sys::num_cpus;
            use crate::runtime::{Kind, ThreadPool};
            use crate::runtime::park::Parker;

            let core_threads = self.worker_threads.unwrap_or_else(num_cpus);

            let (driver, resources) = driver::Driver::new(self.get_cfg())?;

            let (scheduler, launch) = ThreadPool::new(core_threads, Parker::new(driver));
            let spawner = Spawner::ThreadPool(scheduler.spawner().clone());

            // Create the blocking pool
            let blocking_pool = blocking::create_blocking_pool(self, self.max_blocking_threads + core_threads);
            let blocking_spawner = blocking_pool.spawner().clone();

            // Create the runtime handle
            let handle = Handle {
                spawner,
                io_handle: resources.io_handle,
                time_handle: resources.time_handle,
                signal_handle: resources.signal_handle,
                clock: resources.clock,
                blocking_spawner,
            };

            // Spawn the thread pool workers
            let _enter = crate::runtime::context::enter(handle.clone());
            launch.launch();

            Ok(Runtime {
                kind: Kind::ThreadPool(scheduler),
                handle,
                blocking_pool,
            })
        }
    }
}

impl fmt::Debug for Builder {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_struct("Builder")
            .field("worker_threads", &self.worker_threads)
            .field("max_blocking_threads", &self.max_blocking_threads)
            .field(
                "thread_name",
                &"<dyn Fn() -> String + Send + Sync + 'static>",
            )
            .field("thread_stack_size", &self.thread_stack_size)
            .field("after_start", &self.after_start.as_ref().map(|_| "..."))
            .field("before_stop", &self.after_start.as_ref().map(|_| "..."))
            .finish()
    }
}