nautilus_common/live/
timer.rs

1// -------------------------------------------------------------------------------------------------
2//  Copyright (C) 2015-2026 Nautech Systems Pty Ltd. All rights reserved.
3//  https://nautechsystems.io
4//
5//  Licensed under the GNU Lesser General Public License Version 3.0 (the "License");
6//  You may not use this file except in compliance with the License.
7//  You may obtain a copy of the License at https://www.gnu.org/licenses/lgpl-3.0.en.html
8//
9//  Unless required by applicable law or agreed to in writing, software
10//  distributed under the License is distributed on an "AS IS" BASIS,
11//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12//  See the License for the specific language governing permissions and
13//  limitations under the License.
14// -------------------------------------------------------------------------------------------------
15
16//! Live timer implementation using Tokio for real-time scheduling.
17
18use std::{
19    num::NonZeroU64,
20    sync::{
21        Arc,
22        atomic::{self, AtomicU64},
23    },
24};
25
26use nautilus_core::{
27    UUID4, UnixNanos,
28    correctness::{FAILED, check_valid_string_utf8},
29    datetime::floor_to_nearest_microsecond,
30    time::get_atomic_clock_realtime,
31};
32#[cfg(feature = "python")]
33use pyo3::{Py, PyAny, Python};
34use tokio::{
35    task::JoinHandle,
36    time::{Duration, Instant},
37};
38use ustr::Ustr;
39
40use super::runtime::get_runtime;
41use crate::{
42    runner::TimeEventSender,
43    timer::{TimeEvent, TimeEventCallback, TimeEventHandlerV2},
44};
45
46/// A live timer for use with a `LiveClock`.
47///
48/// `LiveTimer` triggers events at specified intervals in a real-time environment,
49/// using Tokio's async runtime to handle scheduling and execution.
50///
51/// # Threading
52///
53/// The timer runs on the runtime thread that created it and dispatches events across threads as needed.
54#[derive(Debug)]
55pub struct LiveTimer {
56    /// The name of the timer.
57    pub name: Ustr,
58    /// The start time of the timer in UNIX nanoseconds.
59    pub interval_ns: NonZeroU64,
60    /// The start time of the timer in UNIX nanoseconds.
61    pub start_time_ns: UnixNanos,
62    /// The optional stop time of the timer in UNIX nanoseconds.
63    pub stop_time_ns: Option<UnixNanos>,
64    /// If the timer should fire immediately at start time.
65    pub fire_immediately: bool,
66    next_time_ns: Arc<AtomicU64>,
67    callback: TimeEventCallback,
68    task_handle: Option<JoinHandle<()>>,
69    sender: Option<Arc<dyn TimeEventSender>>,
70}
71
72impl LiveTimer {
73    /// Creates a new [`LiveTimer`] instance.
74    ///
75    /// # Panics
76    ///
77    /// Panics if `name` is not a valid string.
78    #[allow(clippy::too_many_arguments)]
79    #[must_use]
80    pub fn new(
81        name: Ustr,
82        interval_ns: NonZeroU64,
83        start_time_ns: UnixNanos,
84        stop_time_ns: Option<UnixNanos>,
85        callback: TimeEventCallback,
86        fire_immediately: bool,
87        sender: Option<Arc<dyn TimeEventSender>>,
88    ) -> Self {
89        check_valid_string_utf8(name, stringify!(name)).expect(FAILED);
90
91        let next_time_ns = if fire_immediately {
92            start_time_ns.as_u64()
93        } else {
94            start_time_ns.as_u64() + interval_ns.get()
95        };
96
97        log::debug!("Creating timer '{name}'");
98
99        Self {
100            name,
101            interval_ns,
102            start_time_ns,
103            stop_time_ns,
104            fire_immediately,
105            next_time_ns: Arc::new(AtomicU64::new(next_time_ns)),
106            callback,
107            task_handle: None,
108            sender,
109        }
110    }
111
112    /// Returns the next time in UNIX nanoseconds when the timer will fire.
113    ///
114    /// Provides the scheduled time for the next event based on the current state of the timer.
115    #[must_use]
116    pub fn next_time_ns(&self) -> UnixNanos {
117        UnixNanos::from(self.next_time_ns.load(atomic::Ordering::SeqCst))
118    }
119
120    /// Returns whether the timer is expired.
121    ///
122    /// An expired timer will not trigger any further events.
123    /// A timer that has not been started is not expired.
124    #[must_use]
125    pub fn is_expired(&self) -> bool {
126        self.task_handle
127            .as_ref()
128            .is_some_and(tokio::task::JoinHandle::is_finished)
129    }
130
131    /// Starts the timer.
132    ///
133    /// Time events will begin triggering at the specified intervals.
134    /// The generated events are handled by the provided callback function.
135    ///
136    /// # Panics
137    ///
138    /// Panics if using a Rust callback (`Rust` or `RustLocal`) without a `TimeEventSender`.
139    #[allow(unused_variables)]
140    pub fn start(&mut self) {
141        let event_name = self.name;
142        let stop_time_ns = self.stop_time_ns;
143        let interval_ns = self.interval_ns.get();
144        let callback = self.callback.clone();
145
146        // Get current time
147        let clock = get_atomic_clock_realtime();
148        let now_ns = clock.get_time_ns();
149
150        // Check if the timer's alert time is in the past and adjust if needed
151        let now_raw = now_ns.as_u64();
152        let mut observed_next = self.next_time_ns.load(atomic::Ordering::SeqCst);
153
154        if observed_next <= now_raw {
155            loop {
156                match self.next_time_ns.compare_exchange(
157                    observed_next,
158                    now_raw,
159                    atomic::Ordering::SeqCst,
160                    atomic::Ordering::SeqCst,
161                ) {
162                    Ok(_) => {
163                        if observed_next < now_raw {
164                            let original = UnixNanos::from(observed_next);
165                            log::warn!(
166                                "Timer '{event_name}' alert time {} was in the past, adjusted to current time for immediate fire",
167                                original.to_rfc3339(),
168                            );
169                        }
170                        observed_next = now_raw;
171                        break;
172                    }
173                    Err(actual) => {
174                        observed_next = actual;
175                        if observed_next > now_raw {
176                            break;
177                        }
178                    }
179                }
180            }
181        }
182
183        // Floor the next time to the nearest microsecond which is within the timers accuracy
184        let mut next_time_ns = UnixNanos::from(floor_to_nearest_microsecond(observed_next));
185        let next_time_atomic = self.next_time_ns.clone();
186        next_time_atomic.store(next_time_ns.as_u64(), atomic::Ordering::SeqCst);
187
188        let sender = self.sender.clone();
189
190        let rt = get_runtime();
191        let handle = rt.spawn(async move {
192            let clock = get_atomic_clock_realtime();
193
194            // 1-millisecond delay to account for the overhead of initializing a tokio timer
195            let overhead = Duration::from_millis(1);
196            let delay_ns = next_time_ns.saturating_sub(now_ns.as_u64());
197            let mut delay = Duration::from_nanos(delay_ns);
198
199            // Subtract the estimated startup overhead; saturating to zero for sub-ms delays
200            if delay > overhead {
201                delay -= overhead;
202            } else {
203                delay = Duration::from_nanos(0);
204            }
205
206            let start = Instant::now() + delay;
207
208            let mut timer = tokio::time::interval_at(start, Duration::from_nanos(interval_ns));
209
210            loop {
211                // SAFETY: `timer.tick` is cancellation safe, if the cancel branch completes
212                // first then no tick has been consumed (no event was ready).
213                timer.tick().await;
214                let now_ns = clock.get_time_ns();
215
216                let event = TimeEvent::new(event_name, UUID4::new(), next_time_ns, now_ns);
217
218                match callback {
219                    #[cfg(feature = "python")]
220                    TimeEventCallback::Python(ref callback) => {
221                        call_python_with_time_event(event, callback);
222                    }
223                    TimeEventCallback::Rust(_) | TimeEventCallback::RustLocal(_) => {
224                        debug_assert!(
225                            sender.is_some(),
226                            "LiveTimer with Rust callback requires TimeEventSender"
227                        );
228                        let sender = sender
229                            .as_ref()
230                            .expect("timer event sender was unset for Rust callback system");
231                        let handler = TimeEventHandlerV2::new(event, callback.clone());
232                        sender.send(handler);
233                    }
234                }
235
236                // Prepare next time interval
237                next_time_ns += interval_ns;
238                next_time_atomic.store(next_time_ns.as_u64(), atomic::Ordering::SeqCst);
239
240                // Check if expired
241                if let Some(stop_time_ns) = stop_time_ns
242                    && std::cmp::max(next_time_ns, now_ns) >= stop_time_ns
243                {
244                    break; // Timer expired
245                }
246            }
247        });
248
249        self.task_handle = Some(handle);
250    }
251
252    /// Cancels the timer.
253    ///
254    /// The timer will not generate a final event.
255    pub fn cancel(&mut self) {
256        log::debug!("Cancel timer '{}'", self.name);
257        if let Some(ref handle) = self.task_handle {
258            handle.abort();
259        }
260    }
261}
262
263#[cfg(feature = "python")]
264fn call_python_with_time_event(event: TimeEvent, callback: &Py<PyAny>) {
265    use nautilus_core::python::IntoPyObjectNautilusExt;
266    use pyo3::types::PyCapsule;
267
268    Python::attach(|py| {
269        // Create a new PyCapsule that owns `event` and registers a destructor so
270        // the contained `TimeEvent` is properly freed once the capsule is
271        // garbage-collected by Python. Without the destructor the memory would
272        // leak because the capsule would not know how to drop the Rust value.
273
274        // Register a destructor that simply drops the `TimeEvent` once the
275        // capsule is freed on the Python side.
276        let capsule: Py<PyAny> = PyCapsule::new_with_destructor(py, event, None, |_, _| {})
277            .expect("Error creating `PyCapsule`")
278            .into_py_any_unwrap(py);
279
280        match callback.call1(py, (capsule,)) {
281            Ok(_) => {}
282            Err(e) => tracing::error!("Error on callback: {e:?}"),
283        }
284    });
285}
286
287#[cfg(test)]
288mod tests {
289    use std::{num::NonZeroU64, sync::Arc};
290
291    use nautilus_core::{UnixNanos, time::get_atomic_clock_realtime};
292    use rstest::*;
293    use ustr::Ustr;
294
295    use super::LiveTimer;
296    use crate::{
297        runner::TimeEventSender,
298        timer::{TimeEventCallback, TimeEventHandlerV2},
299    };
300
301    #[rstest]
302    fn test_live_timer_fire_immediately_field() {
303        let timer = LiveTimer::new(
304            Ustr::from("TEST_TIMER"),
305            NonZeroU64::new(1000).unwrap(),
306            UnixNanos::from(100),
307            None,
308            TimeEventCallback::from(|_| {}),
309            true, // fire_immediately = true
310            None, // time_event_sender
311        );
312
313        // Verify the field is set correctly
314        assert!(timer.fire_immediately);
315
316        // With fire_immediately=true, next_time_ns should be start_time_ns
317        assert_eq!(timer.next_time_ns(), UnixNanos::from(100));
318    }
319
320    #[rstest]
321    fn test_live_timer_fire_immediately_false_field() {
322        let timer = LiveTimer::new(
323            Ustr::from("TEST_TIMER"),
324            NonZeroU64::new(1000).unwrap(),
325            UnixNanos::from(100),
326            None,
327            TimeEventCallback::from(|_| {}),
328            false, // fire_immediately = false
329            None,  // time_event_sender
330        );
331
332        // Verify the field is set correctly
333        assert!(!timer.fire_immediately);
334
335        // With fire_immediately=false, next_time_ns should be start_time_ns + interval
336        assert_eq!(timer.next_time_ns(), UnixNanos::from(1100));
337    }
338
339    #[rstest]
340    fn test_live_timer_adjusts_past_due_start_time() {
341        #[derive(Debug)]
342        struct NoopSender;
343
344        impl TimeEventSender for NoopSender {
345            fn send(&self, _handler: TimeEventHandlerV2) {}
346        }
347
348        let sender = Arc::new(NoopSender);
349        let mut timer = LiveTimer::new(
350            Ustr::from("PAST_TIMER"),
351            NonZeroU64::new(1).unwrap(),
352            UnixNanos::from(0),
353            None,
354            TimeEventCallback::from(|_| {}),
355            true,
356            Some(sender),
357        );
358
359        let before = get_atomic_clock_realtime().get_time_ns();
360
361        timer.start();
362
363        assert!(timer.next_time_ns() >= before);
364
365        timer.cancel();
366    }
367}
nautilus_common/live/timer.rs

nautilus_common/live/
timer.rs
