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//! Background task scheduler for recurring cron-based jobs.
//!
//! For durable, persistent work use [`crate::jobs`] instead. This scheduler
//! is in-memory only and does not survive process restarts.
use std::sync::Arc;
use tokio_cron_scheduler::{Job, JobScheduler};
use tokio_util::sync::CancellationToken;
#[derive(Debug)]
pub struct CronSchedulerError {
pub cron_schedule: String,
pub error_message: String,
}
impl std::fmt::Display for CronSchedulerError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(
f,
"Failed to create cron job for schedule '{}': {}",
self.cron_schedule, self.error_message
)
}
}
impl std::error::Error for CronSchedulerError {}
/// A background job scheduler that wraps `tokio_cron_scheduler::JobScheduler`.
pub struct CronScheduler {
jobs: Vec<Job>,
scheduler: Option<JobScheduler>,
cancellation_token: CancellationToken,
started: bool,
}
impl Default for CronScheduler {
fn default() -> Self {
Self::new()
}
}
impl CronScheduler {
/// Create a new CronScheduler.
pub fn new() -> Self {
Self {
jobs: Vec::new(),
scheduler: None,
cancellation_token: CancellationToken::new(),
started: false,
}
}
/// Schedules a new background task to be executed according to the provided configuration.
///
/// The task must be an asynchronous closure or function that returns a `Result<(), E>` where `E` implements `std::error::Error`.
/// If the scheduled task returns an error, it will be automatically logged.
///
/// In case blocking code is executed in `task`, the task can _not_ be
/// interrupted automatically and will continue to execute even after a shutdown signal was received.
/// The reason is that Rust async cancellation is cooperative. Tokio cannot forcefully kill an OS thread.
/// Tokio must wait for the code to hit an .await point to check if it should cancel the task.
/// Because there are no .await points during the blocking `task`, the task never yields.
///
/// For graceful shutdown semantics to work as expected, make sure to not run blocking code as part of `task`.
pub fn schedule<F, Fut, E>(
&mut self,
cron_schedule: String,
task: F,
) -> Result<(), CronSchedulerError>
where
F: Fn() -> Fut + Send + Sync + 'static,
Fut: Future<Output = Result<(), E>> + Send + 'static,
E: std::error::Error + Send + 'static,
{
//Wrap task function in an Arc so it can be safely cloned for every cron tick
let task = Arc::new(task);
// Clone main cancellation token
let cronjob_cancellation_token = self.cancellation_token.clone();
let job = Job::new_async(&cron_schedule, move |_uuid, _l| {
let cronjob_cancellation_token = cronjob_cancellation_token.clone();
let task = task.clone();
Box::pin(async move {
tokio::select! {
_ = cronjob_cancellation_token.cancelled() => {
tracing::info!("Shutdown signal received, stopping job scheduler");
}
result = task() => {
if let Err(e) = result {
tracing::error!("Error while running Rapina background job: {}", e);
}
}
}
})
})
.map_err(|error| CronSchedulerError {
cron_schedule: cron_schedule.clone(),
error_message: error.to_string(),
})?;
let job_uuid = job.guid();
// Store the Job synchronously for later
self.jobs.push(job);
tracing::debug!(
"Added cron job with uuid '{}' and schedule '{}' to cron job queue",
job_uuid,
&cron_schedule
);
Ok(())
}
/// Starts the scheduler
///
/// # Panics
///
/// Panics if the underlying `JobScheduler` fails to start.
pub async fn start(&mut self) {
let scheduler = JobScheduler::new()
.await
.expect("Failed to create cronjob scheduler");
for job in self.jobs.drain(..) {
scheduler
.add(job)
.await
.expect("Failed to schedule Rapina background job");
}
scheduler
.start()
.await
.expect("Failed to start Rapina background job scheduler");
self.scheduler = Some(scheduler);
self.started = true;
tracing::info!("Started Rapina background job scheduler");
}
/// Initiates a graceful shutdown of the scheduler and its running tasks.
///
/// This method triggers the `CancellationToken` to notify all currently running tasks to stop.
/// It then shuts down the underlying `JobScheduler`.
///
/// # Panics
///
/// Panics if the underlying `JobScheduler` fails to shut down properly.
pub async fn shutdown(&mut self) {
// instantly trigger all tokio::select! branches that watch the token cancellation, stopping the execution immediately in case no blocking code is being executed
self.cancellation_token.cancel();
if let Some(mut scheduler) = self.scheduler.take() {
scheduler
.shutdown()
.await
.expect("Failed to shutdown Rapina background jobs");
}
tracing::info!(
"Cron scheduler stopped. Blocking tasks may still be in-flight and will keep the process alive until complete."
);
}
/// Returns the number of scheduled jobs, which have not yet been drained by starting the cron scheduler
#[cfg(test)]
pub(crate) fn len(&self) -> usize {
self.jobs.len()
}
/// Returns whether the list of scheduled jobs, which have not yet been drained by starting the cron scheduler, is empty
#[cfg(test)]
fn is_empty(&self) -> bool {
self.jobs.is_empty()
}
/// Returns whether the cron scheduler has been started
#[cfg(test)]
fn is_started(&self) -> bool {
self.started
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::error::Error;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::time::Duration;
#[test]
fn test_new_scheduler_is_empty() {
let scheduler = CronScheduler::new();
assert!(scheduler.jobs.is_empty());
assert!(scheduler.scheduler.is_none());
assert!(!scheduler.cancellation_token.is_cancelled());
}
#[test]
fn test_schedule_adds_job_to_vec_synchronously() {
let mut scheduler = CronScheduler::new();
let result = scheduler.schedule("1/1 * * * * *".to_string(), || async {
Ok::<(), Error>(())
});
assert!(result.is_ok());
assert_eq!(scheduler.jobs.len(), 1);
assert!(scheduler.scheduler.is_none()); // Scheduler should not be created yet
}
#[test]
fn test_schedule_errors_on_bad_input() {
let mut scheduler = CronScheduler::new();
let broken_schedule = "";
let result = scheduler.schedule(broken_schedule.to_string(), || async {
Ok::<(), Error>(())
});
assert!(result.is_err());
assert_eq!(scheduler.jobs.len(), 0);
assert!(scheduler.scheduler.is_none()); // Scheduler should not be created yet
}
#[tokio::test]
async fn test_start_creates_and_empties_jobs() {
let mut scheduler = CronScheduler::new();
scheduler
.schedule("1/1 * * * * *".to_string(), || async {
Ok::<(), Error>(())
})
.unwrap();
scheduler
.schedule("1/2 * * * * *".to_string(), || async {
Ok::<(), Error>(())
})
.unwrap();
assert_eq!(scheduler.jobs.len(), 2);
// Start the scheduler
scheduler.start().await;
// Jobs should be moved into the underlying JobScheduler
assert!(scheduler.jobs.is_empty());
assert!(scheduler.scheduler.is_some());
}
#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn test_cron_execution_and_shutdown() {
let mut scheduler = CronScheduler::new();
let counter = Arc::new(AtomicUsize::new(0));
let counter_clone = counter.clone();
// Schedule a job that runs every second
scheduler
.schedule("*/1 * * * * *".to_string(), move || {
let counter = counter_clone.clone();
async move {
counter.fetch_add(1, Ordering::SeqCst);
Ok::<(), Error>(())
}
})
.unwrap();
scheduler.start().await;
// Wait a little over 2 seconds to ensure the cron ticks at least twice
tokio::time::sleep(Duration::from_millis(2200)).await;
let executions_before_shutdown = counter.load(Ordering::SeqCst);
assert!(
executions_before_shutdown >= 2,
"Expected at least 2 executions, got {}",
executions_before_shutdown
);
// Initiate graceful shutdown
scheduler.shutdown().await;
assert!(scheduler.cancellation_token.is_cancelled());
// Wait another 2 seconds to ensure no more ticks occur after shutdown
tokio::time::sleep(Duration::from_millis(2200)).await;
let executions_after_shutdown = counter.load(Ordering::SeqCst);
// The counter should not have incremented significantly after shutdown.
// Depending on exact timing, 1 extra tick might sneak in during the shutdown process,
// but it shouldn't jump by 2.
assert!(
executions_after_shutdown - executions_before_shutdown <= 1,
"Job continued executing after shutdown! Before: {}, After: {}",
executions_before_shutdown,
executions_after_shutdown
);
}
#[test]
fn test_is_empty_after_scheduling() {
let mut scheduler = CronScheduler::new();
scheduler
.schedule("1/1 * * * * *".to_string(), || async {
Ok::<(), Error>(())
})
.unwrap();
assert!(
!scheduler.is_empty(),
"Scheduler should not be empty after a job is added"
);
}
#[test]
fn test_len_increments_with_jobs() {
let mut scheduler = CronScheduler::new();
scheduler
.schedule("1/1 * * * * *".to_string(), || async {
Ok::<(), Error>(())
})
.unwrap();
assert_eq!(scheduler.len(), 1);
scheduler
.schedule("1/2 * * * * *".to_string(), || async {
Ok::<(), Error>(())
})
.unwrap();
assert_eq!(scheduler.len(), 2);
}
#[tokio::test]
async fn test_is_started_becomes_true_after_start() {
let mut scheduler = CronScheduler::new();
scheduler.start().await;
assert!(
scheduler.is_started(),
"Scheduler must be marked as started after calling start()"
);
}
}