feat(cron) implement Deno.cron() (#21019)

This PR adds unstable `Deno.cron` API to trigger execution of cron jobs.

* State: All cron state is in memory. Cron jobs are scheduled according
to the cron schedule expression and the current time. No state is
persisted to disk.
* Time zone: Cron expressions specify time in UTC.
* Overlapping executions: not permitted. If the next scheduled execution
time occurs while the same cron job is still executing, the scheduled
execution is skipped.
* Retries: failed jobs are automatically retried until they succeed or
until retry threshold is reached. Retry policy can be optionally
specified using `options.backoffSchedule`.

1 files changed, 23 insertions, 0 deletions

diff --git a/ext/cron/interface.rs b/ext/cron/interface.rs
new file mode 100644
index 000000000..c70988788
--- /dev/null
+++ b/ext/cron/interface.rs
@@ -0,0 +1,23 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+
+use async_trait::async_trait;
+use deno_core::error::AnyError;
+
+pub trait CronHandler {
+  type EH: CronHandle + 'static;
+
+  fn create(&self, spec: CronSpec) -> Result<Self::EH, AnyError>;
+}
+
+#[async_trait(?Send)]
+pub trait CronHandle {
+  async fn next(&self, prev_success: bool) -> Result<bool, AnyError>;
+  fn close(&self);
+}
+
+#[derive(Clone)]
+pub struct CronSpec {
+  pub name: String,
+  pub cron_schedule: String,
+  pub backoff_schedule: Option<Vec<u32>>,
+}