Fix potentially panicing unchecked duration adds in runtime

kube-runtime/src/controller/mod.rs

@@ -472,7 +472,9 @@ where
                     obj_ref,
                     reason: reschedule_reason,
                 },
-                run_at: reconciler_finished_at + requeue_after,
+                run_at: reconciler_finished_at
+                    .checked_add(requeue_after)
+                    .unwrap_or_else(crate::scheduler::far_future),
             }),
             result: Some(result),
         }

kube-runtime/src/scheduler.rs

@@ -74,16 +74,19 @@
             // Message is already pending, so we can't even expedite it
             return;
         }
+        let next_time = request
+            .run_at
+            .checked_add(*self.debounce)
+            .unwrap_or_else(far_future);
         match self.scheduled.entry(request.message) {
             // If new request is supposed to be earlier than the current entry's scheduled
             // time (for eg: the new request is user triggered and the current entry is the
             // reconciler's usual retry), then give priority to the new request.
             Entry::Occupied(mut old_entry) if old_entry.get().run_at >= request.run_at => {
                 // Old entry will run after the new request, so replace it..
                 let entry = old_entry.get_mut();
-                self.queue
-                    .reset_at(&entry.queue_key, request.run_at + *self.debounce);
-                entry.run_at = request.run_at + *self.debounce;
+                self.queue.reset_at(&entry.queue_key, next_time);
+                entry.run_at = next_time;
                 old_entry.replace_key();
             }
             Entry::Occupied(_old_entry) => {
@@ -93,8 +96,8 @@
                 // No old entry, we're free to go!
                 let message = entry.key().clone();
                 entry.insert(ScheduledEntry {
-                    run_at: request.run_at + *self.debounce,
-                    queue_key: self.queue.insert_at(message, request.run_at + *self.debounce),
+                    run_at: next_time,
+                    queue_key: self.queue.insert_at(message, next_time),
                 });
             }
         }
@@ -280,6 +283,13 @@
     Scheduler::new(requests, debounce)
 }
 
+// internal fallback for overflows in schedule times
+pub(crate) fn far_future() -> Instant {
+    // private method from tokio for convenience - remove if upstream becomes pub
+    // https://github.com/tokio-rs/tokio/blob/6fcd9c02176bf3cd570bc7de88edaa3b95ea480a/tokio/src/time/instant.rs#L57-L63
+    Instant::now() + Duration::from_secs(86400 * 365 * 30)
+}
+
 #[cfg(test)]
 mod tests {
     use crate::utils::KubeRuntimeStreamExt;