feat(cron): improve sleep calculation; prevent invalid rescheduling of

finished builds

src/cron/daemon/build.v

@@ -2,6 +2,7 @@ module daemon
 
 import time
 import sync.stdatomic
+import rand
 
 const build_empty = 0
 
@@ -9,21 +10,23 @@ const build_running = 1
 
 const build_done = 2
 
-// reschedule_builds looks for any builds with status code 2 & re-adds them to
-// the queue.
-fn (mut d Daemon) reschedule_builds() ? {
+// clean_finished_builds removes finished builds from the build slots & returns
+// them.
+fn (mut d Daemon) clean_finished_builds() ?[]ScheduledBuild {
+	mut out := []ScheduledBuild{}
+
 	for i in 0 .. d.atomics.len {
 		if stdatomic.load_u64(&d.atomics[i]) == daemon.build_done {
 			stdatomic.store_u64(&d.atomics[i], daemon.build_empty)
-			sb := d.builds[i]
-
-			d.schedule_build(sb.repo_id, sb.repo) ?
+			out << d.builds[i]
 		}
 	}
+
+	return out
 }
 
 // update_builds starts as many builds as possible.
-fn (mut d Daemon) update_builds() ? {
+fn (mut d Daemon) start_new_builds() ? {
 	now := time.now()
 
 	for d.queue.len() > 0 {
@@ -31,8 +34,8 @@ fn (mut d Daemon) update_builds() ? {
 			sb := d.queue.pop() ?
 
 			// If this build couldn't be scheduled, no more will be possible.
-			// TODO a build that couldn't be scheduled should be re-added to the queue.
 			if !d.start_build(sb) {
+				d.queue.insert(sb)
 				break
 			}
 		} else {
@@ -60,7 +63,20 @@ fn (mut d Daemon) start_build(sb ScheduledBuild) bool {
 // run_build actually starts the build process for a given repo.
 fn (mut d Daemon) run_build(build_index int, sb ScheduledBuild) ? {
 	d.linfo('build $sb.repo.url')
-	time.sleep(10 * time.second)
+	time.sleep(rand.int_in_range(1, 6) ? * time.second)
 
 	stdatomic.store_u64(&d.atomics[build_index], daemon.build_done)
 }
+
+// current_build_count returns how many builds are currently running.
+fn (mut d Daemon) current_build_count() int {
+	mut res := 0
+
+	for i in 0 .. d.atomics.len {
+		if stdatomic.load_u64(&d.atomics[i]) == daemon.build_running {
+			res += 1
+		}
+	}
+
+	return res
+}

src/cron/daemon/daemon.v

@@ -6,7 +6,6 @@ import log
 import datatypes { MinHeap }
 import cron.expression { CronExpression, parse_expression }
 import math
-import arrays
 
 struct ScheduledBuild {
 pub:
@@ -64,40 +63,51 @@ pub fn init_daemon(logger log.Log, address string, api_key string, base_image st
 // periodically refreshes the list of repositories to ensure we stay in sync.
 pub fn (mut d Daemon) run() ? {
 	for {
+		finished_builds := d.clean_finished_builds() ?
+
 		// Update the API's contents if needed & renew the queue
 		if time.now() >= d.api_update_timestamp {
 			d.renew_repos() ?
 			d.renew_queue() ?
 		}
-
-		// Cleans up finished builds, opening up spots for new builds
-		d.reschedule_builds() ?
+		// The finished builds should only be rescheduled if the API contents
+		// haven't been renewed.
+		else {
+			for sb in finished_builds {
+				d.schedule_build(sb.repo_id, sb.repo) ?
+			}
+		}
 
 		// TODO rebuild builder image when needed
 
 		// Schedules new builds when possible
-		d.update_builds() ?
+		d.start_new_builds() ?
+
+		// If there are builds currently running, the daemon should refresh
+		// every second to clean up any finished builds & start new ones.
+		mut delay := time.Duration(1 * time.second)
 
 		// Sleep either until we have to refresh the repos or when the next
 		// build has to start, with a minimum of 1 second.
-		now := time.now()
+		if d.current_build_count() == 0 {
+			now := time.now()
+			delay = d.api_update_timestamp - now
 
-		mut delay := d.api_update_timestamp - now
+			if d.queue.len() > 0 {
+				time_until_next_job := d.queue.peek() ?.timestamp - now
 
-		if d.queue.len() > 0 {
-			time_until_next_job := d.queue.peek() ?.timestamp - now
-
-			delay = math.min(delay, time_until_next_job)
+				delay = math.min(delay, time_until_next_job)
+			}
 		}
 
-		d.ldebug('Sleeping for ${delay}...')
-
-		// TODO if there are builds active, the sleep time should be much lower to clean up the builds when they're finished.
-
 		// We sleep for at least one second. This is to prevent the program
 		// from looping agressively when a cronjob can be scheduled, but
 		// there's no spots free for it to be started.
-		time.sleep(math.max(delay, 1 * time.second))
+		delay = math.max(delay, 1 * time.second)
+
+		d.ldebug('Sleeping for ${delay}...')
+
+		time.sleep(delay)
 	}
 }
 

src/cron/expression/expression.v

@@ -114,6 +114,8 @@ pub fn (ce &CronExpression) next(ref time.Time) ?time.Time {
 	})
 }
 
+// next_from_now returns the result of ce.next(ref) where ref is the result of
+// time.now().
 pub fn (ce &CronExpression) next_from_now() ?time.Time {
 	return ce.next(time.now())
 }

vieter.toml

@@ -10,4 +10,5 @@ default_arch = "x86_64"
 address = "http://localhost:8000"
 
 global_schedule = '* *'
-
+api_update_frequency = 2
+max_concurrent_builds = 3