From 0a5c4295e008b3687d160957328a934c85489f9b Mon Sep 17 00:00:00 2001
From: Jef Roosens <roosensjef@gmail.com>
Date: Mon, 12 Dec 2022 20:59:43 +0100
Subject: [PATCH] feat(server): properly reschedule jobs after polling

---
 src/build/queue.v       | 50 ++++++++++++++++++++++++++++++++++-------
 src/server/api_builds.v |  6 ++---
 2 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/src/build/queue.v b/src/build/queue.v
index 65b279e2..b704926f 100644
--- a/src/build/queue.v
+++ b/src/build/queue.v
@@ -8,12 +8,16 @@ import util
 
 struct BuildJob {
 pub:
-	// Earliest point this
+	// Next timestamp from which point this job is allowed to be executed
 	timestamp time.Time
-	config    BuildConfig
+	// Required for calculating next timestamp after having pop'ed a job
+	ce CronExpression
+	// Actual build config sent to the agent
+	config BuildConfig
 }
 
-// Overloaded operator for comparing ScheduledBuild objects
+// Allows BuildJob structs to be sorted according to their timestamp in
+// MinHeaps
 fn (r1 BuildJob) < (r2 BuildJob) bool {
 	return r1.timestamp < r2.timestamp
 }
@@ -39,7 +43,9 @@ pub fn new_job_queue(default_schedule CronExpression, default_base_image string)
 	}
 }
 
-// insert a new job into the queue for a given target on an architecture.
+// insert a new target's job into the queue for the given architecture. This
+// job will then be endlessly rescheduled after being pop'ed, unless removed
+// explicitely.
 pub fn (mut q BuildJobQueue) insert(target Target, arch string) ! {
 	lock q.mutex {
 		if arch !in q.queues {
@@ -58,6 +64,7 @@ pub fn (mut q BuildJobQueue) insert(target Target, arch string) ! {
 
 		job := BuildJob{
 			timestamp: timestamp
+			ce: ce
 			config: BuildConfig{
 				target_id: target.id
 				kind: target.kind
@@ -69,10 +76,25 @@ pub fn (mut q BuildJobQueue) insert(target Target, arch string) ! {
 			}
 		}
 
+		dump(job)
 		q.queues[arch].insert(job)
 	}
 }
 
+// reschedule the given job by calculating the next timestamp and re-adding it
+// to its respective queue. This function is called by the pop functions
+// *after* having pop'ed the job.
+fn (mut q BuildJobQueue) reschedule(job BuildJob, arch string) ! {
+	new_timestamp := job.ce.next_from_now()!
+
+	new_job := BuildJob{
+		...job
+		timestamp: new_timestamp
+	}
+
+	q.queues[arch].insert(new_job)
+}
+
 // peek shows the first job for the given architecture that's ready to be
 // executed, if present.
 pub fn (q &BuildJobQueue) peek(arch string) ?BuildJob {
@@ -99,10 +121,17 @@ pub fn (mut q BuildJobQueue) pop(arch string) ?BuildJob {
 			return none
 		}
 
-		job := q.queues[arch].peek() or { return none }
+		mut job := q.queues[arch].peek() or { return none }
 
 		if job.timestamp < time.now() {
-			return q.queues[arch].pop()
+			job = q.queues[arch].pop()?
+
+			// TODO how do we handle this properly? Is it even possible for a
+			// cron expression to not return a next time if it's already been
+			// used before?
+			q.reschedule(job, arch) or {}
+
+			return job
 		}
 	}
 
@@ -119,10 +148,15 @@ pub fn (mut q BuildJobQueue) pop_n(arch string, n int) []BuildJob {
 		mut out := []BuildJob{}
 
 		for out.len < n {
-			job := q.queues[arch].peek() or { break }
+			mut job := q.queues[arch].peek() or { break }
 
 			if job.timestamp < time.now() {
-				out << q.queues[arch].pop() or { break }
+				job = q.queues[arch].pop() or { break }
+
+				// TODO idem
+				q.reschedule(job, arch) or {}
+
+				out << job
 			} else {
 				break
 			}
diff --git a/src/server/api_builds.v b/src/server/api_builds.v
index 62948cd3..ec3c8ec2 100644
--- a/src/server/api_builds.v
+++ b/src/server/api_builds.v
@@ -6,8 +6,8 @@ import web.response { new_data_response, new_response }
 // import util
 // import models { BuildLog, BuildLogFilter }
 
-['/api/v1/builds/poll'; auth; get]
-fn (mut app App) v1_poll_build_queue() web.Result {
+['/api/v1/jobs/poll'; auth; get]
+fn (mut app App) v1_poll_job_queue() web.Result {
 	arch := app.query['arch'] or {
 		return app.json(.bad_request, new_response('Missing arch query arg.'))
 	}
@@ -17,7 +17,7 @@ fn (mut app App) v1_poll_build_queue() web.Result {
 	}
 	max := max_str.int()
 
-	mut out := app.job_queue.pop_n(arch, max)
+	mut out := app.job_queue.pop_n(arch, max).map(it.config)
 
 	return app.json(.ok, new_data_response(out))
 }