From 3d826d96cf03f0a82c5fead55860f7e480d46649 Mon Sep 17 00:00:00 2001
From: Brett Buddin <brett@buddin.org>
Date: Thu, 26 Mar 2020 13:37:25 -0400
Subject: [PATCH 1/2] feat(influxd): flag to disable scheduling of tasks

---
 cmd/influxd/launcher/launcher.go         | 51 +++++++++++++++++-------
 task/backend/scheduler/noop_scheduler.go | 18 +++++++++
 2 files changed, 54 insertions(+), 15 deletions(-)
 create mode 100644 task/backend/scheduler/noop_scheduler.go

diff --git a/cmd/influxd/launcher/launcher.go b/cmd/influxd/launcher/launcher.go
index a446d7dd8ad..45c26e81f83 100644
--- a/cmd/influxd/launcher/launcher.go
+++ b/cmd/influxd/launcher/launcher.go
@@ -273,6 +273,12 @@ func buildLauncherCommand(l *Launcher, cmd *cobra.Command) {
 			Default: true,
 			Desc:    "toggles read-only mode for the new meta store, if so, the reads are duplicated between the old and new store (has meaning only if the new meta store is enabled)",
 		},
+		{
+			DestP:   &l.noTasks,
+			Flag:    "no-tasks",
+			Default: false,
+			Desc:    "disables the task scheduler",
+		},
 	}
 
 	cli.BindOptions(cmd, opts)
@@ -319,7 +325,8 @@ type Launcher struct {
 	natsServer *nats.Server
 	natsPort   int
 
-	scheduler          *scheduler.TreeScheduler
+	noTasks            bool
+	scheduler          stoppingScheduler
 	executor           *executor.Executor
 	taskControlService taskbackend.TaskControlService
 
@@ -333,6 +340,11 @@ type Launcher struct {
 	apibackend *http.APIBackend
 }
 
+type stoppingScheduler interface {
+	scheduler.Scheduler
+	Stop()
+}
+
 // NewLauncher returns a new instance of Launcher connected to standard in/out/err.
 func NewLauncher() *Launcher {
 	return &Launcher{
@@ -682,22 +694,31 @@ func (m *Launcher) run(ctx context.Context) (err error) {
 		m.reg.MustRegister(executorMetrics.PrometheusCollectors()...)
 		schLogger := m.log.With(zap.String("service", "task-scheduler"))
 
-		sch, sm, err := scheduler.NewScheduler(
-			executor,
-			taskbackend.NewSchedulableTaskService(m.kvService),
-			scheduler.WithOnErrorFn(func(ctx context.Context, taskID scheduler.ID, scheduledAt time.Time, err error) {
-				schLogger.Info(
-					"error in scheduler run",
-					zap.String("taskID", platform.ID(taskID).String()),
-					zap.Time("scheduledAt", scheduledAt),
-					zap.Error(err))
-			}),
-		)
-		if err != nil {
-			m.log.Fatal("could not start task scheduler", zap.Error(err))
+		var sch stoppingScheduler = &scheduler.NoopScheduler{}
+		if !m.noTasks {
+			var (
+				sm  *scheduler.SchedulerMetrics
+				err error
+			)
+			sch, sm, err = scheduler.NewScheduler(
+				executor,
+				taskbackend.NewSchedulableTaskService(m.kvService),
+				scheduler.WithOnErrorFn(func(ctx context.Context, taskID scheduler.ID, scheduledAt time.Time, err error) {
+					schLogger.Info(
+						"error in scheduler run",
+						zap.String("taskID", platform.ID(taskID).String()),
+						zap.Time("scheduledAt", scheduledAt),
+						zap.Error(err))
+				}),
+			)
+			if err != nil {
+				m.log.Fatal("could not start task scheduler", zap.Error(err))
+			}
+			m.reg.MustRegister(sm.PrometheusCollectors()...)
 		}
+
 		m.scheduler = sch
-		m.reg.MustRegister(sm.PrometheusCollectors()...)
+
 		coordLogger := m.log.With(zap.String("service", "task-coordinator"))
 		taskCoord := coordinator.NewCoordinator(
 			coordLogger,
diff --git a/task/backend/scheduler/noop_scheduler.go b/task/backend/scheduler/noop_scheduler.go
new file mode 100644
index 00000000000..b83b1bb2f5d
--- /dev/null
+++ b/task/backend/scheduler/noop_scheduler.go
@@ -0,0 +1,18 @@
+package scheduler
+
+// NoopScheduler is a no-op scheduler. It is used when we don't want the
+// standard scheduler to run (e.g. when "--no-tasks" flag is present).
+type NoopScheduler struct{}
+
+// Schedule is a mocked Scheduler.Schedule method.
+func (n *NoopScheduler) Schedule(task Schedulable) error {
+	return nil
+}
+
+// Release is a mocked Scheduler.Release method.
+func (n *NoopScheduler) Release(taskID ID) error {
+	return nil
+}
+
+// Stop is a mocked stop method.
+func (n *NoopScheduler) Stop() {}

From 19abbebef68a258f6ce9c9bbc00a28760039c6b6 Mon Sep 17 00:00:00 2001
From: Brett Buddin <brett@buddin.org>
Date: Fri, 27 Mar 2020 12:41:25 -0400
Subject: [PATCH 2/2] chore(influxd): update changelog for no-tasks flag.

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5681c708e5f..486d9be48a7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 1. [17400](https://github.com/influxdata/influxdb/pull/17400): Be able to delete bucket by name via cli
 1. [17396](https://github.com/influxdata/influxdb/pull/17396): Add module to write line data to specified url, org, and bucket
 1. [17448](https://github.com/influxdata/influxdb/pull/17448): Add foundation for pkger stacks, stateful package management
+1. [17462](https://github.com/influxdata/influxdb/pull/17462): Flag to disable scheduling of tasks
 
 ### Bug Fixes