WIP: generic activation through + new interval-based replication trigger

daemon/job/trigger/trigger.go

@@ -0,0 +1,103 @@
+package trigger
+
+import (
+	"context"
+
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/daemon/logging/trace"
+)
+
+type Triggers struct {
+	spawned  bool
+	triggers []*Trigger
+}
+
+type Trigger struct {
+	id     string
+	signal chan struct{}
+}
+
+func FromConfig([]*config.ReplicationTriggerEnum) (*Triggers, error) {
+	panic("unimpl")
+	return &Triggers{
+		spawned: false,
+	}, nil
+}
+
+func Empty() *Triggers {
+	panic("unimpl")
+}
+
+func New(id string) *Trigger {
+	return &Trigger{
+		id:     id,
+		signal: make(chan struct{}),
+	}
+}
+
+func (t *Trigger) ID() string {
+	return t.id
+}
+
+func (t *Trigger) Fire() error {
+	panic("unimpl")
+}
+
+func (t *Triggers) Spawn(ctx context.Context, additionalTriggers []*Trigger) (chan *Trigger, trace.DoneFunc) {
+	if t.spawned {
+		panic("must only spawn once")
+	}
+	t.spawned = true
+	t.triggers = append(t.triggers, additionalTriggers...)
+	childCtx, endTask := trace.WithTask(ctx, "triggers")
+	sink := make(chan *Trigger)
+	go t.task(childCtx, sink)
+	return sink, endTask
+}
+
+type triggering struct {
+	trigger *Trigger
+	handled chan struct{}
+}
+
+func (t *Triggers) task(ctx context.Context, sink chan *Trigger) {
+	triggered := make(chan triggering, len(t.triggers))
+	for _, t := range t.triggers {
+		t := t
+		go func() {
+			for {
+				select {
+				case <-ctx.Done():
+					return
+				case <-t.signal:
+					handled := make(chan struct{})
+					select {
+					case triggered <- triggering{trigger: t, handled: handled}:
+					default:
+						panic("this funtion ensures that there's always room in the channel")
+					}
+					select {
+					case <-handled:
+					case <-ctx.Done():
+						return
+					}
+				}
+			}
+		}()
+	}
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case triggering := <-triggered:
+			select {
+			case sink <- triggering.trigger:
+			default:
+				getLogger(ctx).
+					WithField("trigger_id", triggering.trigger.id).
+					Warn("dropping triggering because job is busy")
+			}
+			close(triggering.handled)
+		}
+	}
+}