nomad: adding skeleton no-op plan evaluator

nomad/leader.go

@@ -100,7 +100,8 @@ func (s *Server) establishLeadership() error {
 	// Enable the plan queue, since we are now the leader
 	s.planQueue.SetEnabled(true)
 
-	// TODO: Start the plan evaluator
+	// Start the plan evaluator
+	go s.planApply()
 
 	// Enable the eval broker, since we are now the leader
 	s.evalBroker.SetEnabled(true)

nomad/plan_apply.go

@@ -0,0 +1,28 @@
+package nomad
+
+import "github.com/hashicorp/nomad/nomad/structs"
+
+// planApply is a long lived goroutine that reads plan allocations from
+// the plan queue, determines if they can be applied safely and applies
+// them via Raft.
+func (s *Server) planApply() {
+	for {
+		// Pull the next pending plan, exit if we are no longer leader
+		pending, err := s.planQueue.Dequeue(0)
+		if err != nil {
+			return
+		}
+
+		// TODO: Evaluate the plan
+
+		// TODO: Apply the plan
+
+		// TODO: Prepare the response
+		result := &structs.PlanResult{
+			AllocIndex: 1000,
+		}
+
+		// Respond to the plan
+		pending.respond(result, nil)
+	}
+}