agent: Adding minimum check interval. Fixes #64.

command/agent/agent.go

@@ -417,6 +417,11 @@ func (a *Agent) AddCheck(check *structs.HealthCheck, chkType *CheckType) error {
 			if _, ok := a.checkMonitors[check.CheckID]; ok {
 				return fmt.Errorf("CheckID is already registered")
 			}
+			if chkType.Interval < MinInterval {
+				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has interval below minimum of %v",
+					check.CheckID, MinInterval))
+				chkType.Interval = MinInterval
+			}
 
 			monitor := &CheckMonitor{
 				Notify:   &a.state,

command/agent/agent_test.go

@@ -205,6 +205,39 @@ func TestAgent_AddCheck(t *testing.T) {
 	}
 }
 
+func TestAgent_AddCheck_MinInterval(t *testing.T) {
+	dir, agent := makeAgent(t, nextConfig())
+	defer os.RemoveAll(dir)
+	defer agent.Shutdown()
+
+	health := &structs.HealthCheck{
+		Node:    "foo",
+		CheckID: "mem",
+		Name:    "memory util",
+		Status:  structs.HealthUnknown,
+	}
+	chk := &CheckType{
+		Script:   "exit 0",
+		Interval: time.Microsecond,
+	}
+	err := agent.AddCheck(health, chk)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// Ensure we have a check mapping
+	if _, ok := agent.state.Checks()["mem"]; !ok {
+		t.Fatalf("missing mem check")
+	}
+
+	// Ensure a TTL is setup
+	if mon, ok := agent.checkMonitors["mem"]; !ok {
+		t.Fatalf("missing mem monitor")
+	} else if mon.Interval != MinInterval {
+		t.Fatalf("bad mem monitor interval")
+	}
+}
+
 func TestAgent_RemoveCheck(t *testing.T) {
 	dir, agent := makeAgent(t, nextConfig())
 	defer os.RemoveAll(dir)

command/agent/check.go

@@ -12,6 +12,12 @@ import (
 	"time"
 )
 
+const (
+	// Do not allow for a interval below this value.
+	// Otherwise we risk fork bombing a system.
+	MinInterval = time.Second
+)
+
 // CheckType is used to create either the CheckMonitor
 // or the CheckTTL. Only one of TTL or Script/Interval
 // needs to be provided