Node Level Critical Events filter

This Commit
- adds `NodeEventsChecker` filter to send notifs on node level critical events like `NodeNotReady` and `NodeReady`

pkg/controller/controller.go

@@ -77,6 +77,25 @@ func RegisterInformers(c *config.Config) {
 				sendEvent(obj, nil, c, kind, config.ErrorEvent)
 			}
 		},
+		UpdateFunc: func(old, new interface{}) {
+			_, err := cache.MetaNamespaceKeyFunc(new)
+			if err != nil {
+				log.Logger.Errorf("Failed to get MetaNamespaceKey from event resource")
+				return
+			}
+			eventObj, ok := new.(*apiV1.Event)
+			if !ok {
+				return
+			}
+
+			// Kind of involved object
+			kind := strings.ToLower(eventObj.InvolvedObject.Kind)
+
+			// Send events update notifs if InvolvedObject is node
+			if kind == "node" {
+				sendEvent(new, old, c, kind, config.ErrorEvent)
+			}
+		},
 	})
 
 	stopCh := make(chan struct{})

pkg/filterengine/filters/node_event_checker.go

@@ -0,0 +1,65 @@
+// NodeEventsChecker filter to send notifications on critical node events
+
+package filters
+
+import (
+	"fmt"
+
+	"github.com/infracloudio/botkube/pkg/events"
+	"github.com/infracloudio/botkube/pkg/filterengine"
+	apiV1 "k8s.io/api/core/v1"
+
+	log "github.com/infracloudio/botkube/pkg/logging"
+)
+
+const (
+	// NodeNotReady reason indicates Node is NotReady state
+	NodeNotReady string = "NodeNotReady"
+	// NodeReady reason indicates Node is Ready state
+	NodeReady string = "NodeReady"
+)
+
+// NodeEventsChecker checks job status and adds message in the events structure
+type NodeEventsChecker struct {
+	Description string
+}
+
+// Register filter
+func init() {
+	filterengine.DefaultFilterEngine.Register(NodeEventsChecker{
+		Description: "Sends notifications on node level critical events.",
+	})
+}
+
+// Run filers and modifies event struct
+func (f NodeEventsChecker) Run(object interface{}, event *events.Event) {
+
+	// Run filter only on Node events
+	if event.Kind != "Node" {
+		return
+	}
+
+	eventObj, ok := object.(*apiV1.Event)
+	if !ok {
+		return
+	}
+
+	// update event details
+	switch event.Reason {
+	case NodeNotReady:
+		event.Level = events.Critical
+	case NodeReady:
+		event.Level = events.Info
+		event.Messages = []string{fmt.Sprintf("%s\n", eventObj.Message)}
+	default:
+		// skip events with least significant reasons
+		event.Skip = true
+	}
+
+	log.Logger.Debug("Node Critical Event filter successful!")
+}
+
+// Describe filter
+func (f NodeEventsChecker) Describe() string {
+	return f.Description
+}