WIP: metric guide for ks

sig-observability/concepts-and-designs/how-to-add-new-metric-to-kubesphere.md

@@ -0,0 +1,61 @@
+# Why we need to add metrics to kubesphere
+
+Metrics can provide insight into the behavior and health of our system. They represent the raw material used by monitoring system to build a holistic view of kubesphere, automate responses to changes, and alert human beings when required.
+
+# How to add new metric
+
+* 1. [Define the metric](#Define)
+* 2. [Register the metric](#Register)
+* 3. [Export the metric](#Export)
+
+
+## 1. <a name='Define'></a>Define the metric
+Define the metric in the  file `metric.go` of you package or somewhere else. 
+
+ ```go
+ package application
+
+import (
+	compbasemetrics "k8s.io/component-base/metrics"
+	"kubesphere.io/kubesphere/pkg/utils/metrics"
+ )
+
+var (
+    // add a counter metric
+	appTemplateCreationCounter = compbasemetrics.NewCounterVec(
+		&compbasemetrics.CounterOpts{
+			Name:           "application_template_creation",  // metric name
+			Help:           "Counter of application template creation broken out for each workspace, name and create state",    // metric help info
+			StabilityLevel: compbasemetrics.ALPHA,  //represents the API guarantees for a given defined metric
+		},
+        //we want to export the namespace, name  and current state of the appTemplate
+        []string{"workspace", "name", "state"},  // the  labels of the metric
+	)
+ )
+
+```
+
+## 2. <a name='Register'></a>Register the metric
+```go
+ package application
+ import (
+    "kubesphere.io/kubesphere/pkg/utils/metrics"
+ )
+
+ func init(){
+    Register()
+ }
+
+ func Register() {
+    metrics.MustRegister(appTemplateCreationCounter)
+ }
+```
+
+## 3. <a name='Export'></a>Export the metric
+```go
+package application
+func (c *appTemplateOperator) CreateApp(request *CreateAppRequest) {
+      // export app template create metric with label values
+     appTemplateCreationCounter.WithLabelValues("workspace", "Name", "failed").Inc()
+}
+```