Refactoring Prometheus package (#218)

* Remove outdated instructions

* Refactor NewServer functionality to include unit tests

* Add unit tests for prometheus' getRouter function

Author: ncaak

Diff for: docs/new-releases.md

@@ -19,15 +19,7 @@
 3. Publish new DVO release to Operator-Hub
 
     - OperatorHub Repository for DVO - [DVO OLM](https://github.com/k8s-operatorhub/community-operators/tree/main/operators/deployment-validation-operator)
-    - Edit deployment-validation-operator.package.yaml to reflect the new release
-    
-    ```yaml
-    # RELEASE VERSION == 0.2.0, 0.2.1, etc.
-    
-    * channels.currentCSV: deployment-validation-operator.v<RELEASE VERSION>
-    ```
-    
-    - As a shortcut, you may choose to copy+paste the most recent already-existing DVO version directory (ex. 0.2.0, 0.2.1) and change the name of the directory to reflect the new release version
+    - Copy and Paste the pre-existing DVO version directory (ex. 0.2.0, 0.2.1) and change the name of the directory to reflect the new release version
     - Modify the clusterserviceversion file's name within the directory to reflect the new release version
 
     ```yaml
@@ -39,6 +31,7 @@
     * spec.install.spec.deployments.spec.template.spec.containers.image: quay.io/deployment-validation-operator/dv-operator:<RELEASE VERSION>
     * spec.links.url: https://quay.io/deployment-validation-operator/dv-operator:<RELEASE VERSION>
     * spec.version: <RELEASE VERSION>
+    * spec.skipRange: '>=0.0.10 <X.Y.Z' X.Y.Z being the new RELEASE VERSION
 
     # Modify the following line to reflect the previous release version for upgrade purposes 
     # (ex. If going from 0.2.1 -> 0.2.2, then the previous release was 0.2.1)

Diff for: pkg/prometheus/prometheus.go

@@ -18,34 +18,66 @@ type Registry interface {
 	Gather() ([]*dto.MetricFamily, error)
 }
 
+// registerCollectorError is returned by the NewServer method if the Registry
+// causes any error on registering a Collector
+type registerCollectorError struct {
+	collector string
+	trace     error
+}
+
+func (err registerCollectorError) Error() string {
+	return fmt.Sprintf("registering %s collector: %s", err.collector, err.trace.Error())
+}
+
+// NewServer returns a server configured to work on path and address given
+// It registers a collector which exports the current state of process metrics
+// and a collector that exports metrics about the current process
+// It may return registerCollectorError if the collectors are already registered
 func NewServer(registry Registry, path, addr string) (*Server, error) {
 	if !strings.HasPrefix(path, "/") {
 		path = "/" + path
 	}
 
+	mux, err := getRouter(registry, path)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Server{
+		s: &http.Server{
+			Addr:              addr,
+			Handler:           mux,
+			ReadHeaderTimeout: 2 * time.Second,
+		},
+	}, nil
+}
+
+// getRouter registers two collectors to deliver metrics on a given path
+// It may return registerCollectorError if the collectors are already registered
+func getRouter(registry Registry, path string) (*http.ServeMux, error) {
 	var (
 		processCollector = collectors.NewProcessCollector(collectors.ProcessCollectorOpts{})
 		goCollector      = collectors.NewGoCollector()
 	)
 
 	if err := registry.Register(processCollector); err != nil {
-		return nil, fmt.Errorf("registering process collector: %w", err)
+		return nil, registerCollectorError{
+			collector: "process",
+			trace:     err,
+		}
 	}
 
 	if err := registry.Register(goCollector); err != nil {
-		return nil, fmt.Errorf("registering go collector: %w", err)
+		return nil, registerCollectorError{
+			collector: "go",
+			trace:     err,
+		}
 	}
 
 	mux := http.NewServeMux()
 	mux.Handle(path, promhttp.HandlerFor(registry, promhttp.HandlerOpts{}))
 
-	return &Server{
-		s: &http.Server{
-			Addr:              addr,
-			Handler:           mux,
-			ReadHeaderTimeout: 2 * time.Second,
-		},
-	}, nil
+	return mux, nil
 }
 
 type Server struct {

Diff for: pkg/prometheus/prometheus_test.go

@@ -0,0 +1,49 @@
+package prometheus
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
+	"github.com/stretchr/testify/assert"
+)
+
+// TestOptionsStruct runs four tests on options struct methods:
+// -
+func TestGetRouter(t *testing.T) {
+
+	t.Run("router path is available", func(t *testing.T) {
+		// Given
+		recorder := httptest.NewRecorder()
+		mockPath := "/test"
+		mockReq, _ := http.NewRequest("GET", mockPath, nil)
+		mockRegistry := prometheus.NewRegistry()
+
+		// When
+		mux, err := getRouter(mockRegistry, mockPath)
+		mux.ServeHTTP(recorder, mockReq)
+
+		// Assert
+		assert.NoError(t, err)
+		assert.Equal(t, http.StatusOK, recorder.Code)
+	})
+
+	t.Run("handle error on collector registry", func(t *testing.T) {
+		// Given
+		mockRegistry := prometheus.NewRegistry()
+		mockCollector := collectors.NewGoCollector()
+		errMock := mockRegistry.Register(mockCollector)
+		if errMock != nil {
+			t.Errorf("Unexpected error at registering mock : %s", errMock.Error())
+		}
+
+		// When
+		_, err := getRouter(mockRegistry, "/test")
+
+		// Assert
+		assert.Error(t, err)
+		assert.IsType(t, registerCollectorError{}, err)
+	})
+}