feat(operator): add support for configuration file

operator/Dockerfile

@@ -11,7 +11,7 @@ COPY . .
 RUN go mod download
 
 # Build
-RUN CGO_ENABLED=0 GOOS=linux GO111MODULE=on go build -a -o manager main.go
+RUN CGO_ENABLED=0 GOOS=linux GO111MODULE=on go build -a -o manager main.go config.go
 
 # Use distroless as minimal base image to package the manager binary
 # Refer to https://github.com/GoogleContainerTools/distroless for more details

operator/Makefile

@@ -46,11 +46,11 @@ clean:
 
 # Build manager binary
 manager: generate fmt vet
-	go build -o bin/manager main.go
+	go build -o bin/manager main.go ./config.go
 
 # Run against the configured Kubernetes cluster in ~/.kube/config
 run: generate fmt vet manifests
-	go run ./main.go
+	go run ./main.go ./config.go
 
 # Install CRDs into a cluster
 install: manifests kustomize

operator/config.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"os"
+
+	"gopkg.in/yaml.v3"
+)
+
+type Config struct {
+	Sidecar SidecarConfig `yaml:"sidecar,omitempty"`
+}
+
+type SidecarConfig struct {
+	Image string `yaml:"image,omitempty"`
+}
+
+func ReadConfig(configPath string) (Config, error) {
+	// Set default values
+	config := Config{
+		Sidecar: SidecarConfig{
+			Image: "sumologic/tailing-sidecar:latest",
+		},
+	}
+
+	content, err := os.ReadFile(configPath)
+	if err != nil {
+		return config, err
+	}
+	err = yaml.Unmarshal(content, &config)
+	if err != nil {
+		return config, err
+	}
+	return config, err
+}
+
+func (c *Config) Validate() error {
+	return nil
+}

operator/config_test.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestReadConfig(t *testing.T) {
+	testCases := []struct {
+		name          string
+		content       string
+		expected      Config
+		expectedError error
+	}{
+		{
+			name:    "empty file",
+			content: ``,
+			expected: Config{
+				Sidecar: SidecarConfig{
+					Image: "sumologic/tailing-sidecar:latest",
+				},
+			},
+			expectedError: nil,
+		},
+		{
+			name: "defaults",
+			content: `
+sidecar:
+  commands:
+    - test
+    - command`,
+			expected: Config{
+				Sidecar: SidecarConfig{
+					Image: "sumologic/tailing-sidecar:latest",
+				},
+			},
+			expectedError: nil,
+		},
+		{
+			name: "overwrite defaults",
+			content: `
+sidecar:
+  image: my-new-image`,
+			expected: Config{
+				Sidecar: SidecarConfig{
+					Image: "my-new-image",
+				},
+			},
+			expectedError: nil,
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			file, err := ioutil.TempFile(".", "prefix")
+			require.NoError(t, err)
+			defer os.Remove(file.Name())
+
+			_, err = file.WriteString(tt.content)
+			require.NoError(t, err)
+			config, err := ReadConfig(file.Name())
+
+			if tt.expectedError != nil {
+				require.Error(t, tt.expectedError, err)
+				return
+			}
+
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, config)
+		})
+	}
+}
+
+func TestReadConfigInvalidFile(t *testing.T) {
+	_, err := ReadConfig("non-existing-file")
+	require.Error(t, err)
+	require.EqualError(t, err, "open non-existing-file: no such file or directory")
+}

operator/go.mod

@@ -7,13 +7,17 @@ require (
 	github.com/nsf/jsondiff v0.0.0-20200515183724-f29ed568f4ce
 	github.com/onsi/ginkgo v1.16.5
 	github.com/onsi/gomega v1.27.6
+	github.com/stretchr/testify v1.8.1
 	gomodules.xyz/jsonpatch/v2 v2.2.0
+	gopkg.in/yaml.v3 v3.0.1
 	k8s.io/api v0.26.3
 	k8s.io/apimachinery v0.27.1
 	k8s.io/client-go v0.26.3
 	sigs.k8s.io/controller-runtime v0.14.6
 )
 
+require github.com/pmezard/go-difflib v1.0.0 // indirect
+
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
@@ -63,7 +67,6 @@ require (
 	gopkg.in/inf.v0 v0.9.1 // indirect
 	gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
-	gopkg.in/yaml.v3 v3.0.1 // indirect
 	k8s.io/apiextensions-apiserver v0.26.1 // indirect
 	k8s.io/component-base v0.26.1 // indirect
 	k8s.io/klog/v2 v2.90.1 // indirect

operator/main.go

@@ -50,15 +50,40 @@ func main() {
 	var metricsAddr string
 	var enableLeaderElection bool
 	var tailingSidecarImage string
+	var configPath string
+	var config Config
+	var err error
+
 	flag.StringVar(&metricsAddr, "metrics-addr", ":8080", "The address the metric endpoint binds to.")
 	flag.BoolVar(&enableLeaderElection, "enable-leader-election", false,
 		"Enable leader election for controller manager. "+
 			"Enabling this will ensure there is only one active controller manager.")
-	flag.StringVar(&tailingSidecarImage, "tailing-sidecar-image", "sumologic/tailing-sidecar:latest", "tailing sidecar image")
+	flag.StringVar(&tailingSidecarImage, "tailing-sidecar-image", "", "tailing sidecar image")
+	flag.StringVar(&configPath, "config", "", "Path to the configuration file")
 	flag.Parse()
 
 	ctrl.SetLogger(zap.New(zap.UseDevMode(true)))
 
+	if configPath != "" {
+		config, err = ReadConfig(configPath)
+
+		if err != nil {
+			setupLog.Error(err, "unable to read configuration", "configPath", configPath)
+			os.Exit(1)
+		}
+	} else {
+		config = Config{}
+	}
+
+	if err := config.Validate(); err != nil {
+		setupLog.Error(err, "configuration error", "configPath", configPath)
+		os.Exit(1)
+	}
+
+	if tailingSidecarImage != "" {
+		config.Sidecar.Image = tailingSidecarImage
+	}
+
 	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
 		Scheme:             scheme,
 		MetricsBindAddress: metricsAddr,
@@ -84,7 +109,7 @@ func main() {
 	mgr.GetWebhookServer().Register("/add-tailing-sidecars-v1-pod", &webhook.Admission{
 		Handler: &handler.PodExtender{
 			Client:              mgr.GetClient(),
-			TailingSidecarImage: tailingSidecarImage,
+			TailingSidecarImage: config.Sidecar.Image,
 		},
 	})