Merge pull request #146 from AmitKumarDas/code-39

feat(command): add command cr that creates a k8s job

cmd/commander/main.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/pkg/errors"
 	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@@ -39,33 +40,38 @@ import (
 var (
 	commandKind = flag.String(
 		"command-kind",
-		"Command",
-		"Kind of Command custom resource",
+		"Command", // default
+		"Kubernetes custom resource kind",
 	)
+
 	commandResource = flag.String(
 		"command-resource",
-		"commands",
-		"Resource name of Command custom resource",
+		"commands", // default
+		"Kubernetes custom resource name",
 	)
+
 	commandGroup = flag.String(
 		"command-group",
-		"dope.metacontroller.io",
-		"Group of Command custom resource",
+		"dope.metacontroller.io", // default
+		"Kubernetes custom resource group",
 	)
+
 	commandVersion = flag.String(
-		"command-version",
-		"v1",
-		"Version of Command custom resource",
+		"command-api-version",
+		"v1", // default
+		"Kubernetes custom resource api version",
 	)
+
 	commandName = flag.String(
 		"command-name",
 		"",
-		"Name of Command custom resource",
+		"Name of the command",
 	)
+
 	commandNamespace = flag.String(
 		"command-ns",
 		"",
-		"Namespace of Command custom resource",
+		"Namespace of the command",
 	)
 
 	kubeAPIServerURL = flag.String(
@@ -74,24 +80,29 @@ var (
 		`Kubernetes api server url (same format as used by kubectl).
 		If not specified, uses in-cluster config`,
 	)
+
 	kubeconfig *string
 
 	clientGoQPS = flag.Float64(
 		"client-go-qps",
-		5,
+		5, // default
 		"Number of queries per second client-go is allowed to make (default 5)",
 	)
+
 	clientGoBurst = flag.Int(
 		"client-go-burst",
-		10,
+		10, // default
 		"Allowed burst queries for client-go (default 10)",
 	)
 )
 
-// main function is the entry point of this binary.
+// This is the entry point of this binary
 //
 // This binary is meant to be run to completion. In other
 // words this does not expose any long running service.
+// This executes the commands or scripts specified in the
+// custom resource and updates this resource post execution.
+//
 //
 // NOTE:
 //	A kubernetes **Job** can make use of this binary
@@ -127,45 +138,71 @@ func main() {
 	defer klog.Flush()
 
 	if *commandName == "" {
-		klog.Fatal("Invalid arguments: Flag 'command-name' must be set")
+		klog.Exit("Invalid arguments: Flag 'command-name' must be set")
+	}
+	if *commandNamespace == "" {
+		klog.Exit("Invalid arguments: Flag 'command-ns' must be set")
 	}
 
-	klog.V(1).Infof("Command custom resource: kind %s", *commandKind)
-	klog.V(1).Infof("Command custom resource: resource %s", *commandResource)
-	klog.V(1).Infof("Command custom resource: group %s", *commandGroup)
-	klog.V(1).Infof("Command custom resource: version %s", *commandVersion)
-	klog.V(1).Infof("Command custom resource: name %s", *commandName)
-	klog.V(1).Infof("Command custom resource: namespace %s", *commandNamespace)
+	klog.V(1).Infof("Command custom resource: group %q", *commandGroup)
+	klog.V(1).Infof("Command custom resource: version %q", *commandVersion)
+	klog.V(1).Infof("Command custom resource: kind %q", *commandKind)
+	klog.V(1).Infof("Command custom resource: resource %q", *commandResource)
+	klog.V(1).Infof("Command custom resource: namespace %q", *commandNamespace)
+	klog.V(1).Infof("Command custom resource: name %q", *commandName)
 
-	runCommand(getRestConfig())
+	r, err := NewRunner()
+	if err != nil {
+		// This should lead to crashloopback if this
+		// is running from within a Kubernetes pod
+		klog.Exit(err)
+	}
+	err = r.Run()
+	if err != nil {
+		// This should lead to crashloopback if this
+		// is running from within a Kubernetes pod
+		klog.Exit(err)
+	}
 	os.Exit(0)
 }
 
-func getRestConfig() *rest.Config {
+// Runnable helps in executing the Kubernetes command resource.
+// It does so by executing the commands or scripts specified in
+// the resource and updating this resource post execution.
+type Runnable struct {
+	Client dynamic.Interface
+	GVR    schema.GroupVersionResource
+
+	commandStatus *types.CommandStatus
+}
+
+// NewRunner returns a new instance of Runnable
+func NewRunner() (*Runnable, error) {
 	var config *rest.Config
 	var err error
+
 	if *kubeconfig != "" {
-		klog.V(1).Infof("Using kubeconfig %s", *kubeconfig)
+		klog.V(2).Infof("Using kubeconfig %q", *kubeconfig)
 		config, err = clientcmd.BuildConfigFromFlags("", *kubeconfig)
 	} else if *kubeAPIServerURL != "" {
-		klog.V(1).Infof("Using kubernetes api server url %s", *kubeAPIServerURL)
+		klog.V(2).Infof("Using kubernetes api server url %q", *kubeAPIServerURL)
 		config, err = clientcmd.BuildConfigFromFlags(*kubeAPIServerURL, "")
 	} else {
-		klog.V(1).Info("Using in-cluster kubeconfig")
+		klog.V(2).Info("Using in-cluster kubeconfig")
 		config, err = rest.InClusterConfig()
 	}
 	if err != nil {
-		klog.Fatal(err)
+		return nil, err
 	}
+
+	// configure kubernetes client config with additional settings
+	// to manage deluge of requests to kubernetes API server
 	config.QPS = float32(*clientGoQPS)
 	config.Burst = *clientGoBurst
-	return config
-}
 
-func runCommand(config *rest.Config) {
 	client, err := dynamic.NewForConfig(config)
 	if err != nil {
-		klog.Fatal(err)
+		return nil, err
 	}
 
 	gvr := schema.GroupVersionResource{
@@ -174,77 +211,166 @@ func runCommand(config *rest.Config) {
 		Resource: *commandResource,
 	}
 
-	got, err := client.Resource(gvr).
+	return &Runnable{
+		Client: client,
+		GVR:    gvr,
+	}, nil
+}
+
+func (a *Runnable) updateWithRetries() error {
+	var statusNew interface{}
+	err := unstruct.MarshalThenUnmarshal(a.commandStatus, &statusNew)
+	if err != nil {
+		return errors.Wrapf(
+			err,
+			"Marshal unmarshal failed: Command %q %q",
+			*commandNamespace,
+			*commandName,
+		)
+	}
+
+	// Command is updated with latest labels
+	labels := map[string]string{
+		// this label key is set with same value as that of status.phase
+		types.LblKeyCommandPhase: string(a.commandStatus.Phase),
+	}
+
+	var runtimeErr error
+
+	// This uses exponential backoff to avoid exhausting
+	// the apiserver
+	retryErr := retry.RetryOnConflict(
+		retry.DefaultRetry,
+		func() error {
+			// Retrieve the latest version of Command
+			cmd, err := a.Client.
+				Resource(a.GVR).
+				Namespace(*commandNamespace).
+				Get(*commandName, v1.GetOptions{})
+			if err != nil {
+				// Retry this error since this might be a temporary
+				return errors.Wrapf(
+					err,
+					"Failed to get command: %q %q",
+					*commandNamespace,
+					*commandName,
+				)
+			}
+
+			// Mutate command resource's status field
+			err = unstructured.SetNestedField(
+				cmd.Object,
+				statusNew,
+				"status",
+			)
+			if err != nil {
+				runtimeErr = errors.Wrapf(
+					err,
+					"Set unstruct failed: Command %q %q",
+					*commandNamespace,
+					*commandName,
+				)
+				// Return nil to avoid retry
+				//
+				// NOTE:
+				//	Setting unstructured instance should not be
+				// retried since every retry will result in the
+				// same error
+				return nil
+			}
+
+			// Merge existing labels with desired pair(s)
+			unstruct.SetLabels(cmd, labels)
+
+			updated, err := a.Client.
+				Resource(a.GVR).
+				Namespace(*commandNamespace).
+				Update(cmd, v1.UpdateOptions{})
+
+			if err != nil {
+				// Update error is returned to be retried since this
+				// might be temporary
+				return errors.Wrapf(
+					err,
+					"Update failed: Command %q %q",
+					*commandNamespace,
+					*commandName,
+				)
+			}
+
+			// Mutate command instance with latest resource version
+			// before trying update status. This is done since previous
+			// update would have modified resource version.
+			cmd.SetResourceVersion(updated.GetResourceVersion())
+			// Update command status as a **sub resource** update
+			_, err = a.Client.
+				Resource(a.GVR).
+				Namespace(*commandNamespace).
+				UpdateStatus(cmd, v1.UpdateOptions{})
+
+			// If update status resulted in an error it will be
+			// returned so that update can be retried
+			return errors.Wrapf(
+				err,
+				"Update status failed: Command %q %q",
+				*commandNamespace,
+				*commandName,
+			)
+		})
+
+	if runtimeErr != nil {
+		return errors.Wrapf(
+			runtimeErr,
+			"Update failed: Runtime error: Command: %q %q",
+			*commandNamespace,
+			*commandName,
+		)
+	}
+	return retryErr
+}
+
+// Run executes the command resource
+func (a *Runnable) Run() error {
+	got, err := a.Client.
+		Resource(a.GVR).
 		Namespace(*commandNamespace).
 		Get(
 			*commandName,
 			v1.GetOptions{},
 		)
 	if err != nil {
-		klog.Fatal(err)
+		return errors.Wrapf(
+			err,
+			"Failed to get command: %q %q",
+			*commandNamespace,
+			*commandName,
+		)
 	}
 
 	var c types.Command
 	// convert from unstructured instance to typed instance
 	err = unstruct.ToTyped(got, &c)
 	if err != nil {
-		klog.Fatal(err)
+		return errors.Wrapf(
+			err,
+			"Failed to convert unstructured to typed instance: %q %q",
+			*commandNamespace,
+			*commandName,
+		)
 	}
 
-	cmder, err := command.NewCommander(
-		command.CommandableConfig{
-			Command: &c,
+	cmdRunner, err := command.NewRunner(
+		command.RunnableConfig{
+			Command: c,
 		},
 	)
 	if err != nil {
-		klog.Fatal(err)
+		return err
 	}
-	status, err := cmder.Run()
+	a.commandStatus, err = cmdRunner.Run()
 	if err != nil {
-		klog.Fatal(err)
+		return err
 	}
 
-	retryErr := retry.RetryOnConflict(retry.DefaultRetry, func() error {
-		// Retrieve the latest version of Command before attempting update
-		// RetryOnConflict uses exponential backoff to avoid exhausting the apiserver
-		got, err = client.Resource(gvr).
-			Namespace(*commandNamespace).
-			Get(
-				*commandName,
-				v1.GetOptions{},
-			)
-		if err != nil {
-			klog.Fatal(err)
-		}
-
-		// update labels
-		lbls := got.GetLabels()
-		if len(lbls) == 0 {
-			lbls = make(map[string]string)
-		}
-		lbls["command.dope.metacontroller.io/phase"] = string(status.Phase)
-		got.SetLabels(lbls)
-
-		// update status
-		err = unstructured.SetNestedField(
-			got.Object,
-			status,
-			"status",
-		)
-		if err != nil {
-			klog.Fatal(err)
-		}
-
-		// update command resource
-		_, updateErr := client.Resource(gvr).
-			Namespace(*commandNamespace).
-			Update(
-				got,
-				v1.UpdateOptions{},
-			)
-		return updateErr
-	})
-	if retryErr != nil {
-		klog.Fatal(retryErr)
-	}
+	return a.updateWithRetries()
 }