instantiate a default cns config if loading fails (#1829)

Signed-off-by: Evan Baker <[email protected]>

cns/configuration/configuration.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/Azure/azure-container-networking/cns"
 	"github.com/Azure/azure-container-networking/cns/logger"
@@ -88,22 +89,22 @@ type KeyVaultSettings struct {
 	RefreshIntervalInHrs int
 }
 
-func getConfigFilePath(cmdLineConfigPath string) (string, error) {
-	// If config path is set from cmd line, return that
-	if cmdLineConfigPath != "" {
-		return cmdLineConfigPath, nil
+func getConfigFilePath(cmdPath string) (string, error) {
+	// If config path is set from cmd line, return that.
+	if strings.TrimSpace(cmdPath) != "" {
+		return cmdPath, nil
 	}
-
-	// Check if env set for config path otherwise use default path
-	configpath, found := os.LookupEnv(EnvCNSConfig)
-	if !found {
-		dir, err := common.GetExecutableDirectory()
-		if err != nil {
-			return "", errors.Wrap(err, "failed to discover exec dir for config")
-		}
-		configpath = filepath.Join(dir, defaultConfigName)
+	// If config path is set from env, return that.
+	if envPath := os.Getenv(EnvCNSConfig); strings.TrimSpace(envPath) != "" {
+		return envPath, nil
+	}
+	// otherwise compose the default config path and return that.
+	dir, err := common.GetExecutableDirectory()
+	if err != nil {
+		return "", errors.Wrap(err, "failed to discover exec dir for config")
 	}
-	return configpath, nil
+	defaultPath := filepath.Join(dir, defaultConfigName)
+	return defaultPath, nil
 }
 
 // ReadConfig returns a CNS config from file or an error.
@@ -112,18 +113,16 @@ func ReadConfig(cmdLineConfigPath string) (*CNSConfig, error) {
 	if err != nil {
 		return nil, err
 	}
-
-	logger.Printf("[Configuration] Config path:%s", configpath)
-
+	logger.Printf("[Configuration] Using config path: %s", configpath)
 	return readConfigFromFile(configpath)
 }
 
+// readConfigFromFile attempts to read the file and unmarshal it in to a CNSConfig.
 func readConfigFromFile(f string) (*CNSConfig, error) {
 	content, err := os.ReadFile(f)
 	if err != nil {
 		return nil, errors.Wrapf(err, "failed to read config file %s", f)
 	}
-
 	var config CNSConfig
 	if err := json.Unmarshal(content, &config); err != nil {
 		return nil, errors.Wrap(err, "failed to unmarshal config")

cns/service/main.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io/fs"
 	"net/http"
 	"os"
 	"os/signal"
@@ -42,7 +43,7 @@ import (
 	"github.com/Azure/azure-container-networking/crd/clustersubnetstate/api/v1alpha1"
 	"github.com/Azure/azure-container-networking/crd/nodenetworkconfig"
 	"github.com/Azure/azure-container-networking/crd/nodenetworkconfig/api/v1alpha"
-	"github.com/Azure/azure-container-networking/fs"
+	acnfs "github.com/Azure/azure-container-networking/internal/fs"
 	"github.com/Azure/azure-container-networking/log"
 	"github.com/Azure/azure-container-networking/nmagent"
 	"github.com/Azure/azure-container-networking/platform"
@@ -500,25 +501,28 @@ func main() {
 		logger.Errorf("[Azure CNS] Cannot disable telemetry via cmdline. Update cns_config.json to disable telemetry.")
 	}
 
-	logger.Printf("[Azure CNS] cmdLineConfigPath: %s", cmdLineConfigPath)
 	cnsconfig, err := configuration.ReadConfig(cmdLineConfigPath)
 	if err != nil {
-		logger.Errorf("[Azure CNS] Error reading cns config: %v", err)
+		if errors.Is(err, fs.ErrNotExist) {
+			logger.Warnf("config file does not exist, using default")
+			cnsconfig = &configuration.CNSConfig{}
+		} else {
+			logger.Errorf("fatal: failed to read cns config: %v", err)
+			os.Exit(1)
+		}
 	}
-
 	configuration.SetCNSConfigDefaults(cnsconfig)
-	logger.Printf("[Azure CNS] Read config :%+v", cnsconfig)
+	logger.Printf("[Azure CNS] Using config: %+v", cnsconfig)
 
 	_, envEnableConflistGeneration := os.LookupEnv(envVarEnableCNIConflistGeneration)
-
 	var conflistGenerator restserver.CNIConflistGenerator
 	if cnsconfig.EnableCNIConflistGeneration || envEnableConflistGeneration {
 		conflistFilepath := cnsconfig.CNIConflistFilepath
 		if cniConflistFilepathArg != "" {
 			// allow the filepath to get overidden by command line arg
 			conflistFilepath = cniConflistFilepathArg
 		}
-		writer, newWriterErr := fs.NewAtomicWriter(conflistFilepath)
+		writer, newWriterErr := acnfs.NewAtomicWriter(conflistFilepath)
 		if newWriterErr != nil {
 			logger.Errorf("unable to create atomic writer to generate cni conflist: %v", newWriterErr)
 			os.Exit(1)

fs/atomic_test.go → internal/fs/atomic_test.go

@@ -5,7 +5,7 @@ import (
 	"os"
 	"testing"
 
-	"github.com/Azure/azure-container-networking/fs"
+	"github.com/Azure/azure-container-networking/internal/fs"
 	"github.com/stretchr/testify/require"
 )