Handle configuration errors for Azure storage upfront

cmd/backup/command.go

@@ -36,6 +36,9 @@ func (c *command) runAsCommand() error {
 	}
 
 	for _, config := range configurations {
+		if err := config.validate(); err != nil {
+			return errwrap.Wrap(err, "error validating config")
+		}
 		if err := runScript(config); err != nil {
 			return errwrap.Wrap(err, "error running script")
 		}
@@ -101,6 +104,12 @@ func (c *command) schedule(strategy configStrategy) error {
 	}
 
 	for _, cfg := range configurations {
+		if err := cfg.validate(); err != nil {
+			return errwrap.Wrap(
+				err,
+				fmt.Sprintf("error validating config for schedule %s", cfg.BackupCronExpression),
+			)
+		}
 		config := cfg
 		id, err := c.cr.AddFunc(config.BackupCronExpression, func() {
 			c.logger.Info(

cmd/backup/config.go

@@ -12,6 +12,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob/blob"
 	"github.com/offen/docker-volume-backup/internal/errwrap"
 )
 
@@ -77,7 +78,7 @@ type Config struct {
 	AzureStorageContainerName     string                 `split_words:"true"`
 	AzureStoragePath              string                 `split_words:"true"`
 	AzureStorageEndpoint          string                 `split_words:"true" default:"https://{{ .AccountName }}.blob.core.windows.net/"`
-	AzureStorageAccessTier        string          `split_words:"true"`
+	AzureStorageAccessTier        AzureStorageAccessTier `split_words:"true"`
 	DropboxEndpoint               string                 `split_words:"true" default:"https://api.dropbox.com/"`
 	DropboxOAuth2Endpoint         string                 `envconfig:"DROPBOX_OAUTH2_ENDPOINT" default:"https://api.dropbox.com/"`
 	DropboxRefreshToken           string                 `split_words:"true"`
@@ -89,6 +90,13 @@ type Config struct {
 	additionalEnvVars             map[string]string
 }
 
+func (c *Config) validate() error {
+	if c.AzureStoragePrimaryAccountKey != "" && c.AzureStorageConnectionString != "" {
+		return errwrap.Wrap(nil, "using azure primary account key and connection string are mutually exclusive")
+	}
+	return nil
+}
+
 type CompressionType string
 
 func (c *CompressionType) Decode(v string) error {
@@ -180,6 +188,30 @@ func (n *WholeNumber) Int() int {
 	return int(*n)
 }
 
+type AzureStorageAccessTier string
+
+func (t *AzureStorageAccessTier) Decode(v string) error {
+	if v == "" {
+		*t = ""
+		return nil
+	}
+	for _, a := range blob.PossibleAccessTierValues() {
+		if string(a) == v {
+			*t = AzureStorageAccessTier(v)
+			return nil
+		}
+	}
+	return errwrap.Wrap(nil, fmt.Sprintf("%s is not a possible access tier value", v))
+}
+
+func (t *AzureStorageAccessTier) AccessTier() *blob.AccessTier {
+	if *t == "" {
+		return nil
+	}
+	a := blob.AccessTier(*t)
+	return &a
+}
+
 type envVarLookup struct {
 	ok    bool
 	key   string

cmd/backup/script.go

@@ -199,7 +199,7 @@ func (s *script) init() error {
 			Endpoint:          s.c.AzureStorageEndpoint,
 			RemotePath:        s.c.AzureStoragePath,
 			ConnectionString:  s.c.AzureStorageConnectionString,
-			AccessTier:        s.c.AzureStorageAccessTier,
+			AccessTier:        s.c.AzureStorageAccessTier.AccessTier(),
 		}
 		azureBackend, err := azure.NewStorageBackend(azureConfig, logFunc)
 		if err != nil {

internal/storage/azure/azure.go

@@ -39,15 +39,11 @@ type Config struct {
 	ConnectionString  string
 	Endpoint          string
 	RemotePath        string
-	AccessTier        string
+	AccessTier        *blob.AccessTier
 }
 
 // NewStorageBackend creates and initializes a new Azure Blob Storage backend.
 func NewStorageBackend(opts Config, logFunc storage.Log) (storage.Backend, error) {
-	if opts.PrimaryAccountKey != "" && opts.ConnectionString != "" {
-		return nil, errwrap.Wrap(nil, "using primary account key and connection string are mutually exclusive")
-	}
-
 	endpointTemplate, err := template.New("endpoint").Parse(opts.Endpoint)
 	if err != nil {
 		return nil, errwrap.Wrap(err, "error parsing endpoint template")
@@ -85,25 +81,11 @@ func NewStorageBackend(opts Config, logFunc storage.Log) (storage.Backend, error
 		}
 	}
 
-	var uploadStreamOptions *blockblob.UploadStreamOptions
-	if opts.AccessTier != "" {
-		var found bool
-		for _, t := range blob.PossibleAccessTierValues() {
-			if string(t) == opts.AccessTier {
-				found = true
-				uploadStreamOptions = &blockblob.UploadStreamOptions{
-					AccessTier: &t,
-				}
-			}
-		}
-		if !found {
-			return nil, errwrap.Wrap(nil, fmt.Sprintf("%s is not a possible access tier value", opts.AccessTier))
-		}
-	}
-
 	storage := azureBlobStorage{
 		client: client,
-		uploadStreamOptions: uploadStreamOptions,
+		uploadStreamOptions: &blockblob.UploadStreamOptions{
+			AccessTier: opts.AccessTier,
+		},
 		containerName: opts.ContainerName,
 		StorageBackend: &storage.StorageBackend{
 			DestinationPath: opts.RemotePath,