Let you point the Azure uploader at a custom endpoint

azure.go

@@ -54,13 +54,31 @@ type azureBLOBStorage struct {
 	serviceUrl string
 }
 
+// serviceURL returns the base blob service URL for the account. A custom
+// Endpoint (an Azurite emulator or a sovereign cloud such as
+// *.blob.core.chinacloudapi.cn) overrides the default global-cloud host.
+func (c *AzureConfig) serviceURL() (*url.URL, error) {
+	if c.Endpoint != "" {
+		return url.Parse(c.Endpoint)
+	}
+	return &url.URL{
+		Scheme: "https",
+		Host:   fmt.Sprintf("%s.blob.core.windows.net", c.AccountName),
+	}, nil
+}
+
 func NewAzure(conf *AzureConfig) (Storage, error) {
 	cred, err := azblob.NewSharedKeyCredential(conf.AccountName, conf.AccountKey)
 	if err != nil {
 		return nil, err
 	}
 
-	serviceUrl := fmt.Sprintf("https://%s.blob.core.windows.net/", conf.AccountName)
+	base, err := conf.serviceURL()
+	if err != nil {
+		return nil, err
+	}
+	serviceUrl := base.String()
+
 	client, err := azblob.NewClientWithSharedKeyCredential(serviceUrl, cred, nil)
 	if err != nil {
 		return nil, err
@@ -74,11 +92,12 @@ func NewAzure(conf *AzureConfig) (Storage, error) {
 }
 
 func (s *azureBLOBStorage) location(storagePath string) string {
-	return (&url.URL{
-		Scheme: "https",
-		Host:   fmt.Sprintf("%s.blob.core.windows.net", s.conf.AccountName),
-		Path:   path.Join(s.conf.ContainerName, storagePath),
-	}).String()
+	u, err := s.conf.serviceURL()
+	if err != nil {
+		return ""
+	}
+	u.Path = path.Join(u.Path, s.conf.ContainerName, storagePath)
+	return u.String()
 }
 
 func (s *azureBLOBStorage) UploadData(data []byte, storagePath, contentType string) (string, int64, error) {
@@ -218,12 +237,12 @@ func (s *azureBLOBStorage) GeneratePresignedUrl(storagePath string, expiration t
 		return "", err
 	}
 
-	loc := &url.URL{
-		Scheme:   "https",
-		Host:     fmt.Sprintf("%s.blob.core.windows.net", s.conf.AccountName),
-		Path:     path.Join(s.conf.ContainerName, storagePath),
-		RawQuery: qp.Encode(),
+	loc, err := s.conf.serviceURL()
+	if err != nil {
+		return "", err
 	}
+	loc.Path = path.Join(loc.Path, s.conf.ContainerName, storagePath)
+	loc.RawQuery = qp.Encode()
 	return loc.String(), nil
 }
 

config.go

@@ -37,7 +37,8 @@ type AzureConfig struct {
 	AccountName     string                 `yaml:"account_name,omitempty"` // (env AZURE_STORAGE_ACCOUNT)
 	AccountKey      string                 `yaml:"account_key,omitempty"`  // (env AZURE_STORAGE_KEY)
 	ContainerName   string                 `yaml:"container_name,omitempty"`
-	TokenCredential azcore.TokenCredential `yaml:"-"` // required for presigned url generation
+	Endpoint        string                 `yaml:"endpoint,omitempty"` // blob service URL; overrides the default https://<account>.blob.core.windows.net (e.g. an Azurite emulator or a sovereign cloud like *.blob.core.chinacloudapi.cn)
+	TokenCredential azcore.TokenCredential `yaml:"-"`                  // required for presigned url generation
 }
 
 func (c *AzureConfig) newStorage() (Storage, error) { return NewAzure(c) }

location_test.go

@@ -143,6 +143,38 @@ func TestAzureLocation(t *testing.T) {
 	}
 }
 
+func TestAzureLocationCustomEndpoint(t *testing.T) {
+	cases := []struct {
+		name        string
+		conf        AzureConfig
+		storagePath string
+		want        string
+	}{
+		{
+			name:        "azurite emulator preserves scheme and account path",
+			conf:        AzureConfig{AccountName: "devstoreaccount1", ContainerName: "mycontainer", Endpoint: "http://127.0.0.1:10000/devstoreaccount1"},
+			storagePath: "foo.mp4",
+			want:        "http://127.0.0.1:10000/devstoreaccount1/mycontainer/foo.mp4",
+		},
+		{
+			name:        "azurite emulator nested path",
+			conf:        AzureConfig{AccountName: "devstoreaccount1", ContainerName: "mycontainer", Endpoint: "http://127.0.0.1:10000/devstoreaccount1"},
+			storagePath: "a/b/c.mp4",
+			want:        "http://127.0.0.1:10000/devstoreaccount1/mycontainer/a/b/c.mp4",
+		},
+		{
+			name:        "sovereign cloud host",
+			conf:        AzureConfig{AccountName: "acct", ContainerName: "mycontainer", Endpoint: "https://acct.blob.core.chinacloudapi.cn"},
+			storagePath: "foo.mp4",
+			want:        "https://acct.blob.core.chinacloudapi.cn/mycontainer/foo.mp4",
+		},
+	}
+	for _, tc := range cases {
+		s := &azureBLOBStorage{conf: &tc.conf}
+		require.Equal(t, tc.want, s.location(tc.storagePath), tc.name)
+	}
+}
+
 func TestGCPLocation(t *testing.T) {
 	cases := []struct {
 		name        string