azureblob: handle retry error codes more carefully

backend/azureblob/azureblob.go

@@ -656,13 +656,29 @@ func (f *Fs) shouldRetry(ctx context.Context, err error) (bool, error) {
 	if fserrors.ContextError(ctx, &err) {
 		return false, err
 	}
-	// FIXME interpret special errors - more to do here
+	var storageErr *azcore.ResponseError
-	if storageErr, ok := err.(*azcore.ResponseError); ok {
+	if errors.As(err, &storageErr) {
+		// General errors from:
+		// https://learn.microsoft.com/en-us/rest/api/storageservices/common-rest-api-error-codes
+		// Blob specific errors from:
+		// https://learn.microsoft.com/en-us/rest/api/storageservices/blob-service-error-codes
 		switch storageErr.ErrorCode {
 		case "InvalidBlobOrBlock":
 			// These errors happen sometimes in multipart uploads
 			// because of block concurrency issues
 			return true, err
+		case "InternalError":
+			// The server encountered an internal error. Please retry the request.
+			return true, err
+		case "OperationTimedOut":
+			// The operation could not be completed within the permitted time. The
+			// operation may or may not have succeeded on the server side. Please query
+			// the server state before retrying the operation.
+			return true, err
+		case "ServerBusy":
+			// The server is currently unable to receive requests. Please retry your
+			// request.
+			return true, err
 		}
 		statusCode := storageErr.StatusCode
 		for _, e := range retryErrorCodes {