.. _config_http_conn_man_local_reply: Local reply modification ======================== The :ref:`HTTP connection manager ` supports modification of local reply which is response returned by Envoy itself. Features: * :ref:`Local reply content modification`. * :ref:`Local reply format modification`. .. _config_http_conn_man_local_reply_modification: Local reply content modification -------------------------------- The local response content returned by Envoy can be customized. A list of :ref:`mappers ` can be specified. Each mapper must have a :ref:`filter `. It may have following rewrite rules; a :ref:`status_code ` rule to rewrite response code, a :ref:`body ` rule to rewrite the local reply body and a :ref:`body_format_override ` to specify the response body format. Envoy checks each `mapper` according to the specified order until the first one is matched. If a `mapper` is matched, all its rewrite rules will apply. Example of a LocalReplyConfig .. code-block:: mappers: - filter: status_code_filter: comparison: op: EQ value: default_value: 400 runtime_key: key_b status_code: 401 body: inline_string: "not allowed" In above example, if the status_code is 400, it will be rewritten to 401, the response body will be rewritten to as "not allowed". .. _config_http_conn_man_local_reply_format: Local reply format modification ------------------------------- The response body content type can be customized. If not specified, the content type is plain/text. There are two `body_format` fields; one is the :ref:`body_format ` field in the :ref:`LocalReplyConfig ` message and the other :ref:`body_format_override ` field in the `mapper`. The latter is only used when its mapper is matched. The former is used if there is no any matched mappers, or the matched mapper doesn't have the `body_format` specified. Local reply format can be specified as :ref:`SubstitutionFormatString `. It supports :ref:`text_format ` and :ref:`json_format `. Example of a LocalReplyConfig with `body_format` field. .. code-block:: mappers: - filter: status_code_filter: comparison: op: EQ value: default_value: 400 runtime_key: key_b status_code: 401 body_format_override: text_format: "%LOCAL_REPLY_BODY% %REQ(:path)%" - filter: status_code_filter: comparison: op: EQ value: default_value: 500 runtime_key: key_b status_code: 501 body_format: text_format: "%LOCAL_REPLY_BODY% %RESPONSE_CODE%" In above example, there is a `body_format_override` inside the first `mapper` with a filter matching `status_code == 400`. It generates the response body in plain text format by concatenating %LOCAL_REPLY_BODY% with the `:path` request header. It is only used when the first mapper is matched. There is a `body_format` at the bottom of the config and at the same level as field `mappers`. It is used when non of the mappers is matched or the matched mapper doesn't have its own `body_format_override` specified.