Cowboy access log

Description

This app implements apache-styled access logging for cowboy >= 2.0.
It works as a stream handler and logs every request received by server via Logger.
Following information is being logged:

• status - HTTP status code
• remote_addr - IP address of request origin if it was forwarded
• peer_addr - IP address of request origin
• request_method - Request method
• request_path - Request path
• request_length - Request length
• response_length - Responce length
• request_time - Time taken by requset proccessing in µs
• http_x-request-id - Unique request id

cowboy_access_log also supports custom meta, that can be added by calling set_extra_info_fun/2 on your Cowboy options.
extra_info_fun must take Req as it's only argument and return #{atom() => term()}.

Usage

To use this stream handler just put it in stream handler chain when configuring cowboy server. All log events, created by the handler are being taged with cowboy_access_log domain, so they can be easily filtered with built-in functions. Check examples for better understanding.

Examples

Add handler

cowboy:start_clear(http, [{port, 8080}], #{
    stream_handlers => [cowboy_access_log, cowboy_stream_h],
    env => #{dispatch => Dispatch}
}).

Filter only cowboy_access_log events

add_handler_filter(
    HandlerId,
    FilterId,
    {fun logger_filters:domain/2, {stop, not_equal, [cowboy_access_log]}}
).

Add function to tag each log event with random Id

CowboyOpts0 = #{
    stream_handlers => [cowboy_access_log, cowboy_stream_h],
    env => #{dispatch => Dispatch}
},
CowboyOpts = cowboy_access_log_h:set_extra_info_fun(fun(_Req) -> #{my_random_id => base64:encode(crypto:strong_rand_bytes(20))} end, CowboyOpts0),
cowboy:start_clear(http, [{port, 8080}], CowboyOpts).