Add ws_log_format message directive

[zaslavskii]

1. Fixed bug when global variables remain dirty even though the nginx configuration is reloaded
2. Fixed a bug, when endpoint stops working if some directives are not filled: made directives optional
3. Log file defaults to current error_log file
4. Add ws_log_format "message" directive to log full messages, not chunks. Logged all non-control frames (https://tools.ietf.org/html/rfc6455#section-5.2).
5. Add ws_log_enabled to disable/enable module for the server block
6. Add ws_message_size template variable
7. Replaced global variables with srv configuration (http://nginx.org/en/docs/dev/development_guide.html#http_conf)

Some issues:

1. number of bytes sent when ws conn is opened is not logged. It's quite small and includes only headers.
2. The number of bytes logged only refer to the size of the payload:

USERMETRICS nd-123-456 rg-123-456 full ws_open 0 0 200 dedicated
FRAME 143 # this is what was sent - 143 bytes ({"jsonrpc": "2.0", "method":"eth_getBlockByHash","params":["0xb49c80c7d55fde1c7bb7385169c972442077f5fa9c5767332f83589e5ddb4ae8", true],"id": 1})
FRAME 170040 # this is what was received as a response (the full output will be quite heavy, this is a 170040 char json that ends with \n\n
FRAME 0
172.17.0.1 - - [20/Apr/2021:12:03:49 +0000] "GET / HTTP/1.1" 101 170050 223"-" "-" "-"

# 170050 223 - this is what nginx logs by default when ws is closed. I suppose it also includes headers and some non payload  data. I can spend some time understanding where this difference comes from, but I don't think if it worths it.

Example configuration

  server {
    listen 0.0.0.0:80;
    ws_log_enabled on;
    ws_log_format message "USERMETRICS nd-123-456 rg-123-456 full ws_open $ws_message_size 0 200 dedicated";
    ws_log_format open "USERMETRICS nd-123-456 rg-123-456 full ws_open 0 0 200 dedicated"; # or we can skip it completely, as we care only about the real payload 

Links:
https://tools.ietf.org/html/rfc6455#section-5.2
http://nginx.org/en/docs/dev/development_guide.html#http_conf

[fan-tom]

UB: you already dereferenced ctx, so it cannot be null here

[zaslavskii]

Thanks for that! I will change the condition as well as specify types of the arguments explicitly

UPD: can't change signatures of the functions as it will require significant refactoring

[fan-tom]

Earlier pointers were checked for null by simple negation. Don't you want to be consistent?

[fan-tom]

Suggested change

	if (conf->enabled && !conf->ws_log) {
	init_ws_log_file(cf, conf, &cf->cycle->error_log);
	}
	if (conf->enabled && !conf->ws_log)
	return NGX_CONF_ERROR;
	if (conf->enabled && !conf->ws_log->file)
	return NGX_CONF_ERROR;
	if (conf->enabled && !conf->ws_log) {
	init_ws_log_file(cf, conf, &cf->cycle->error_log);
	if (!conf->ws_log || !conf->ws_log->file)
	return NGX_CONF_ERROR;
	}