More detail in NGINX error logs · Dec 5, 21:38 by Shannon Wynter

Where I’m working now we have a rather complicated internal structure to our rather large web application and it’s sometime super hard to track down the problem – especially if a request triggers an API call.

I’ve modified our frontend configuration to pass a X-Trace-ID and all our logging/servers to include that trace id in any given request

	set $tid $pid-$msec-$remote_addr-$connection-$request_id;
	if ($http_x_trace_id) {
		set $tid $http_x_trace_id;
	}
 	proxy_set_header X-Trace-ID $tid;
	fastcgi_param HTTP_X_TRACE_ID $tid;

Except when it comes to error logs, if anything goes wrong with a proxied request, we’re out of luck – well not any more :D

1. diff -dur nginx-1.11.6.org/src/http/ngx_http_request.c nginx-1.11.6/src/http/ngx_http_request.c
2. --- nginx-1.11.6.org/src/http/ngx_http_request.c2016-11-16 01:11:47.000000000 +1000
3. +++ nginx-1.11.6/src/http/ngx_http_request.c2016-12-05 21:18:16.000000000 +1000
4. @@ -118,6 +118,10 @@
5.                   offsetof(ngx_http_headers_in_t, content_type),
6.                   ngx_http_process_header_line },
7.   
8. +    { ngx_string("X-Trace-ID"),
9. +                 offsetof(ngx_http_headers_in_t, x_trace_id),
10. +                 ngx_http_process_header_line },
11. +
12.      { ngx_string("Range"), offsetof(ngx_http_headers_in_t, range),
13.                   ngx_http_process_header_line },
14.   
15. @@ -3656,5 +3660,11 @@
16.          buf = p;
17.      }
18.   
19. +    if (r->headers_in.x_trace_id) {
20. +        p = ngx_snprintf(buf, len, ", trace_id: \"%V\"",
21. +                         &r->headers_in.x_trace_id->value);
22. +        buf = p;
23. +    }
24. +
25.      return buf;
26. }
27. diff -dur nginx-1.11.6.org/src/http/ngx_http_request.h nginx-1.11.6/src/http/ngx_http_request.h
28. --- nginx-1.11.6.org/src/http/ngx_http_request.h2016-11-16 01:11:47.000000000 +1000
29. +++ nginx-1.11.6/src/http/ngx_http_request.h2016-12-05 21:33:07.000000000 +1000
30. @@ -185,6 +185,7 @@
31.      ngx_table_elt_t                  *content_length;
32.      ngx_table_elt_t                  *content_range;
33.      ngx_table_elt_t                  *content_type;
34. +    ngx_table_elt_t                  *x_trace_id;
35.   
36.      ngx_table_elt_t                  *range;
37.      ngx_table_elt_t                  *if_range;
38.  
39. Download this code: nginx_trace_id.1.11.6.patch (Downloaded 1087 time(s))

Apply this patch to nginx-1.11.6 and X-Trace-ID will appear in your logs if it’s available

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