make ngnix log stackdriver compatible json (Netflix#74)

* make ngnix log stackdriver compatible json
* add severity, log name and more

Co-authored-by: Mattias Springare <mspringare@spotify.com>

nginx.conf

@@ -2,9 +2,38 @@ add_header X-Frame-Options DENY;
 add_header X-Content-Type-Options nosniff;
 add_header X-XSS-Protection "1; mode=block";
 
+map $time_iso8601 $time_iso8601_p1 {
+    ~([^+]+) $1;
+}
+
+map $msec $millisec {
+    ~\.([0-9]+)$ $1;
+}
+
+log_format json_combined
+'{'
+    '"timestamp":"$time_iso8601_p1.${millisec}000",'
+    '"severity":"INFO",'
+    '"log":"ngnix",'
+    '"httpRequest":{'
+    '"requestMethod":"$request_method",'
+    '"requestUrl":"$scheme://$host$request_uri",'
+    '"requestSize":$request_length,'
+    '"status":$status,'
+    '"responseSize":$bytes_sent,'
+    '"userAgent":"$http_user_agent",'
+    '"remote_addr":"$remote_addr",'
+    '"remoteIp":"$http_x_forwarded_for",'
+    '"serverIp":"$server_addr",'
+    '"referer":"$http_referer",'
+    '"latency":"${request_time}s",'
+    '"protocol":"$server_protocol"'
+    '}'
+'}';
+
 server {
    listen      80;
-   access_log  /dev/stdout;
+   access_log  /dev/stdout  json_combined;
    error_log   /dev/stderr;
 
    location /api {
@@ -23,4 +52,4 @@ server {
         index index.html;
     }
 
-}
+}