nginx logs for location - nginx

Question

Need some help in setting up nginx logs so that they are not duplicated.
My configuration is as following. What I would like to achieve is that all logs for say, http://example.com/app goes to file app.access.log and logs for rest of the site goes to file main.access.log
However, following configuration logs app logs to both, app.access.log and main.access.log.
server {
access_log /var/log/nginx/main.access.log;
location /app {
access_log /var/log/nginx/app.access.log;
}
}
Any idea how to fix this?

Answer 1

You could use a negation regexp to intercept all request NOT directed to app, and define there the access_log directive. Then define the other location for app
location ~ ^((?!app).)*$ {
access_log /var/log/nginx/not-an-app.access.log;
}
location /app {
access_log /var/log/nginx/app.access.log;
}
I think it's a bit of a stretch though, and i would test the hell out of this before putting it in production.

Answer 2

The access_log directive includes an if=condition which can be used to control logging.
For example:
map $request_uri $loggable {
~^/app 0;
default 1;
}
server {
access_log /var/log/nginx/main.access.log if=$loggable;
...
}
See this document for details.
The alternative is to log everything together and split it into two separate files later using grep.
Inspired by #Andrea's solution, you could also use this pattern:
server {
location / {
access_log /var/log/nginx/main.access.log;
location /foo { ... }
location /bar { ... }
...
}
location /app {
access_log /var/log/nginx/app.access.log;
}
}
So the top level has just two top level location blocks, and all other location blocks are nested within the default `location.