Several third-party module directives allows direct jump to named location, e.g.
ngx.exec from the lua-nginx-module or
echo_exec from the echo-nginx-module (both modules are bundled with the OpenResty package). However using the "vanilla" nginx the only way to do it is to use the
try_files directive trick. Unfortunately the @VictorSchröder assumption of using
/dev/null as the
try_files argument will eliminate the performance penalty due to the system
stat call is wrong, it is the
/webroot/dev/null file that will be
stat'ed in that case. Everyone can check it and see for themselves using the following instruction. So it makes no difference with the commonly used solution like
try_files /nonexistent @app;
However it is possible to pass an empty sting as the
try_files "" @app;
This will not eliminate the
stat system call. However it is the webroot directory that will be
stat'ed in this case and checked to be an existing physical file on your filesystem, what it most likely isn't (well, at least unless you point your server or location root to such a file, but why would you do such a wild thing?) By my assumption, modern kernels should cache
stat system call results for the existing filesystem objects more effectively than for non-existing ones. This is only an assumption, so if someone reading this knows better how kernel behaves in this situation, I'll be glad to listen for any clarifications.
I think the last part needs some clarification. Why the
try_files directive checks the web root to be a physical file and not a directory? That's because the
"" argument is not ended with a slash. An argument ended with a slash makes
try_files testing it to be a directory, and an argument not ended with a slash makes
try_files testing it to be a file. That is, the
try_files "/" ... first check will always succeed (and an explicit or implicit
index directive will take a job for an index file searching on the next request processing stage, assuming the location has static content handler) if the location root is pointing to the existing directory, and the
try_files "" ... first check will always fail in that case.
It is also possible that the server webroot would be a non-existent directory, for example when nginx is used for reverse proxying only. Like many other nginx directives the
root directive, if not being inherited from the previous configuration levels, has a default value of
/html relative to the nginx prefix. That prefix is specified during the build time and can be checked with the
nginx -V command (see the
--prefix=... configure argument). If by example this prefix is equal to
/etc/nginx (a common case), the default server webroot will be
/etc/nginx/html which is unlikely to be an existing directory for most environments.
Still I'd prefer
try_files "" ... rather that
try_files /nonexistent .... If by any mean the
nonexistent file will appear in the webroot directory (think about some kind of defacing hacker attack), the first one will continue to work while the second one will not.
There can be use cases for the
try_files "" ... construction when the webroot directory is specified using the
alias directive, especially for the exact or regex matching locations. However I can't see any possible use case for it being placed inside the location using
root one, so I think nginx development team may consider to update the
try_files module source code to totally eliminate that extra
stat call in case of such a usage. It will made possible "unconditional" location jumps without any extra performance penalty at all while keeping compatibility with the any existing configuration.