Join Log in
Score:0
avatar Server

try_files seemingly looking in wrong directory

hu flag
FrankyBoy

I am trying to set up try_files, but am running into an issue: It seems the fallback "empty.png" file is not picked up, even though it is located at /path/to/old_cache_data/empty.png. The files that actually exist (i.e. no fallback) are found without problems. Also interesting enough I am not getting an nginx 404, but the 404 page from the app that is handled by the proxy_pass below.

Stuff I tried so far:

  • Removing the leading slash, which lead to this curious error: open() "/usr//htmlempty.png" failed (2: No such file or directory), Seems weird to me as /usr/html is not specified anywhere as any sort of fallback path.
  • Specifying an absolute path (i.e. try_files $uri /path/to/old_cache_data/empty.png;)

Relevant rules:

# legacy static cache
location /cache/ {
    root /path/to/old_cache_data;
    try_files $uri /empty.png;
}

# pass-through
location / {
    [bunch of proxy-settings]
    proxy_pass [the target url];
}

So, not sure where exactly I'm "holding it wrong". It seems like try_files does not pick up on the root in the location but somehow does a weird fallback.

EDIT: I found out that placing the empty.png in the "cache" sub-folder and changing the try_files to try_files $uri /cache/empty.png; actually works. I do not understand why this is the case though.

94
0 + 0
Score:1
Ivan Shatsky avatar Server
gr flag
Ivan Shatsky

As it stated by the documentation, last parameter of the try_files directive can be

  • a new URI;
  • HTTP error code: =code;
  • named location ID: @location_name.

You are using /empty.png which is treated as a new URI that does not fall under the location /cache { ... } thus being served by the location / { ... }. When you remove the leading slash you get the new URI empty.png that does not fall under any of your locations including location / { ... }. Every server block have some default root path prefix/html where prefix is specified at the compilation time and can be checked with the nginx -V command (looks like yours is /usr/). So as being said by the root directive documentation,

A path to the file is constructed by merely adding a URI to the value of the root directive.

which gives us prefix /usr/ + default root /html + URI empty.png = /usr//htmlempty.png.

When you change last try_files parameter to the /cache/empty.png, this URI is served with the same location /cache { ... } block with the file /path/to/old_cache_data + /cache/empty.png = /path/to/old_cache_data/cache/empty.png. And if you understand all the above information correctly, you should notice that with your configuration you can't access any files in the /path/to/old_cache_data folder except those in the /path/to/old_cache_data/cache subfolder. Check the difference between root and alias directives for better understanding.

0 + 0
hu flag
FrankyBoy
Aaaah that actually makes a lot of sense. Yeah I misunderstood it to simply be a file and didn't think about it as just another URL that gets re-evaluated. Thanks a lot :)
0
Reply
ธงชาติไทย
Elon Musk
I sit in a Tesla and translated this thread with Ai:

mangohost

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.