I am new to nginx caching but have worked with nginx a lot. I tried enabling caching feature in our repository but it never worked so I thought I will pull a fresh copy of nginx and turn it on. I ended with the same issue. For some reason, nginx is not able to create the cache file in the cache dir. I have already turned on proxy buffering and set full rw permission for all users on the cache dir. I also gdb'ed the code and it seems like it gets into ngx_open_and_stat_file from ngx_open_cached_file ( http://lxr.nginx.org/source/src/core/ngx_open_file_cache.c?v=nginx-1.12.0#0144 ) and it tries to open an non existent file in RDONLY mode if the of->log is not set ( http://lxr.nginx.org/source/src/core/ngx_open_file_cache.c?v=nginx-1.12.0#0869 )

Any help here would be awesome. I have also pasted my relevant config and debug log below.

Here's my configuration.. (only the relevant part)

http {

proxy_cache_path /tmp/nginx/cache levels=1:2 keys_zone=STATIC:10m
inactive=24h max_size=1g;

server {
listen 80;
server_name localhost;
proxy_buffering on;

location / {
proxy_pass http://52.216.66.40$request_uri;
proxy_set_header Host images.clipartpanda.com;
proxy_buffering on;
proxy_cache STATIC;
add_header X-Proxy-Cache $upstream_cache_status;
root html;
index index.html index.htm;
}
}

And here's the debug log showing whats that nginx is failing to create the cache file.
2018/02/05 08:57:26 [debug] 22509#0: *7 http cache key: "http://52.216.66.40"
2018/02/05 08:57:26 [debug] 22509#0: *7 http cache key: "/teddy-clip-art-teddy-md.png"
2018/02/05 08:57:26 [debug] 22509#0: *7 add cleanup: 00000000006D3560
2018/02/05 08:57:26 [debug] 22509#0: shmtx lock
2018/02/05 08:57:26 [debug] 22509#0: slab alloc: 120 slot: 4
2018/02/05 08:57:26 [debug] 22509#0: slab alloc: 00007FD2C31AA080
2018/02/05 08:57:26 [debug] 22509#0: shmtx unlock
2018/02/05 08:57:26 [debug] 22509#0: *7 http file cache exists: -5 e:0
2018/02/05 08:57:26 [debug] 22509#0: *7 cache file: "/tmp/nginx/cache/3/4f/ecbc29d001e852b40f09e913b5ced4f3"
2018/02/05 08:57:26 [debug] 22509#0: *7 add cleanup: 00000000006D35B0
2018/02/05 08:57:26 [debug] 22509#0: *7 http upstream cache: -5

And for now i have set "777" perm to the nginx cache dir.

>> ls -lrt /tmp/nginx/
drwxrwxrwx 2 test root 4096 Feb 5 08:20 cache