Set proxy_cache_use_stale with PROXY_CACHE_USE_STALE environment variable

default value for this env variable is 'error timeout http_500 http_502 http_503 http_504'.
users can set their desired value for PROXY_CACHE_USE_STALE and configure their s3 gateway.

Author: mhbahmani

common/etc/nginx/nginx.conf

@@ -38,6 +38,7 @@ env PROXY_CACHE_VALID_OK;
 env PROXY_CACHE_SLICE_SIZE;
 env PROXY_CACHE_VALID_NOTFOUND;
 env PROXY_CACHE_VALID_FORBIDDEN;
+env PROXY_CACHE_USE_STALE;
 env HEADER_PREFIXES_TO_STRIP;
 env FOUR_O_FOUR_ON_EMPTY_BUCKET;
 env STRIP_LEADING_DIRECTORY_PATH;

common/etc/nginx/templates/default.conf.template

@@ -56,7 +56,7 @@ server {
     proxy_cache_revalidate on;
     proxy_cache_background_update on;
     proxy_cache_lock on;
-    proxy_cache_use_stale error timeout http_500 http_502 http_503 http_504;
+    proxy_cache_use_stale ${PROXY_CACHE_USE_STALE};
     proxy_cache_key "$request_method$host$uri";
 
     # If you need to support proxying range request, refer to this article: