Prioritize `X-Accel-Expires` than `Cache-Control` and `Expires` (#964)

[Yugo Horie]

changeset:   7997:86f70e48a64a
branch:      issue-964
tag:         tip
user:        Yugo Horie <yugo-horie at jocdn.co.jp>
date:        Tue Jan 25 12:16:05 2022 +0900
files:       src/http/ngx_http_upstream.c src/http/ngx_http_upstream.h
description:
Prioritize `X-Accel-Expires` than `Cache-Control` and `Expires` (#964)

We introduce 3 flags that indicate to be overwriting cache control behavior.

* The `overwrite_noncache` switches on the case of not to be cached when
processing `Cache-Control` and `Expires` headers from upstream.

* The `overwrite_stale_xxx` flags also switch on when it's enabled to use
stale cache behavior on processing those headers.

* `process_accel_expires` watches these flags, which invalidates their non-
cache
and stale behavior which had been set in other headers to prioritize
`X-Accel-Expires`.

user: Yugo Horie <yugo-horie at jocdn.co.jp>
changed src/http/ngx_http_upstream.c
changed src/http/ngx_http_upstream.h


diff -r 5d88e2bf92b3 -r 86f70e48a64a src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c      Sat Jan 22 00:28:51 2022 +0300
+++ b/src/http/ngx_http_upstream.c      Tue Jan 25 12:16:05 2022 +0900
@@ -4747,6 +4747,7 @@
         || ngx_strlcasestrn(start, last, (u_char *) "private", 7 - 1) !=
NULL)
     {
         u->cacheable = 0;
+        u->overwrite_noncache = 1;
         return NGX_OK;
     }

@@ -4772,11 +4773,13 @@
             }

             u->cacheable = 0;
+            u->overwrite_noncache = 1;
             return NGX_OK;
         }

         if (n == 0) {
             u->cacheable = 0;
+            u->overwrite_noncache = 1;
             return NGX_OK;
         }

@@ -4800,9 +4803,12 @@
             }

             u->cacheable = 0;
+            u->overwrite_noncache = 1;
             return NGX_OK;
         }

+        u->overwrite_stale_updating = 1;
+        u->overwrite_stale_error = 1;
         r->cache->updating_sec = n;
         r->cache->error_sec = n;
     }
@@ -4822,10 +4828,12 @@
                 continue;
             }

+            u->overwrite_noncache = 1;
             u->cacheable = 0;
             return NGX_OK;
         }

+        u->overwrite_stale_error = 1;
         r->cache->error_sec = n;
     }
     }
@@ -4863,6 +4871,7 @@
     expires = ngx_parse_http_time(h->value.data, h->value.len);

     if (expires == NGX_ERROR || expires < ngx_time()) {
+        u->overwrite_noncache = 1;
         u->cacheable = 0;
         return NGX_OK;
     }
@@ -4897,6 +4906,15 @@
     if (r->cache == NULL) {
         return NGX_OK;
     }
+    if (u->overwrite_noncache) {
+        u->cacheable = 1;
+    }
+    if (u->overwrite_stale_updating) {
+        r->cache->updating_sec = 0;
+    }
+    if (u->overwrite_stale_error) {
+        r->cache->error_sec = 0;
+    }

     len = h->value.len;
     p = h->value.data;
diff -r 5d88e2bf92b3 -r 86f70e48a64a src/http/ngx_http_upstream.h
--- a/src/http/ngx_http_upstream.h      Sat Jan 22 00:28:51 2022 +0300
+++ b/src/http/ngx_http_upstream.h      Tue Jan 25 12:16:05 2022 +0900
@@ -386,6 +386,9 @@

     unsigned                         store:1;
     unsigned                         cacheable:1;
+    unsigned                         overwrite_noncache:1;
+    unsigned                         overwrite_stale_updating:1;
+    unsigned                         overwrite_stale_error:1;
     unsigned                         accel:1;
     unsigned                         ssl:1;
 #if (NGX_HTTP_CACHE)
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