[PATCH] skip apply "ngx_http_upstream_process_accel_expires" when a request responeded by cache

[TAKADA Sokichi]

# HG changeset patch
# User TAKADA Sokichi <takada at jocdn.co.jp>
# Date 1592383243 -32400
#      Wed Jun 17 17:40:43 2020 +0900
# Node ID d5bbe3ad1f1491125485786aacc5d219c81801d1
# Parent  8cf31489b479b689b7ff4a9601ce24c914d0394c
skip apply "ngx_http_upstream_process_accel_expires" when a request responeded by cache

"ngx_http_upstream_process_accel_expires" is calculate and set valid_date value when a request respond by a cache, even though it will never use in the response.
This patch to skip unnecessary process.

On the other hands, this has good side effect to can get TRUE valid_date value of the cache file in "header filter" and "log" hook handler.
i.e. I would like to get the TRUE valid_date of cache in header_filter_by_lua or log_by_lua handlers.

diff -r 8cf31489b479 -r d5bbe3ad1f14 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c	Mon Jun 15 17:35:26 2020 -0400
+++ b/src/http/ngx_http_upstream.c	Wed Jun 17 17:40:43 2020 +0900
@@ -4776,6 +4776,10 @@
         return NGX_OK;
     }
 
+    if (r->cached == 1) {
+        return NGX_OK;
+    }
+
     len = h->value.len;
     p = h->value.data;