[PATCH] Upstream: add $upstream_cache_age variable

[Piotr Sikora]

# HG changeset patch
# User Piotr Sikora <piotr at cloudflare.com>
# Date 1412284916 25200
#      Thu Oct 02 14:21:56 2014 -0700
# Node ID 488aa8f86041dbe99a8f8ebbb3df533b9ce3e19e
# Parent  a215d9021f137b9e2d4f69c37c7f992a2bef12c6
Upstream: add $upstream_cache_age variable.

This variable represents the amount of time that passed since the response
was fetched (or successfully revalidated) from the upstream server.

Signed-off-by: Piotr Sikora <piotr at cloudflare.com>

diff -r a215d9021f13 -r 488aa8f86041 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c	Tue Sep 30 17:20:33 2014 +0400
+++ b/src/http/ngx_http_upstream.c	Thu Oct 02 14:21:56 2014 -0700
@@ -21,6 +21,8 @@ static ngx_int_t ngx_http_upstream_cache
     ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_http_upstream_cache_etag(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
+static ngx_int_t ngx_http_upstream_cache_age(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
 #endif
 
 static void ngx_http_upstream_init_request(ngx_http_request_t *r);
@@ -373,6 +375,10 @@ static ngx_http_variable_t  ngx_http_ups
       ngx_http_upstream_cache_etag, 0,
       NGX_HTTP_VAR_NOCACHEABLE|NGX_HTTP_VAR_NOHASH, 0 },
 
+    { ngx_string("upstream_cache_age"), NULL,
+      ngx_http_upstream_cache_age, 0,
+      NGX_HTTP_VAR_NOCACHEABLE|NGX_HTTP_VAR_NOHASH, 0 },
+
 #endif
 
     { ngx_null_string, NULL, NULL, 0, 0, 0 }
@@ -4851,6 +4857,32 @@ ngx_http_upstream_cache_etag(ngx_http_re
     return NGX_OK;
 }
 
+
+static ngx_int_t
+ngx_http_upstream_cache_age(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    if (r->upstream == NULL
+        || r->upstream->cache_status <= NGX_HTTP_CACHE_EXPIRED
+        || r->upstream->cache_status == NGX_HTTP_CACHE_REVALIDATED)
+    {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    v->data = ngx_pnalloc(r->pool, NGX_TIME_T_LEN);
+    if (v->data == NULL) {
+        return NGX_ERROR;
+    }
+
+    v->len = ngx_sprintf(v->data, "%T", ngx_time() - r->cache->date) - v->data;
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+
+    return NGX_OK;
+}
+
 #endif