cache gzipped content with proxy_pass

[chrisl]

Maxim,

thank you for your answer. I've patched nginx 0.7.67 to export gzip_ok
to config file variable space (see attachement). I'm not a C guy, but it
seems to work :-) I' currently using it like this:

location /json-data/ {
  set $ae "";
    if ($gzip_ok) {
      set $ae "gzip";
    }
  proxy_pass  http://10.2.3.4/json-upstream/;
  proxy_cache_key         "$gzip_ok:$uri";
  proxy_set_header        User-Agent      "nginx";
  proxy_set_header        Accept-Encoding $ae;
  [ ... ]
}

I get cache keys like this:

# grep -a ^KEY /var/spool/nginx/*
/var/spool/nginx/0c341794ed57bf03d72fb9a207f43d0e:KEY:
:/json-data/123/45/
/var/spool/nginx/17961a45b339647f5e8f239dde713428:KEY:
OK:/json-data/123/45/

By hiding the client User-Agent and Accept-Encoding, I deactivate
upstream gzip detection logic. For this specific task this patch/config
works perfectly. I more general approach would be nice, though.

Chris



--- src/http/ngx_http_variables.c.orig  2010-08-21 12:17:42.000000000
+0200
+++ src/http/ngx_http_variables.c       2010-08-21 12:19:07.000000000
+0200
@@ -66,6 +66,10 @@
     ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t
ngx_http_variable_request_completion(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
+#if (NGX_HTTP_GZIP)
+static ngx_int_t ngx_http_variable_gzip_ok(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
+#endif
 static ngx_int_t ngx_http_variable_request_body(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_http_variable_request_body_file(ngx_http_request_t
*r,
@@ -123,6 +127,9 @@
 #if (NGX_HTTP_GZIP)
     { ngx_string("http_via"), NULL, ngx_http_variable_header,
       offsetof(ngx_http_request_t, headers_in.via), 0, 0 },
+
+    { ngx_string("gzip_ok"), NULL, ngx_http_variable_gzip_ok,
+      0, 0, 0 },
 #endif

 #if (NGX_HTTP_PROXY || NGX_HTTP_REALIP)
@@ -1538,6 +1545,41 @@
     return NGX_OK;
 }

+#if (NGX_HTTP_GZIP)
+static ngx_int_t
+ngx_http_variable_gzip_ok(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    ngx_int_t     rc;
+
+    if (!r->gzip_tested) {
+        rc = ngx_http_gzip_ok(r);
+    
+        if (rc != NGX_OK && rc != NGX_DECLINED) {
+            v->not_found = 1;
+            return NGX_OK;
+        }
+    }
+
+    if (r->gzip_ok) {
+        v->len = 2;
+        v->valid = 1;
+        v->no_cacheable = 0;
+        v->not_found = 0;
+        v->data = (u_char *) "OK";
+
+        return NGX_OK;
+    }
+
+    v->len = 0;
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+    v->data = (u_char *) "";
+
+    return NGX_OK;
+}
+#endif

 static ngx_int_t
 ngx_http_variable_request_body(ngx_http_request_t *r,

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,120314,122064#msg-122064