Upstream: different header lists for cached and uncached requests.

The upstream modules remove and alter a number of client headers
before sending the request to upstream.  This set of headers is
smaller or even empty when cache is disabled.

It's still possible that a request in a cache-enabled location is
uncached, for example, if cache entry counter is below min_uses.
In this case it's better to alter a smaller set of headers and
pass more client headers to backend unchanged.  One of the benefits
is enabling server-side byte ranges in such requests.

1 files changed, 33 insertions, 19 deletions

diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index 987e03ee9..91108a8a7 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -55,6 +55,9 @@ typedef struct {
     ngx_array_t                   *body_set;
 
     ngx_http_proxy_headers_t       headers;
+#if (NGX_HTTP_CACHE)
+    ngx_http_proxy_headers_t       headers_cache;
+#endif
     ngx_array_t                   *headers_source;
 
     ngx_array_t                   *proxy_lengths;
@@ -153,7 +156,8 @@ static void *ngx_http_proxy_create_loc_conf(ngx_conf_t *cf);
 static char *ngx_http_proxy_merge_loc_conf(ngx_conf_t *cf,
     void *parent, void *child);
 static ngx_int_t ngx_http_proxy_init_headers(ngx_conf_t *cf,
-    ngx_http_proxy_loc_conf_t *conf, ngx_http_proxy_headers_t *headers);
+    ngx_http_proxy_loc_conf_t *conf, ngx_http_proxy_headers_t *headers,
+    ngx_keyval_t *default_headers);
 
 static char *ngx_http_proxy_pass(ngx_conf_t *cf, ngx_command_t *cmd,
     void *conf);
@@ -1095,7 +1099,11 @@ ngx_http_proxy_create_request(ngx_http_request_t *r)
 
     plcf = ngx_http_get_module_loc_conf(r, ngx_http_proxy_module);
 
+#if (NGX_HTTP_CACHE)
+    headers = u->cacheable ? &plcf->headers_cache : &plcf->headers;
+#else
     headers = &plcf->headers;
+#endif
 
     if (u->method.len) {
         /* HEAD was changed to GET to cache response */
@@ -2515,6 +2523,9 @@ ngx_http_proxy_create_loc_conf(ngx_conf_t *cf)
      *     conf->headers.lengths = NULL;
      *     conf->headers.values = NULL;
      *     conf->headers.hash = { NULL, 0 };
+     *     conf->headers_cache.lengths = NULL;
+     *     conf->headers_cache.values = NULL;
+     *     conf->headers_cache.hash = { NULL, 0 };
      *     conf->body_set_len = NULL;
      *     conf->body_set = NULL;
      *     conf->body_source = { 0, NULL };
@@ -2606,6 +2617,7 @@ ngx_http_proxy_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
 
     u_char                     *p;
     size_t                      size;
+    ngx_int_t                   rc;
     ngx_hash_init_t             hash;
     ngx_http_core_loc_conf_t   *clcf;
     ngx_http_proxy_rewrite_t   *pr;
@@ -3028,26 +3040,37 @@ ngx_http_proxy_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
 
     if (conf->headers_source == NULL) {
         conf->headers = prev->headers;
+#if (NGX_HTTP_CACHE)
+        conf->headers_cache = prev->headers_cache;
+#endif
         conf->headers_source = prev->headers_source;
     }
 
-#if (NGX_HTTP_CACHE)
-    if ((conf->upstream.cache == NULL) != (prev->upstream.cache == NULL)) {
-        conf->headers.hash.buckets = NULL;
+    rc = ngx_http_proxy_init_headers(cf, conf, &conf->headers,
+                                     ngx_http_proxy_headers);
+    if (rc != NGX_OK) {
+        return NGX_CONF_ERROR;
     }
-#endif
 
-    if (ngx_http_proxy_init_headers(cf, conf, &conf->headers) != NGX_OK) {
-        return NGX_CONF_ERROR;
+#if (NGX_HTTP_CACHE)
+
+    if (conf->upstream.cache) {
+        rc = ngx_http_proxy_init_headers(cf, conf, &conf->headers_cache,
+                                         ngx_http_proxy_cache_headers);
+        if (rc != NGX_OK) {
+            return NGX_CONF_ERROR;
+        }
     }
 
+#endif
+
     return NGX_CONF_OK;
 }
 
 
 static ngx_int_t
 ngx_http_proxy_init_headers(ngx_conf_t *cf, ngx_http_proxy_loc_conf_t *conf,
-    ngx_http_proxy_headers_t *headers)
+    ngx_http_proxy_headers_t *headers, ngx_keyval_t *default_headers)
 {
     u_char                       *p;
     size_t                        size;
@@ -3094,17 +3117,6 @@ ngx_http_proxy_init_headers(ngx_conf_t *cf, ngx_http_proxy_loc_conf_t *conf,
         return NGX_ERROR;
     }
 
-
-#if (NGX_HTTP_CACHE)
-
-    h = conf->upstream.cache ? ngx_http_proxy_cache_headers:
-                               ngx_http_proxy_headers;
-#else
-
-    h = ngx_http_proxy_headers;
-
-#endif
-
     src = conf->headers_source->elts;
     for (i = 0; i < conf->headers_source->nelts; i++) {
 
@@ -3116,6 +3128,8 @@ ngx_http_proxy_init_headers(ngx_conf_t *cf, ngx_http_proxy_loc_conf_t *conf,
         *s = src[i];
     }
 
+    h = default_headers;
+
     while (h->key.len) {
 
         src = headers_merged.elts;