Background subrequests for cache updates.

Previously, cache background update might not work as expected, making client
wait for it to complete before receiving the final part of a stale response.
This could happen if the response could not be sent to the client socket in one
filter chain call.

Now background cache update is done in a background subrequest.  This type of
subrequest does not block any other subrequests or the main request.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index fcfa2ad94..2a3bb163c 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -879,7 +879,7 @@ ngx_http_upstream_cache(ngx_http_request_t *r, ngx_http_upstream_t *u)
     case NGX_HTTP_CACHE_STALE:
 
         if (((u->conf->cache_use_stale & NGX_HTTP_UPSTREAM_FT_UPDATING)
-             || c->stale_updating) && !r->cache_updater
+             || c->stale_updating) && !r->background
             && u->conf->cache_background_update)
         {
             r->cache->background = 1;
@@ -892,7 +892,7 @@ ngx_http_upstream_cache(ngx_http_request_t *r, ngx_http_upstream_t *u)
     case NGX_HTTP_CACHE_UPDATING:
 
         if (((u->conf->cache_use_stale & NGX_HTTP_UPSTREAM_FT_UPDATING)
-             || c->stale_updating) && !r->cache_updater)
+             || c->stale_updating) && !r->background)
         {
             u->cache_status = rc;
             rc = NGX_OK;
@@ -1076,14 +1076,14 @@ ngx_http_upstream_cache_background_update(ngx_http_request_t *r,
     }
 
     if (ngx_http_subrequest(r, &r->uri, &r->args, &sr, NULL,
-                            NGX_HTTP_SUBREQUEST_CLONE)
+                            NGX_HTTP_SUBREQUEST_CLONE
+                            |NGX_HTTP_SUBREQUEST_BACKGROUND)
         != NGX_OK)
     {
         return NGX_ERROR;
     }
 
     sr->header_only = 1;
-    sr->cache_updater = 1;
 
     return NGX_OK;
 }