[nginx] Upstream: p->downstream_error instead of closing connect...

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/35990c69b3ac
branches:  
changeset: 5746:35990c69b3ac
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Fri Jul 04 20:47:16 2014 +0400
description:
Upstream: p->downstream_error instead of closing connection.

Previously, nginx closed client connection in cases when a response body
from upstream was needed to be cached or stored but shouldn't be sent to
the client.  While this is normal for HTTP, it is unacceptable for SPDY.

Fix is to use instead the p->downstream_error flag to prevent nginx from
sending anything downstream.  To make this work, the event pipe code was
modified to properly cache empty responses with the flag set.

diffstat:

 src/event/ngx_event_pipe.c   |  15 +++++----------
 src/http/ngx_http_upstream.c |  20 ++++++++------------
 2 files changed, 13 insertions(+), 22 deletions(-)

diffs (65 lines):

diff --git a/src/event/ngx_event_pipe.c b/src/event/ngx_event_pipe.c
--- a/src/event/ngx_event_pipe.c
+++ b/src/event/ngx_event_pipe.c
@@ -439,7 +439,11 @@ ngx_event_pipe_read_upstream(ngx_event_p
         }
     }
 
-    if (p->cacheable && p->in) {
+    if (p->cacheable && (p->in || p->buf_to_file)) {
+
+        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, p->log, 0,
+                       "pipe write chain");
+
         if (ngx_event_pipe_write_chain_to_temp_file(p) == NGX_ABORT) {
             return NGX_ABORT;
         }
@@ -515,15 +519,6 @@ ngx_event_pipe_write_to_downstream(ngx_e
                 p->in = NULL;
             }
 
-            if (p->cacheable && p->buf_to_file) {
-                ngx_log_debug0(NGX_LOG_DEBUG_EVENT, p->log, 0,
-                               "pipe write chain");
-
-                if (ngx_event_pipe_write_chain_to_temp_file(p) == NGX_ABORT) {
-                    return NGX_ABORT;
-                }
-            }
-
             ngx_log_debug0(NGX_LOG_DEBUG_EVENT, p->log, 0,
                            "pipe write downstream done");
 
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -2357,21 +2357,17 @@ ngx_http_upstream_send_response(ngx_http
 
     if (r->header_only) {
 
-        if (u->cacheable || u->store) {
-
-            if (ngx_shutdown_socket(c->fd, NGX_WRITE_SHUTDOWN) == -1) {
-                ngx_connection_error(c, ngx_socket_errno,
-                                     ngx_shutdown_socket_n " failed");
-            }
-
-            r->read_event_handler = ngx_http_request_empty_handler;
-            r->write_event_handler = ngx_http_request_empty_handler;
-            c->error = 1;
-
-        } else {
+        if (!u->buffering) {
             ngx_http_upstream_finalize_request(r, u, rc);
             return;
         }
+
+        if (!u->cacheable && !u->store) {
+            ngx_http_upstream_finalize_request(r, u, rc);
+            return;
+        }
+
+        u->pipe->downstream_error = 1;
     }
 
     if (r->request_body && r->request_body->temp_file) {