[nginx] Fixed background requests with asynchronous operations.

[Roman Arutyunyan]

details:   http://hg.nginx.org/nginx/rev/5e05118678af
branches:  
changeset: 7011:5e05118678af
user:      Roman Arutyunyan <arut at nginx.com>
date:      Mon May 29 23:33:38 2017 +0300
description:
Fixed background requests with asynchronous operations.

If the main request was finalized while a background request performed an
asynchronous operation, the main request ended up in ngx_http_writer() and was
not finalized until a network event or a timeout.  For example, cache
background update with aio enabled made nginx unable to process further client
requests or close the connection, keeping it open until client closes it.

Now regular finalization of the main request is not suspended because of an
asynchronous operation in another request.

If a background request was terminated while an asynchronous operation was in
progress, background request's write event handler was changed to
ngx_http_request_finalizer() and never called again.

Now, whenever a request is terminated while an asynchronous operation is in
progress, connection error flag is set to make further finalizations of any
request with this connection lead to termination.

These issues appeared in 1aeaae6e9446 (not yet released).

diffstat:

 src/http/ngx_http_request.c |  8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diffs (32 lines):

diff -r c1524829af3d -r 5e05118678af src/http/ngx_http_request.c
--- a/src/http/ngx_http_request.c	Mon May 29 16:48:30 2017 +0300
+++ b/src/http/ngx_http_request.c	Mon May 29 23:33:38 2017 +0300
@@ -2331,10 +2331,6 @@ ngx_http_finalize_request(ngx_http_reque
             return;
         }
 
-        if (r->main->blocked) {
-            r->write_event_handler = ngx_http_request_finalizer;
-        }
-
         ngx_http_terminate_request(r, rc);
         return;
     }
@@ -2449,7 +2445,7 @@ ngx_http_finalize_request(ngx_http_reque
         return;
     }
 
-    if (r->buffered || c->buffered || r->postponed || r->blocked) {
+    if (r->buffered || c->buffered || r->postponed) {
 
         if (ngx_http_set_write_handler(r) != NGX_OK) {
             ngx_http_terminate_request(r, 0);
@@ -2530,6 +2526,8 @@ ngx_http_terminate_request(ngx_http_requ
     if (mr->write_event_handler) {
 
         if (mr->blocked) {
+            r->connection->error = 1;
+            r->write_event_handler = ngx_http_request_finalizer;
             return;
         }