[nginx] Upstream: fixed tcp_nopush with gRPC.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/ece9b5454b8a
branches:  
changeset: 7307:ece9b5454b8a
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon Jul 02 19:03:04 2018 +0300
description:
Upstream: fixed tcp_nopush with gRPC.

With gRPC it is possible that a request sending is blocked due to flow
control.  Moreover, further sending might be only allowed once the
backend sees all the data we've already sent.  With such a backend
it is required to clear the TCP_NOPUSH socket option to make sure all
the data we've sent are actually delivered to the backend.

As such, we now clear TCP_NOPUSH in ngx_http_upstream_send_request()
also on NGX_AGAIN if c->write->ready is set.  This fixes a test (which
waits for all the 64k bytes as per initial window before allowing more
bytes) with sendfile enabled when the body was written to a file
in a different context.

diffstat:

 src/http/ngx_http_upstream.c |  12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diffs (22 lines):

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
@@ -2012,6 +2012,18 @@ ngx_http_upstream_send_request(ngx_http_
             return;
         }
 
+        if (c->write->ready && c->tcp_nopush == NGX_TCP_NOPUSH_SET) {
+            if (ngx_tcp_push(c->fd) == -1) {
+                ngx_log_error(NGX_LOG_CRIT, c->log, ngx_socket_errno,
+                              ngx_tcp_push_n " failed");
+                ngx_http_upstream_finalize_request(r, u,
+                                               NGX_HTTP_INTERNAL_SERVER_ERROR);
+                return;
+            }
+
+            c->tcp_nopush = NGX_TCP_NOPUSH_UNSET;
+        }
+
         return;
     }