[nginx] gRPC: disabled keepalive when sending control frames was blocked.

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/dc69f7aa6ca6
branches:  stable-1.14
changeset: 7417:dc69f7aa6ca6
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon Sep 03 19:34:02 2018 +0300
description:
gRPC: disabled keepalive when sending control frames was blocked.

If sending request body was not completed (u->request_body_sent is not set),
the upstream keepalive module won't save such a connection.  However, it
is theoretically possible (though highly unlikely) that sending of some
control frames can be blocked after the request body was sent.  The
ctx->output_blocked flag introduced to disable keepalive in such cases.

diffstat:

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

diffs (57 lines):

diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -112,6 +112,7 @@ typedef struct {
 
     unsigned                   header_sent:1;
     unsigned                   output_closed:1;
+    unsigned                   output_blocked:1;
     unsigned                   parsing_headers:1;
     unsigned                   end_stream:1;
     unsigned                   done:1;
@@ -1076,6 +1077,7 @@ ngx_http_grpc_reinit_request(ngx_http_re
     ctx->state = 0;
     ctx->header_sent = 0;
     ctx->output_closed = 0;
+    ctx->output_blocked = 0;
     ctx->parsing_headers = 0;
     ctx->end_stream = 0;
     ctx->done = 0;
@@ -1413,6 +1415,13 @@ ngx_http_grpc_body_output_filter(void *d
         rc = NGX_AGAIN;
     }
 
+    if (rc == NGX_AGAIN) {
+        ctx->output_blocked = 1;
+
+    } else {
+        ctx->output_blocked = 0;
+    }
+
     if (ctx->done) {
 
         /*
@@ -1427,6 +1436,7 @@ ngx_http_grpc_body_output_filter(void *d
         if (ctx->in == NULL
             && ctx->out == NULL
             && ctx->output_closed
+            && !ctx->output_blocked
             && ctx->state == ngx_http_grpc_st_start)
         {
             u->keepalive = 1;
@@ -1777,6 +1787,7 @@ ngx_http_grpc_process_header(ngx_http_re
                     if (ctx->in == NULL
                         && ctx->out == NULL
                         && ctx->output_closed
+                        && !ctx->output_blocked
                         && b->last == b->pos)
                     {
                         u->keepalive = 1;
@@ -1879,6 +1890,7 @@ ngx_http_grpc_filter(void *data, ssize_t
 
                     if (ctx->in == NULL
                         && ctx->output_closed
+                        && !ctx->output_blocked
                         && ctx->state == ngx_http_grpc_st_start)
                     {
                         u->keepalive = 1;