[nginx] gRPC: improved keepalive handling.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/f6047a579ca1
branches:  
changeset: 7349:f6047a579ca1
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Mon Sep 03 19:34:01 2018 +0300
description:
gRPC: improved keepalive handling.

The code is now able to parse additional control frames after
the response is received, and can send control frames as well.
This fixes keepalive problems as observed with grpc-c, which can
send window update and ping frames after the response, see
http://mailman.nginx.org/pipermail/nginx/2018-August/056620.html.

diffstat:

 src/http/modules/ngx_http_grpc_module.c |  100 +++++++++++++++++++++----------
 1 files changed, 67 insertions(+), 33 deletions(-)

diffs (173 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
@@ -111,6 +111,7 @@ typedef struct {
     unsigned                   output_closed:1;
     unsigned                   parsing_headers:1;
     unsigned                   end_stream:1;
+    unsigned                   done:1;
     unsigned                   status:1;
 
     ngx_http_request_t        *request;
@@ -1074,6 +1075,7 @@ ngx_http_grpc_reinit_request(ngx_http_re
     ctx->output_closed = 0;
     ctx->parsing_headers = 0;
     ctx->end_stream = 0;
+    ctx->done = 0;
     ctx->status = 0;
     ctx->connection = NULL;
 
@@ -1093,6 +1095,7 @@ ngx_http_grpc_body_output_filter(void *d
     ngx_int_t               rc;
     ngx_uint_t              next, last;
     ngx_chain_t            *cl, *out, **ll;
+    ngx_http_upstream_t    *u;
     ngx_http_grpc_ctx_t    *ctx;
     ngx_http_grpc_frame_t  *f;
 
@@ -1407,6 +1410,28 @@ ngx_http_grpc_body_output_filter(void *d
         rc = NGX_AGAIN;
     }
 
+    if (ctx->done) {
+
+        /*
+         * We have already got the response and were sending some additional
+         * control frames.  Even if there is still something unsent, stop
+         * here anyway.
+         */
+
+        u = r->upstream;
+        u->length = 0;
+
+        if (ctx->in == NULL
+            && ctx->out == NULL
+            && ctx->output_closed
+            && ctx->state == ngx_http_grpc_st_start)
+        {
+            u->keepalive = 1;
+        }
+
+        ngx_post_event(u->peer.connection->read, &ngx_posted_events);
+    }
+
     return rc;
 }
 
@@ -1832,6 +1857,33 @@ ngx_http_grpc_filter(void *data, ssize_t
             rc = ngx_http_grpc_parse_frame(r, ctx, b);
 
             if (rc == NGX_AGAIN) {
+
+                if (ctx->done) {
+
+                    /*
+                     * We have finished parsing the response and the
+                     * remaining control frames.  If there are unsent
+                     * control frames, post a write event to send them.
+                     */
+
+                    if (ctx->out) {
+                        ngx_post_event(u->peer.connection->write,
+                                       &ngx_posted_events);
+                        return NGX_AGAIN;
+                    }
+
+                    u->length = 0;
+
+                    if (ctx->in == NULL
+                        && ctx->output_closed
+                        && ctx->state == ngx_http_grpc_st_start)
+                    {
+                        u->keepalive = 1;
+                    }
+
+                    break;
+                }
+
                 return NGX_AGAIN;
             }
 
@@ -1898,6 +1950,13 @@ ngx_http_grpc_filter(void *data, ssize_t
                 return NGX_ERROR;
             }
 
+            if (ctx->stream_id && ctx->done) {
+                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                              "upstream sent frame for closed stream %ui",
+                              ctx->stream_id);
+                return NGX_ERROR;
+            }
+
             ctx->padding = 0;
         }
 
@@ -1914,17 +1973,7 @@ ngx_http_grpc_filter(void *data, ssize_t
             ctx->state = ngx_http_grpc_st_start;
 
             if (ctx->flags & NGX_HTTP_V2_END_STREAM_FLAG) {
-                u->length = 0;
-
-                if (ctx->in == NULL
-                    && ctx->out == NULL
-                    && ctx->output_closed
-                    && b->last == b->pos)
-                {
-                    u->keepalive = 1;
-                }
-
-                break;
+                ctx->done = 1;
             }
 
             continue;
@@ -2094,17 +2143,8 @@ ngx_http_grpc_filter(void *data, ssize_t
                                    "grpc trailer done");
 
                     if (ctx->end_stream) {
-                        u->length = 0;
-
-                        if (ctx->in == NULL
-                            && ctx->out == NULL
-                            && ctx->output_closed
-                            && b->last == b->pos)
-                        {
-                            u->keepalive = 1;
-                        }
-
-                        return NGX_OK;
+                        ctx->done = 1;
+                        break;
                     }
 
                     ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
@@ -2121,6 +2161,10 @@ ngx_http_grpc_filter(void *data, ssize_t
                 return NGX_ERROR;
             }
 
+            if (rc == NGX_HTTP_PARSE_HEADER_DONE) {
+                continue;
+            }
+
             /* rc == NGX_AGAIN */
 
             if (ctx->rest == 0) {
@@ -2237,17 +2281,7 @@ ngx_http_grpc_filter(void *data, ssize_t
         ctx->state = ngx_http_grpc_st_start;
 
         if (ctx->flags & NGX_HTTP_V2_END_STREAM_FLAG) {
-            u->length = 0;
-
-            if (ctx->in == NULL
-                && ctx->out == NULL
-                && ctx->output_closed
-                && b->last == b->pos)
-            {
-                u->keepalive = 1;
-            }
-
-            break;
+            ctx->done = 1;
         }
     }