[nginx] Upstream: fixed error handling of stale and revalidated cache send.

[Sergey Kandaurov]

details:   http://hg.nginx.org/nginx/rev/77fe752b4586
branches:  
changeset: 7126:77fe752b4586
user:      Sergey Kandaurov <pluknet at nginx.com>
date:      Tue Oct 10 01:04:54 2017 +0300
description:
Upstream: fixed error handling of stale and revalidated cache send.

The NGX_DONE value returned from ngx_http_upstream_cache_send() indicates
that upstream was already finalized in ngx_http_upstream_process_headers().
It was treated as a generic error which resulted in duplicate finalization.

Handled NGX_HTTP_UPSTREAM_INVALID_HEADER from ngx_http_upstream_cache_send().
Previously, it could return within ngx_http_upstream_finalize_request(), and
since it's below NGX_HTTP_SPECIAL_RESPONSE, a client connection could stuck.

diffstat:

 src/http/ngx_http_upstream.c |  42 ++++++++++++++++++++++++++++++++++++------
 1 files changed, 36 insertions(+), 6 deletions(-)

diffs (66 lines):

diff -r b8fc701daf8e -r 77fe752b4586 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c	Mon Oct 09 15:59:10 2017 +0300
+++ b/src/http/ngx_http_upstream.c	Tue Oct 10 01:04:54 2017 +0300
@@ -2404,9 +2404,20 @@ ngx_http_upstream_test_next(ngx_http_req
 
             rc = u->reinit_request(r);
 
-            if (rc == NGX_OK) {
-                u->cache_status = NGX_HTTP_CACHE_STALE;
-                rc = ngx_http_upstream_cache_send(r, u);
+            if (rc != NGX_OK) {
+                ngx_http_upstream_finalize_request(r, u, rc);
+                return NGX_OK;
+            }
+
+            u->cache_status = NGX_HTTP_CACHE_STALE;
+            rc = ngx_http_upstream_cache_send(r, u);
+
+            if (rc == NGX_DONE) {
+                return NGX_OK;
+            }
+
+            if (rc == NGX_HTTP_UPSTREAM_INVALID_HEADER) {
+                rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
             }
 
             ngx_http_upstream_finalize_request(r, u, rc);
@@ -2444,6 +2455,14 @@ ngx_http_upstream_test_next(ngx_http_req
         u->cache_status = NGX_HTTP_CACHE_REVALIDATED;
         rc = ngx_http_upstream_cache_send(r, u);
 
+        if (rc == NGX_DONE) {
+            return NGX_OK;
+        }
+
+        if (rc == NGX_HTTP_UPSTREAM_INVALID_HEADER) {
+            rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
+        }
+
         if (valid == 0) {
             valid = r->cache->valid_sec;
             updating = r->cache->updating_sec;
@@ -4150,9 +4169,20 @@ ngx_http_upstream_next(ngx_http_request_
 
             rc = u->reinit_request(r);
 
-            if (rc == NGX_OK) {
-                u->cache_status = NGX_HTTP_CACHE_STALE;
-                rc = ngx_http_upstream_cache_send(r, u);
+            if (rc != NGX_OK) {
+                ngx_http_upstream_finalize_request(r, u, rc);
+                return;
+            }
+
+            u->cache_status = NGX_HTTP_CACHE_STALE;
+            rc = ngx_http_upstream_cache_send(r, u);
+
+            if (rc == NGX_DONE) {
+                return;
+            }
+
+            if (rc == NGX_HTTP_UPSTREAM_INVALID_HEADER) {
+                rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
             }
 
             ngx_http_upstream_finalize_request(r, u, rc);