commit bfde4f0445def09248cd414d90204f3bdcc32982
author Sergey Kandaurov <pluknet@nginx.com> Tue Oct 10 01:04:54 2017 +0300
committer Sergey Kandaurov <pluknet@nginx.com> Tue Oct 10 01:04:54 2017 +0300
tree 34ef618f47da843c2d3d7dd4a80a55c7e4dfdfb1
parent 607731d594db9955731e56d5f8733bbffcf1c5eb

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.

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 1f6a8fe..2ea521b 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -2404,9 +2404,20 @@
 
             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 @@
         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 @@
 
             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);