On Fri, 2024-02-02 at 12:48 +0100, Jiří Setnička via nginx-devel wrote:
> Hello,
>
> Also, I believe that the core of the problem is because of the
> ngx_http_finalize_request(r, NGX_DONE); call in the
> ngx_http_upstream_process_headers function. This call is needed when
> doing an internal redirect after the real upstream request (to close the
> upstream request), but when serving from the cache, there is no upstream
> request to close and this call causes ngx_http_set_lingering_close to be
> called from the ngx_http_finalize_connection with no active request on
> the connection yielding to the segfault.
Hello,
I am Jiří's colleague, and so I have taken a closer look at the problem. Another
indication of the issue is the alert in the error log for non-keepalive
connections,
stating "http request count is zero while closing request."
Upon reviewing the nginx source code, I discovered that the function
ngx_http_upstream_finalize_request(), when called with rc = NGX_DECLINED, does
not invoke
ngx_http_finalize_request(). However, when there is nothing to clean up
(u->cleanup ==
NULL), it does. Therefore, I believe the appropriate fix is to follow the patch
below.
Best, Jan Prachař
# User Jan Prachař <jan.prac...@gmail.com>
# Date 1706877176 -3600
# Fri Feb 02 13:32:56 2024 +0100
# Node ID 851c994b48c48c9cd3d32b9aa402f4821aeb8bb2
# Parent cf3d537ec6706f8713a757df256f2cfccb8f9b01
Upstream: Fix "request count is zero" when procesing X-Accel-Redirect
ngx_http_upstream_finalize_request(r, u, NGX_DECLINED) should not call
ngx_http_finalize_request().
diff -r cf3d537ec670 -r 851c994b48c4 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c Thu Nov 26 21:00:25 2020 +0100
+++ b/src/http/ngx_http_upstream.c Fri Feb 02 13:32:56 2024 +0100
@@ -4340,6 +4340,11 @@
if (u->cleanup == NULL) {
/* the request was already finalized */
+
+ if (rc == NGX_DECLINED) {
+ return;
+ }
+
ngx_http_finalize_request(r, NGX_DONE);
return;
}
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