Hello!

On Wed, Mar 13, 2013 at 12:31:00AM +0800, lanshun zhou wrote:

> in ngx_http_upstream_resolve_handler, posted requests are not handled, so
> if a run time
> dns resolving is failed in a subrequest, (for example, the resolver can not
> be reached, or
> the domain does not exist) the main request will know nothing about this,
> until something
> else attached to this connection happens, like connection broken or a write
> timeout
>
> a patch is attached and hope it helps
>
> simple configuration that can reproduce the problem (with addition module
> enabled):
>
> addition_types *;
>
> resolver your_resolver_here;
>
> location /test {
> set $ihost xxx; # xxx here causes a failed
> run-time dns resolving
> proxy_pass http://$ihost;
> }
>
> location /zzz {
> add_after_body /test;
> return 200 "test";
> }
>
> curl -v http://localhost/zzz

Thank you for your report, see below for comments about the patch.


> diff -ruNp nginx-1.3.14/src/http/ngx_http_upstream.c nginx-1.3.14_zls/src/http/ngx_http_upstream.c
> --- nginx-1.3.14/src/http/ngx_http_upstream.c 2013-02-18 23:08:46.000000000 +0800
> +++ nginx-1.3.14_zls/src/http/ngx_http_upstream.c 2013-03-13 00:01:01.490582380 +0800
> @@ -878,11 +878,13 @@ ngx_http_upstream_cache_send(ngx_http_re
> static void
> ngx_http_upstream_resolve_handler(ngx_resolver_ctx_t *ctx)
> {
> + ngx_connection_t *c;
> ngx_http_request_t *r;
> ngx_http_upstream_t *u;
> ngx_http_upstream_resolved_t *ur;
>
> r = ctx->data;
> + c = r->connection;
>
> u = r->upstream;
> ur = u->resolved;
> @@ -894,7 +896,8 @@ ngx_http_upstream_resolve_handler(ngx_re
> ngx_resolver_strerror(ctx->state));
>
> ngx_http_upstream_finalize_request(r, u, NGX_HTTP_BAD_GATEWAY);
> - return;
> +
> + goto posted_requests;
> }
>
> ur->naddrs = ctx->naddrs;
> @@ -919,13 +922,17 @@ ngx_http_upstream_resolve_handler(ngx_re
> if (ngx_http_upstream_create_round_robin_peer(r, ur) != NGX_OK) {
> ngx_http_upstream_finalize_request(r, u,
> NGX_HTTP_INTERNAL_SERVER_ERROR);
> - return;
> + goto posted_requests;
> }
>
> ngx_resolve_name_done(ctx);
> ur->ctx = NULL;
>
> ngx_http_upstream_connect(r, u);
> +
> +posted_requests:
> +
> + ngx_http_run_posted_requests(c);
> }

Any reason to run posted requests on successful resolution? For
me it looks like something like this should be enough:

--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -894,6 +894,7 @@ ngx_http_upstream_resolve_handler(ngx_re
ngx_resolver_strerror(ctx->state));

ngx_http_upstream_finalize_request(r, u, NGX_HTTP_BAD_GATEWAY);
+ ngx_http_run_posted_requests(r->connection);
return;
}

@@ -919,6 +920,7 @@ ngx_http_upstream_resolve_handler(ngx_re
if (ngx_http_upstream_create_round_robin_peer(r, ur) != NGX_OK) {
ngx_http_upstream_finalize_request(r, u,
NGX_HTTP_INTERNAL_SERVER_ERROR);
+ ngx_http_run_posted_requests(r->connection);
return;
}


--
Maxim Dounin
http://nginx.org/en/donation.html

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