Upstream: fixed running posted requests (ticket #788).
Previously, the upstream resolve handler always called
ngx_http_run_posted_requests() to run posted requests after processing the
resolver response. However, if the handler was called directly from the
ngx_resolve_name() function (for example, if the resolver response was cached),
running posted requests from the handler could lead to the following errors:
- If the request was scheduled for termination, it could actually be terminated
in the resolve handler. Upper stack frames could reference the freed request
object in this case.
- If a significant number of requests were posted, and for each of them the
resolve handler was called directly from the ngx_resolve_name() function,
posted requests could be run recursively and lead to stack overflow.
Now ngx_http_run_posted_requests() is only called from asynchronously invoked
resolve handlers.
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 324c59b..8207608 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1143,11 +1143,14 @@
static void
ngx_http_upstream_resolve_handler(ngx_resolver_ctx_t *ctx)
{
+ ngx_uint_t run_posted;
ngx_connection_t *c;
ngx_http_request_t *r;
ngx_http_upstream_t *u;
ngx_http_upstream_resolved_t *ur;
+ run_posted = ctx->async;
+
r = ctx->data;
c = r->connection;
@@ -1211,7 +1214,9 @@
failed:
- ngx_http_run_posted_requests(c);
+ if (run_posted) {
+ ngx_http_run_posted_requests(c);
+ }
}