Updated patch, with maybe too verbose description. For the record, I did check a few similar modules I'm aware of (nginx-upstream-dynamic-servers, ngx_upstream_jdomain) and haven't found any affected code. So, the effect on third-party modules is hypothetical.
# HG changeset patch # User Aleksei Bavshin <[email protected]> # Date 1654139843 25200 # Wed Jun 01 20:17:23 2022 -0700 # Node ID 488f7a926ba54303c930b0b1e19c2b27e0af5079 # Parent 40926829be83986a3a5a5f941d2014000a0acd2e Resolver: make TCP write timer event cancelable. Similar to 70e65bf8dfd7, the change is made to ensure that the ability to cancel resolver tasks is fully controlled by the caller. As mentioned in the referenced commit, it is safe to make this timer cancelable because resolve tasks can have their own timeouts that are not cancelable. The scenario where this may become a problem is a periodic background resolve task (not tied to a specific request or a client connection), which receives a response with short TTL, large enough to warrant fallback to a TCP query. With each event loop wakeup, we either have a previously set write timer instance or schedule a new one. The non-cancelable write timer can delay or block graceful shutdown of a worker even if the ngx_resolver_ctx_t->cancelable flag is set by the API user, and there are no other tasks or connections. We use the resolver API in this way to maintain the list of upstream server addresses specified with the 'resolve' parameter, and there could be third-party modules implementing similar logic. diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c --- a/src/core/ngx_resolver.c +++ b/src/core/ngx_resolver.c @@ -1389,6 +1389,7 @@ ngx_resolver_send_tcp_query(ngx_resolver rec->tcp->data = rec; rec->tcp->write->handler = ngx_resolver_tcp_write; + rec->tcp->write->cancelable = 1; rec->tcp->read->handler = ngx_resolver_tcp_read; rec->tcp->read->resolver = 1; _______________________________________________ nginx-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
