Hi Ben, hope you're doing well.
On Mon, Mar 07, 2022 at 07:53:04PM +0000, Ben Mills wrote: > Greetings nginx, > > nginx version: nginx/1.18.0 running an AWS EC2 instance with an Amazon Linux > 2 AMI. I'd highly recommend to update the nginx OSS to the recent stable version, 1.20.2 [1]. [...] > The nginx service has cached 1.2.3.4 at runtime and the fact that the > https://upstream > now resolves to different IPs has broken the proxy. Restarting the nginx > service > fixes the issue since it then resolves https://upstream to the new ELB IPs. > > Question-1 > > Is there a directive to add to our nginx.conf server block that will force > nginx to > re-resolve its proxy_pass URL upon error? If not upon error, then perhaps at > some > configurable time interval? It's a bit tricky, but it's possible to use the set directive [2] to set up a variable with a backend name for dynamic resolvoing, i.e.: set $backend http://dyn-backned.example.com:8080; proxy_pass $backend; Please note that the resolver directive [3] with a proper nameserver's IP address and a valid parameter is a requirement and needs to be defined as well. > I have my eye on proxy_cache_use_stale, but not sure if this is suited to our > use > case. > > Question-2 > > The devices using this setup are specialized and testing is not easy. Is > there a > command line option that will allow a user with SSH access to the EC2 instance > where nginx is running to verify what nginx currently has in its cache for > https://upstream? (i.e. rather than having to wait for a real device to > error). > The access.log does not display this information, only the error.log does. Sure, it's possible to use find(1) command line utility to walk through a file hierarchy with nginx cache path, please follow the corresponding man page to get more details. References: [1] http://nginx.org/en/linux_packages.html#Amazon-Linux [2] https://nginx.org/en/docs/http/ngx_http_rewrite_module.html#set [3] https://nginx.org/en/docs/http/ngx_http_core_module.html#resolver -- Sergey A. Osokin _______________________________________________ nginx mailing list -- nginx@nginx.org To unsubscribe send an email to nginx-le...@nginx.org
