I’ve just completed a server move, and the site should be back in business.
The old setup was a beefy server in my basement with 24GB RAM and eight cores. But access was via a jenky IPv6 connection over my cable modem, with external access via a varnish instance running at Digital Ocean. Something in my home network configuration causes that to be extremely unreliable, taking the site offline for days.
It’s now running on an AWS instance, which I hope to make an auto-scaling group. Actual content resides on an EFS volume, which is surprisingly performant. And it’s all behind a new application-style ELB, which also supports HTTPS and HTTP/2.
For now, I am using neither varnish nor a CDN, to see how it goes. Access is directly to the ELB, with every page hitting Apache. WP Super Cache should keep things pretty performant with any luck.
Most normal people will probably never even know this is a thing, but Chrome (and other browsers, really) keeps its own in-memory DNS cache, separate from what the OS keeps. For normal use, this is undoubtedly an improvement.
But every now and then, this can be a burden, and Chrome will have cached something you don’t want it to. For example, you make a change in /etc/hosts to hit a development server bypassing its load balancer or the like, but Chrome has already cached the IP, and thus the hosts change isn’t picked up.
It turns out that you can totally flush this cache—and view its contents. Just pay a visit to chrome://net-internals/#dns and voila! A listing of cache entires, and a “Clear host cache” button. (It also provides a look at how many optimistic DNS queries Chrome performs: many of the entries seem to be unvisited links on sites you’ve visited.)