Thursday 28 February 2019

Cortana Hosting Off Azure

Yesterday I decided to start moving my skills off Azure. Messaging is still handled by bot service, but the bot lives elsewhere. This is in no way a comment on Azure App Services. It has everything to do with me paying for a GoDaddy VM and I want to have everything in one place. Sure, its not scalable in its current form, but who cares when you have insignificant TPS.

The things that Azure App Services give you for free... a SSL certificate so you can use HTTPS (that you must for bots messaging) and a preconfigured IIS web server that is always managed (because its a container). But its the free tier restrictions... you can't set your web app and skill to "always on", so you get unloaded every 20 minutes. That means your skill will timeout when invoked, and that's a really crappy experience. I wonder how many people actually try a skill twice after it craters the first time? You also can't use web jobs to tickle the endpoint.

So, first step, install Apache. In hindsight, I should have paid GoDaddy the managed fee (that was reasonable, $50 or so) to configure Apache - with their bundled 509 Cert. What a pain... I don't miss running my own web servers.

Why run Apache? Because you want the web server to take care of the SSL for you. It is a lot of work to build a bot supporting HTTPS without a web server. So the trick is, get Apache to handle the secure request, and then tunnel it via proxy to a port without SSL.My node.js bots - they don't know anything about SSL.

How to have all my bots run in one place? Multiple proxies that redirect based on different paths. Instead of https://myserver/api/messages, we now have http://myserver/mybot/api/messages. And the latter redirects to different local ports via a proxy to http://localhost:3000/mybot/api/messages.

Then you have a choice of registering the Cortana skill via a Bot Channel Registration (the right way), or swap out the endpoint after creating a Web App Bot. Why would you want to do the latter? Updated: Because there is a bug in Bot Channel Registrations. Do not use Bot Channel Registration until the glitch is fixed. Create a web app bot, configure the Cortana channel, and then change the bots end point (and tombstone the Azure app service).

I will add my web.conf here when I have time. It is magic that I'll never remember. And the next trick is running node as a daemon. My VM is running Ubuntu server - so
bash -c 'nohup node app &>/dev/null & jobs -p %1'

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