Node Info Services - Python Async IO and AsyncSSH

A while ago I posted a blog post about a hackathon project I did for work. In this project it required me to run multiple SSH sessions to many machines at once to query the state of the system.

Recently I've been listening to a lot of the Talk Python To Me Podcast, and hearing all about the new async features of Python 3. This got me thinking about this project and how this would be the perfect candidate for some async functionality. Why is this?

Timeouts

So we had a fairly large number of machines that we were wanting to run these SSH Commands on and many of those machines were simply not turned on or currently unavailable for SSH connections. This caused an issue as we simply had to wait for the timeout to occur which was down to about 1 second to ensure we gave enough variance for slow network.

During this 1 second window each of the worked threads were simply waiting there counting down the milliseconds. This was extremely inefficient!

Stateless (Hey it worked out)

So Python introduced the async and await keywords but unfortunately it is likely going to be a while before there are many ORM's that are async capable. This is really handy as I had decided that the API was going to be fairly stateless other than the in memory cache, which means implementing this new approach should be fairly simple.

Approach

So I used Flask for the web framework for the API and there is now a drop in replacement being developed called Quart. This enables the async and await functionality into that same Flask development style that everyone loves with Flask.

​Along with Quart is another python package called asyncSSH which allows the use of async and await for SSH Connections.

So the actual changes required to test out this new approach hopefully shouldn't be too much effort.

The big question is will this actually improve performance?