The author of AutoSpotting here, this is often being asked and I'm happy to clarify it.
The mixed capacity ASGs currently run at decreased capacity when failing to launch spot instances. AutoSpotting will automatically failover to on-demand capacity when spot capacity is lost and back to spot once it can launch it again.
Another useful feature is that it most often requires no configuration of older on-demand ASGs, because it can just take them over and replace their nodes with compatible spot instances.
This makes it very popular for people who run legacy infrastructure that can't be tampered with for whatever reasons, as well as for large-scale rollouts on hundreds of accounts. Someone recently deployed it on infrastructure still running on EC2 Classic started in 2008 or so that wasn't touched for years.
Another large company deployed it with the default opt-in configuration against hundreds of AWS accounts owned by as many teams, many with legacy instances running for years. It would normally take them years to coordinate as a mass migration but it just took them a couple of months to migrate to spot. The teams could opt-in and try it out on their application or opt-out known sensitive workloads. A few weeks later then they centrally switched the configuration to opt-out mode, converting most of their infrastructure to spot literally overnight and saving lots of money with very little configuration effort and very few disruption to the teams.
It's also the most prominent open source tool in this space. Most competition consists of closed-source, commercial (and often quite expensive) tools so if you're currently having any issues or missing functionality, anyone skilled enough can submit a fix or improvement pull request.
It replaces on demand instances in-place. If there’s no spot instances, it will leave them running. If the spot instance gets killed, it will start again as on demand.
It sounds a bit hinky, but it tends to leave you with the number of instances you want running without having to determine what percentage of the ASG should be on demand or spot — especially with the possibility of not being able to start new spot instances if they’ve been terminated.
The mixed capacity ASGs currently run at decreased capacity when failing to launch spot instances. AutoSpotting will automatically failover to on-demand capacity when spot capacity is lost and back to spot once it can launch it again.
Another useful feature is that it most often requires no configuration of older on-demand ASGs, because it can just take them over and replace their nodes with compatible spot instances.
This makes it very popular for people who run legacy infrastructure that can't be tampered with for whatever reasons, as well as for large-scale rollouts on hundreds of accounts. Someone recently deployed it on infrastructure still running on EC2 Classic started in 2008 or so that wasn't touched for years.
Another large company deployed it with the default opt-in configuration against hundreds of AWS accounts owned by as many teams, many with legacy instances running for years. It would normally take them years to coordinate as a mass migration but it just took them a couple of months to migrate to spot. The teams could opt-in and try it out on their application or opt-out known sensitive workloads. A few weeks later then they centrally switched the configuration to opt-out mode, converting most of their infrastructure to spot literally overnight and saving lots of money with very little configuration effort and very few disruption to the teams.
If you want to learn more about it have a look at our FAQ at https://autospotting.org/faq/index.html
It's also the most prominent open source tool in this space. Most competition consists of closed-source, commercial (and often quite expensive) tools so if you're currently having any issues or missing functionality, anyone skilled enough can submit a fix or improvement pull request.