AWS: Add fleet option to use EC2 spot instances

[1ultimat3]

Motivation

EC2 spot instances fit perfectly for most scanning activities. According to AWS up to 90% can be saved in costs.

Approach

The AWS CLI run-instance command in aws-function.sh L321 needs to be adapted according to the official documentation run-instances. By adding the --instance-market-options parameter and providing the configuration file accordingly, spot instances would be used instead of on-demand EC2 instances.

I'd suggest introducing a CLI flag in the fleet configuration to activate the usage of spot instances. The spot instances flag should be disabled by default.

[pdelteil]

It looks interesting. But, what happens if you have 30 instances, running for a couple of days, how are you going to manage the possibility of some instances being dropped? I know it's around 5% of the time, are you willing to test this new feature?

[1ultimat3]

Spot instance interruptions occur and are non-negligible as you mention. I'd follow the "keep it simple stupid" principle here and just provide a warning in case a spot instance has been interrupted - the user should know what he is doing and should implement the interruption handling on his own.

I'd be happy to test the feature.

[pdelteil]

@1ultimat3 You didn't answer my question though.

[1ultimat3]

Sorry, if my answer was not clear.

Question 1: How are you going to manage the possibility of some instances being dropped? Axiom should do absolutely nothing. The user should manage the fleet status and react on changes.

Question 2:I know it's around 5% of the time, are you willing to test this new feature? Yes, I use spot instances for engagements on a regular basis already. I'd be happy to test this new feature once implemented in axiom