Improve robustness during outages

[jooola]

Yesterday, the Hetzner Cloud API had an outage, and it appears that the docker machine driver did not handle it well.

You can see that from 2024-11-13 17:00:00 to 2024-11-14 08:00:00, the amount of requests to /server_types, /images and /locations is unexpectedly high. Also, the amount of requests for single action was also really high.

This leads into rate limits, while waiting for servers to be created.

I see a few possible improvements:

• When waiting for action, use an exponential back off algorithm to spread the requests over time. You can cap the max waiting time to a sensible value. https://pkg.go.dev/github.com/hetznercloud/hcloud-go/v2/hcloud#WithPollOpts https://pkg.go.dev/github.com/hetznercloud/hcloud-go/v2/hcloud#ExponentialBackoffWithOpts
• Use a single API call to wait for multiple related actions, using https://pkg.go.dev/github.com/hetznercloud/hcloud-go/v2/hcloud#ActionClient.WaitFor or https://pkg.go.dev/github.com/hetznercloud/hcloud-go/v2/hcloud#ActionClient.WaitForFunc (note that the Watch* API is deprecated).
• Maybe cache the call the /locations, /server types and /images, those shouldn't change that often. Unless you are checking for a server type availability ?

[JonasProgrammer]

Free stress testing, I don't see the issue.

Bad jokes aside, sorry this caused you headaches. I'll have a look to get the exponential back-off implemented soon. Regarding error handling in general, I am somewhat torn as to what the best approach is. We do have explicit retry with a set timeout, which was implemented as a feature request. The default behaviour is to fail-fast, as it always was, but it could be changed in a major version bump. When using the CLI this would be what I expect, but I do see the issue with some docker-machine RPC talking applications, such as Rancher, going for a request-storm in fail-fast mode.
As for the caching, I do get the point of them being stable. However, I cannot really be sure in which environment the driver is running. Granted, vanilla docker-machine would be useless without a writeable home directory. But given its PRC nature, it could be run with any kinds of restrictions, so long one takes care it can access provided SSH key files.