Remoting

We’d like to support certain actions from the controller:

• Running arbitrary commands on many machines at once

  • Probably in a shell so you can use regular stuff like cd and &&

  • The inventory knows about SSH host keys and connection addresses, so use that

  • In the future the inventory knows about private network addresses, so make using those optional

• Build the Python package, upload it, and run it

Possibilities:

• Fabric

  • Interestingly it shares some concepts with us, like an inventory with hosts and roles

  • It currently requires TOFU for hosts, lol what https://github.com/fabric/fabric/issues/1804

• Paramiko

  • More flexible

  • No concept of groups or parallelism, have to build that ourselves

  • Can copy files and run shell commands

• Shelling out to ssh and scp

  • Stupid hack, we can write a known_hosts file to a temp location and tell ssh about it

  • No external libraries required

• Mitogen

  • Naturally threaded and async, with easy ability to depend on multiple async calls https://mitogen.networkgenomics.com/getting_started.html#waiting-on-multiple-calls

  • Can run locally-defined Python classes on remote systems

  • No dependencies other than Python and ssh

  • Does unfortunately require a temp known_hosts file as it just shells out to ssh, which also requires this

  • No direct file copy functionality, but I think you can just, read the file locally and write the file remotely, right?

  • I love mitogen

  • It does wayyy more than we need here

  • “ultimately it is not intended for direct use by consumer software”, yes ha ha ha YES

  • Fun????????????

  • Ultimately couldn’t make it work reliably

  • Errors are really hard to debug

Conclusion

We are deploying by shelling out to ssh and scp. We should probably use the same method that we use for deployment for this.