As we can't control which allocations are destroyed when downscaling a job, we decided
to use Nomad jobs as our runners. Thus for each runner we prewarm for an environment,
a corresponding job is created in Nomad. We create a default job that serves as a template
for the runners. Using this, already existing execution environments can easily be restored,
once Poseidon is restarted.
When running a command interactively, we previously would get stdout
and stderr both served on stdout by Nomad. To circumvent this issue,
we now start a separate execution inside the allocation to split
both streams.
This enables executing commands in runners and forwarding input and
output between the runner and the websocket to the client.
Co-authored-by: Maximilian Paß <maximilian.pass@student.hpi.uni-potsdam.de>
