Destroying the runner when Nomad informs us about its allocation being stopped, fixes the error of executions running into their timeout even if the allocation was stopped long ago.
Previously, the execution.Storer interface was embedded in the Runner interface.
However, this resulted in calls like runner.Add(...) to add an execution to the
store which is kind of ugly. Thus, we decided to add only the required functions to
the runner interface and make the execution.Storer a field of the implementation.
When the context passed to Nomad Allocation Exec is cancelled, the
process is not terminated. Instead, just the WebSocket connection is
closed. In order to terminate long-running processes, a special
character is injected into the standard input stream. This character is
parsed by the tty line discipline (tty has to be true). The line
discipline sends a SIGQUIT signal to the process, terminating it and
producing a core dump (in a file called 'core'). The SIGQUIT signal can
be caught but isn't by default, which is why the runner is destroyed if
the program does not terminate during a grace period after the signal
was sent.
We previously didn't really had any structure in our project apart
from creating a new folder for each package in our project root.
Now that we have accumulated some packages, we use the well-known
Golang project layout in order to clearly communicate our intent
with packages. See https://github.com/golang-standards/project-layout
