Previously, the interactivity timer was implemented in the same file
as the runner. This made the file long and the project structure more
complicated.
Previously, the template job HCL file was hardcoded using go:embed
in the binary. However, this did not allow users running Poseidon
to change its content. Now, users can change the content of the
template job HCL file using the configuration option.
Previously, the server sometimes crashed due to concurrent writes
to the websocket connection. Now, we ensure that only one concurrent
function writes to the websocket at a time by enclosing the WriteMessage
function with a mutex.
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
