* The Faye::WebSocket library will "buffer" some output of the connection and emit the `on :message` events in the order of the messages. However, when a ping is sent while the connection has already been closed, it will emit the `on :close` event immediately and drop all other messages (in that "buffer"). This is problematic for very short running executions that generate a long output (as this will be cut off without a proper exit message sent by Poseidon).
* This is the default strategy used when the runner management is disabled. It might be replaced with a generic Docker strategy in the future (without pooling). For now, it allows normal "operation" of CodeOcean without any runner management. However, as no runner system is configured, no command can be executed.
Raising the errors would crash the current thread. As this thread
contains the Eventmachine, that would influence other connections
as well. Attaching the errors to the connection and reading them
after the connection was closed ensures that the thread stays
alive while handling the errors in the main thread of the current
request.
In order to provide an alternative to Poseidon, a strategy for the
DockerContainerPool is added that is used by the runner model.
Co-authored-by: Sebastian Serth <Sebastian.Serth@hpi.de>
Timeouts are now handled correctly and the Runner automatically
creates the execution environment if it could not be found in
Poseidon. The runner is deleted locally if Poseidon returns
a bad request error.
The runner model is only a class responsible for storing information
now. Based on the configuration it picks a strategy for the runner
management. The Poseidon strategy is already implemented and tested.
The Docker strategy will follow.
