Reuse runners per user and execution environment

Co-authored-by: Jan-Eric Hellenberg <jan-eric.hellenberg@student.hpi.uni-potsdam.de>
Co-authored-by: Maximilian Pass <maximilian.pass@student.hpi.uni-potsdam.de>

app/models/runner.rb

@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+require 'runner/runner_connection'
+
+class Runner < ApplicationRecord
+  BASE_URL = CodeOcean::Config.new(:code_ocean).read[:runner_management][:url]
+  HEADERS = {'Content-Type' => 'application/json'}.freeze
+  UNUSED_EXPIRATION_TIME = CodeOcean::Config.new(:code_ocean).read[:runner_management][:unused_runner_expiration_time].seconds
+
+  belongs_to :execution_environment
+  belongs_to :user, polymorphic: true
+
+  before_create :get_runner
+  before_destroy :destroy_runner
+
+  validates :execution_environment_id, presence: true
+  validates :user, presence: true
+  validates :time_limit, presence: true
+
+  scope :inactive_runners, -> { where('last_used < ?', Time.now - UNUSED_EXPIRATION_TIME) }
+  
+  def self.for(user, exercise, time_limit = 0)
+    execution_environment = ExecutionEnvironment.find(exercise.execution_environment_id)
+    runner = Runner.find_or_create_by(user: user, execution_environment: execution_environment, time_limit: time_limit)
+
+    return runner if runner.save
+    raise(RunnerNotAvailableError, 'No runner available')
+  end
+
+  def copy_files(files)
+    url = "#{runner_url}/files"
+    body = {files: files.map { |filename, content| {filepath: filename, content: content} }}
+    response = Faraday.patch(url, body.to_json, HEADERS)
+    if response.status == 404
+      # runner has disappeared for some reason
+      self.destroy
+      raise(RunnerNotAvailableError, "Runner unavailable")
+    end
+  end
+
+  def execute_command(command)
+    url = "#{runner_url}/execute"
+    response = Faraday.post(url, {command: command}.to_json, HEADERS)
+    if response.status == 404
+      # runner has disappeared for some reason
+      self.destroy
+      raise(RunnerNotAvailableError, "Runner unavailable")
+    end
+    used_now
+    parse response
+  end
+
+  def execute_interactively(command)
+    starting_time = Time.zone.now
+    websocket_url = execute_command(command)[:websocketUrl]
+    EventMachine.run do
+      socket = RunnerConnection.new(websocket_url)
+      yield(self, socket) if block_given?
+    end
+    Time.zone.now - starting_time # execution time
+  end
+
+  def destroy_runner
+    Faraday.delete runner_url
+  end
+
+  def status
+    # TODO: return actual state retrieved via websocket
+    :timeouted
+  end
+
+  private
+
+  def get_runner
+    url = "#{BASE_URL}/runners"
+    body = {executionEnvironmentId: execution_environment.id}
+    body[:timeLimit] = time_limit
+    response = Faraday.post(url, body.to_json, HEADERS)
+    response_body = parse response
+    self.runner_id = response_body[:runnerId]
+    throw :abort unless response.status == 200
+  end
+
+  def runner_url
+    "#{BASE_URL}/runners/#{runner_id}"
+  end
+
+  def parse(response)
+    JSON.parse(response.body).deep_symbolize_keys
+  end
+
+  def used_now
+    self.last_used = Time.now
+    save
+  end
+end