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/controllers/submissions_controller.rb

@@ -152,10 +152,7 @@ class SubmissionsController < ApplicationController
     socket.on :exit do |exit_code|
       EventMachine.stop_event_loop
       status = runner.status
-      if status == :timeouted
-        tubesock.send_data JSON.dump({cmd: :timeout})
-        @output = "timeout: #{@output}"
-      elsif @output.empty?
+      if @output.empty?
         tubesock.send_data JSON.dump({cmd: :write, stream: :stdout, data: "#{t('exercises.implement.no_output', timestamp: l(Time.zone.now, format: :short))}\n"})
       end
       tubesock.send_data JSON.dump({cmd: :write, stream: :stdout, data: "#{t('exercises.implement.exit', exit_code: exit_code)}\n"}) unless status == :timeouted
@@ -168,7 +165,6 @@ class SubmissionsController < ApplicationController
       when :client_kill
         EventMachine.stop_event_loop
         kill_socket(tubesock)
-        runner.destroy
         Rails.logger.debug('Client exited container.')
       when :result
         socket.send event[:data]
@@ -189,11 +185,17 @@ class SubmissionsController < ApplicationController
       if @embed_options[:disable_run]
         kill_socket(tubesock)
       else
+        begin
           @container_execution_time = @submission.run(sanitize_filename) do |runner, socket|
             @waiting_for_container_time = runner.waiting_time
             handle_websockets(tubesock, runner, socket)
           end
           save_run_output
+        rescue RunnerNotAvailableError
+          tubesock.send_data JSON.dump({cmd: :timeout})
+          kill_socket(tubesock)
+          Rails.logger.debug('Runner not available')
+        end
       end
     end
   end

app/errors/application_error.rb

@@ -0,0 +1,2 @@
+class ApplicationError < StandardError
+end

app/errors/runner_not_available_error.rb

@@ -0,0 +1,2 @@
+class RunnerNotAvailableError < ApplicationError
+end

app/jobs/application_job.rb

@@ -0,0 +1,3 @@
+class ApplicationJob < ActiveJob::Base
+  queue_as :default
+end

app/jobs/runner_cleanup_job.rb

@@ -0,0 +1,16 @@
+class RunnerCleanupJob < ApplicationJob
+  CLEANUP_INTERVAL = CodeOcean::Config.new(:code_ocean).read[:runner_management][:cleanup_interval].seconds
+
+  after_perform do |job|
+    # re-schedule job
+    self.class.set(wait: CLEANUP_INTERVAL).perform_later
+  end
+
+  def perform
+    Rails.logger.debug(Time.now)
+    Runner.inactive_runners.each do |runner|
+      Rails.logger.debug("Destroying runner #{runner.runner_id}, unused since #{runner.last_used}")
+      runner.destroy
+    end
+  end
+end

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

app/models/submission.rb

@@ -195,11 +195,10 @@ class Submission < ApplicationRecord
 
   def prepared_runner
     request_time = Time.now
-    runner = Runner.new(execution_environment, execution_environment.permitted_execution_time)
+    runner = Runner.for(user, exercise, execution_environment.permitted_execution_time)
     copy_files_to runner
     runner.waiting_time = Time.now - request_time
     yield(runner) if block_given?
-    runner.destroy
   end
 
   def command_for(template, file)

config/code_ocean.yml.example

@@ -8,6 +8,10 @@ default: &default
     enabled: false
   codeocean_events:
     enabled: false
+  runner_management:
+    url: https://runners.example.org
+    cleanup_interval: 60
+    unused_runner_expiration_time: 180
 
 development:
   flowr:
@@ -21,8 +25,6 @@ development:
     url: https://codeharbor.openhpi.de
   prometheus_exporter:
     enabled: false
-  runner_management:
-    url: https://runners.example.org
 
 production:
   <<: *default

config/initializers/jobs.rb

@@ -0,0 +1 @@
+RunnerCleanupJob.perform_now unless Rake.application.top_level_tasks.to_s.include?('db:')

db/migrate/20210415064948_create_runners.rb

@@ -0,0 +1,14 @@
+class CreateRunners < ActiveRecord::Migration[5.2]
+  def change
+    create_table :runners do |t|
+      t.string :runner_id
+      t.references :execution_environment
+      t.references :user, polymorphic: true
+      t.integer :time_limit
+      t.float :waiting_time
+      t.datetime :last_used
+
+      t.timestamps
+    end
+  end
+end

db/schema.rb

@@ -339,6 +339,20 @@ ActiveRecord::Schema.define(version: 2021_05_12_133612) do
     t.index ["user_id", "user_type", "created_at"], name: "index_rfc_on_user_and_created_at", order: { created_at: :desc }
   end
 
+  create_table "runners", force: :cascade do |t|
+    t.string "runner_id"
+    t.bigint "execution_environment_id"
+    t.string "user_type"
+    t.bigint "user_id"
+    t.integer "time_limit"
+    t.float "waiting_time"
+    t.datetime "last_used"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["execution_environment_id"], name: "index_runners_on_execution_environment_id"
+    t.index ["user_type", "user_id"], name: "index_runners_on_user_type_and_user_id"
+  end
+
   create_table "searches", id: :serial, force: :cascade do |t|
     t.integer "exercise_id", null: false
     t.integer "user_id", null: false

lib/runner/runner.rb

@@ -1,58 +0,0 @@
-# frozen_string_literal: true
-
-class Runner
-  BASE_URL = CodeOcean::Config.new(:code_ocean).read[:runner_management][:url]
-  HEADERS = {'Content-Type' => 'application/json'}.freeze
-
-  attr_accessor :waiting_time
-
-  def initialize(execution_environment, time_limit = nil)
-    url = "#{BASE_URL}/runners"
-    body = {executionEnvironmentId: execution_environment.id}
-    body[:timeLimit] = time_limit if time_limit
-    response = Faraday.post(url, body.to_json, HEADERS)
-    response = parse response
-    @id = response[:runnerId]
-  end
-
-  def copy_files(files)
-    url = "#{runner_url}/files"
-    body = {files: files.map { |filename, content| {filepath: filename, content: content} }}
-    Faraday.patch(url, body.to_json, HEADERS)
-  end
-
-  def execute_command(command)
-    url = "#{runner_url}/execute"
-    response = Faraday.post(url, {command: command}.to_json, HEADERS)
-    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
-    Faraday.delete runner_url
-  end
-
-  def status
-    # TODO: return actual state retrieved via websocket
-    :timeouted
-  end
-
-  private
-
-  def runner_url
-    "#{BASE_URL}/runners/#{@id}"
-  end
-
-  def parse(response)
-    JSON.parse(response.body).deep_symbolize_keys
-  end
-end