implemented pooling for Docker containers

app/controllers/execution_environments_controller.rb

@@ -25,11 +25,11 @@ class ExecutionEnvironmentsController < ApplicationController
 
   def execute_command
     @docker_client = DockerClient.new(execution_environment: @execution_environment, user: current_user)
-    render(json: @docker_client.execute_command(params[:command]))
+    render(json: @docker_client.execute_arbitrary_command(params[:command]))
   end
 
   def execution_environment_params
-    params[:execution_environment].permit(:docker_image, :exposed_ports, :editor_mode, :file_extension, :help, :indent_size, :name, :permitted_execution_time, :run_command, :test_command, :testing_framework).merge(user_id: current_user.id, user_type: current_user.class.name)
+    params[:execution_environment].permit(:docker_image, :exposed_ports, :editor_mode, :file_extension, :help, :indent_size, :name, :permitted_execution_time, :pool_size, :run_command, :test_command, :testing_framework).merge(user_id: current_user.id, user_type: current_user.class.name)
   end
   private :execution_environment_params
 
@@ -44,6 +44,7 @@ class ExecutionEnvironmentsController < ApplicationController
   end
 
   def set_docker_images
+    DockerClient.check_availability!
     @docker_images = DockerClient.image_tags.sort
   rescue DockerClient::Error => error
     @docker_images = []

app/models/execution_environment.rb

@@ -3,6 +3,8 @@ class ExecutionEnvironment < ActiveRecord::Base
 
   VALIDATION_COMMAND = 'whoami'
 
+  after_initialize :set_default_values
+
   has_many :exercises
   has_many :hints
 
@@ -13,8 +15,15 @@ class ExecutionEnvironment < ActiveRecord::Base
   validates :docker_image, presence: true
   validates :name, presence: true
   validates :permitted_execution_time, numericality: {only_integer: true}, presence: true
+  validates :pool_size, numericality: {only_integer: true}, presence: true
   validates :run_command, presence: true
 
+  def set_default_values
+    self.permitted_execution_time ||= 60
+    self.pool_size ||= 0
+  end
+  private :set_default_values
+
   def to_s
     name
   end
@@ -27,13 +36,13 @@ class ExecutionEnvironment < ActiveRecord::Base
   private :valid_test_setup?
 
   def validate_docker_image?
-    docker_image.present? && Rails.env != 'test'
+    docker_image.present? && !Rails.env.test?
   end
   private :validate_docker_image?
 
   def working_docker_image?
     DockerClient.pull(docker_image) unless DockerClient.image_tags.include?(docker_image)
-    output = DockerClient.new(execution_environment: self).execute_command(VALIDATION_COMMAND)
+    output = DockerClient.new(execution_environment: self).execute_arbitrary_command(VALIDATION_COMMAND)
     errors.add(:docker_image, "error: #{output[:stderr]}") if output[:stderr].present?
   rescue DockerClient::Error => error
     errors.add(:docker_image, "error: #{error}")

app/views/execution_environments/_form.html.slim

@@ -17,6 +17,9 @@
   .form-group
     = f.label(:permitted_execution_time)
     = f.number_field(:permitted_execution_time, class: 'form-control', min: 1)
+  .form-group
+    = f.label(:pool_size)
+    = f.number_field(:pool_size, class: 'form-control', min: 0)
   .form-group
     = f.label(:run_command)
     = f.text_field(:run_command, class: 'form-control', placeholder: 'command %{filename}', required: true)

app/views/execution_environments/show.html.slim

@@ -4,7 +4,7 @@ h1
 
 = row(label: 'execution_environment.name', value: @execution_environment.name)
 = row(label: 'execution_environment.user', value: link_to(@execution_environment.author, @execution_environment.author))
-- [:docker_image, :exposed_ports, :permitted_execution_time, :run_command, :test_command].each do |attribute|
+- [:docker_image, :exposed_ports, :permitted_execution_time, :pool_size, :run_command, :test_command].each do |attribute|
   = row(label: "execution_environment.#{attribute}", value: @execution_environment.send(attribute))
 = row(label: 'execution_environment.testing_framework', value: @testing_framework_adapter.try(:framework_name))
 = row(label: 'execution_environment.help', value: render_markdown(@execution_environment.help))