added the ability to limit memory consumption of code submissions executed using Docker

spec/factories/execution_environment.rb

@@ -1,6 +1,7 @@
 FactoryGirl.define do
   factory :coffee_script, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-coffee:latest'
     association :file_type, factory: :dot_coffee
     help
@@ -13,6 +14,7 @@ FactoryGirl.define do
 
   factory :html, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-html:latest'
     association :file_type, factory: :dot_html
     help
@@ -27,6 +29,7 @@ FactoryGirl.define do
 
   factory :java, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-java:latest'
     association :file_type, factory: :dot_java
     help
@@ -41,6 +44,7 @@ FactoryGirl.define do
 
   factory :jruby, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-jruby:latest'
     association :file_type, factory: :dot_rb
     help
@@ -55,6 +59,7 @@ FactoryGirl.define do
 
   factory :node_js, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-node:latest'
     association :file_type, factory: :dot_js
     help
@@ -67,6 +72,7 @@ FactoryGirl.define do
 
   factory :python, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-python:latest'
     association :file_type, factory: :dot_py
     help
@@ -81,6 +87,7 @@ FactoryGirl.define do
 
   factory :ruby, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-ruby:latest'
     association :file_type, factory: :dot_rb
     help
@@ -95,6 +102,7 @@ FactoryGirl.define do
 
   factory :sinatra, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-sinatra:latest'
     association :file_type, factory: :dot_rb
     exposed_ports '4567'
@@ -110,6 +118,7 @@ FactoryGirl.define do
 
   factory :sqlite, class: ExecutionEnvironment do
     created_by_teacher
+    default_memory_limit
     docker_image 'hklement/ubuntu-sqlite:latest'
     association :file_type, factory: :dot_sql
     help
@@ -122,6 +131,10 @@ FactoryGirl.define do
     testing_framework 'SqlResultSetComparatorAdapter'
   end
 
+  trait :default_memory_limit do
+    memory_limit DockerClient::DEFAULT_MEMORY_LIMIT
+  end
+
   trait :help do
     help { Forgery(:lorem_ipsum).words(Forgery(:basic).number(at_least: 50, at_most: 100)) }
   end

spec/lib/docker_client_spec.rb

@@ -25,6 +25,34 @@ describe DockerClient, docker: true do
     end
   end
 
+  describe '.container_creation_options' do
+    let(:container_creation_options) { described_class.container_creation_options(execution_environment) }
+
+    it 'specifies the Docker image' do
+      expect(container_creation_options).to include('Image' => described_class.find_image_by_tag(execution_environment.docker_image).info['RepoTags'].first)
+    end
+
+    it 'specifies the memory limit' do
+      expect(container_creation_options).to include('Memory' => execution_environment.memory_limit.megabytes)
+    end
+
+    it 'specifies to open the standard input stream once' do
+      expect(container_creation_options).to include('OpenStdin' => true, 'StdinOnce' => true)
+    end
+  end
+
+  describe '.container_start_options' do
+    let(:container_start_options) { described_class.container_start_options(execution_environment, '') }
+
+    it 'specifies mapped directories' do
+      expect(container_start_options).to include('Binds' => kind_of(Array))
+    end
+
+    it 'specifies mapped ports' do
+      expect(container_start_options).to include('PortBindings' => kind_of(Hash))
+    end
+  end
+
   describe '.create_container' do
     let(:create_container) { described_class.create_container(execution_environment) }
 
@@ -39,25 +67,25 @@ describe DockerClient, docker: true do
       create_container
     end
 
-    it 'creates a container waiting for input' do
-      expect(Docker::Container).to receive(:create).with('Image' => kind_of(String), 'OpenStdin' => true, 'StdinOnce' => true).and_call_original
+    it 'creates a container' do
+      expect(described_class).to receive(:container_creation_options).with(execution_environment).and_call_original
+      expect(Docker::Container).to receive(:create).with(kind_of(Hash)).and_call_original
       create_container
     end
 
     it 'starts the container' do
-      expect_any_instance_of(Docker::Container).to receive(:start)
+      expect(described_class).to receive(:container_start_options).with(execution_environment, kind_of(String)).and_call_original
+      expect_any_instance_of(Docker::Container).to receive(:start).with(kind_of(Hash)).and_call_original
       create_container
     end
 
     it 'configures mapped directories' do
       expect(described_class).to receive(:mapped_directories).and_call_original
-      expect_any_instance_of(Docker::Container).to receive(:start).with(hash_including('Binds' => kind_of(Array)))
       create_container
     end
 
     it 'configures mapped ports' do
       expect(described_class).to receive(:mapped_ports).with(execution_environment).and_call_original
-      expect_any_instance_of(Docker::Container).to receive(:start).with(hash_including('PortBindings' => kind_of(Hash)))
       create_container
     end
 

spec/models/execution_environment_spec.rb

@@ -13,6 +13,21 @@ describe ExecutionEnvironment do
     expect(execution_environment.errors[:docker_image]).to be_present
   end
 
+  it 'validates the minimum value of the memory limit' do
+    execution_environment.update(memory_limit: DockerClient::MINIMUM_MEMORY_LIMIT / 2)
+    expect(execution_environment.errors[:memory_limit]).to be_present
+  end
+
+  it 'validates the numericality of the memory limit' do
+    execution_environment.update(memory_limit: Math::PI)
+    expect(execution_environment.errors[:memory_limit]).to be_present
+  end
+
+  it 'validates the presence of a memory limit' do
+    execution_environment.update(memory_limit: nil)
+    expect(execution_environment.errors[:memory_limit]).to be_present
+  end
+
   it 'validates the presence of a name' do
     expect(execution_environment.errors[:name]).to be_present
   end