diff --git a/Gemfile b/Gemfile
index 11c91e55..0329ec07 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,12 +1,9 @@
 source 'https://rubygems.org'
 
-gem 'activerecord-jdbcpostgresql-adapter', platform: :jruby
 gem 'bcrypt'
 gem 'bootstrap-will_paginate'
 gem 'carrierwave'
 gem 'concurrent-ruby'
-gem 'concurrent-ruby-ext', platform: :ruby
-gem 'activerecord-deprecated_finders', require: 'active_record/deprecated_finders'
 gem 'docker-api', require: 'docker'
 gem 'factory_bot_rails'
 gem 'forgery'
@@ -26,15 +23,11 @@ gem 'rails-i18n'
 gem 'ransack'
 gem 'rubytree'
 gem 'sass-rails', '>= 5.0.7'
-gem 'sdoc', group: :doc
 gem 'slim-rails'
-gem 'bootstrap_pagedown', '>= 1.1.0'
-gem 'pagedown-rails'
+gem 'bootstrap_pagedown'
 gem 'sorcery'
-gem 'thread_safe'
 gem 'turbolinks', '< 5.0.0' # newer versions prevent loading ACE if the page containing is not accessed directly / refreshed
 gem 'uglifier'
-gem 'will_paginate'
 gem 'tubesock'
 gem 'faye-websocket'
 gem 'eventmachine', '1.0.9.1' # explicitly added, this is used by faye-websocket, version 1.2.5 still has an error in eventmachine.rb:202: [BUG] Segmentation fault, which is not yet fixed and causes the whole ruby process to crash
@@ -60,7 +53,6 @@ group :development, :staging do
 end
 
 group :development, :test, :staging do
-  gem 'byebug', platform: :ruby
   gem 'spring'
 end
 
@@ -72,7 +64,6 @@ group :test do
   gem 'codeclimate-test-reporter', require: false
   gem 'database_cleaner'
   gem 'nyan-cat-formatter'
-  gem 'rake'
   gem 'rspec-autotest'
   gem 'rspec-rails'
   gem 'simplecov', require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index 0c196110..b5219e5d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -31,7 +31,6 @@ GEM
       activemodel (= 4.2.10)
       activesupport (= 4.2.10)
       arel (~> 6.0)
-    activerecord-deprecated_finders (1.0.4)
     activesupport (4.2.10)
       i18n (~> 0.7)
       minitest (~> 5.1)
@@ -46,8 +45,8 @@ GEM
     ast (2.4.0)
     autotest-rails (4.2.1)
       ZenTest (~> 4.5)
-    bcrypt (3.1.11)
-    better_errors (2.4.0)
+    bcrypt (3.1.12)
+    better_errors (2.5.0)
       coderay (>= 1.0.0)
       erubi (>= 1.0.0)
       rack (>= 0.9.0)
@@ -60,8 +59,8 @@ GEM
     builder (3.2.3)
     bunny (2.11.0)
       amq-protocol (~> 2.3.0)
-    byebug (10.0.0)
-    capistrano (3.10.1)
+    byebug (10.0.2)
+    capistrano (3.11.0)
       airbrussh (>= 1.0.0)
       i18n
       rake (>= 10.0.0)
@@ -69,7 +68,7 @@ GEM
     capistrano-bundler (1.3.0)
       capistrano (~> 3.1)
       sshkit (~> 1.2)
-    capistrano-rails (1.3.1)
+    capistrano-rails (1.4.0)
       capistrano (~> 3.1)
       capistrano-bundler (~> 1.1)
     capistrano-rvm (0.1.2)
@@ -81,7 +80,7 @@ GEM
       capistrano (~> 3.7)
       capistrano-bundler
       puma (~> 3.4)
-    capybara (3.3.1)
+    capybara (3.7.1)
       addressable
       mini_mime (>= 0.1.3)
       nokogiri (~> 1.8)
@@ -91,7 +90,7 @@ GEM
     capybara-selenium (0.0.6)
       capybara
       selenium-webdriver
-    carrierwave (1.2.2)
+    carrierwave (1.2.3)
       activemodel (>= 4.0.0)
       activesupport (>= 4.0.0)
       mime-types (>= 1.16)
@@ -109,29 +108,27 @@ GEM
       execjs
     coffee-script-source (1.12.2)
     concurrent-ruby (1.0.5)
-    concurrent-ruby-ext (1.0.5)
-      concurrent-ruby (= 1.0.5)
     crass (1.0.4)
     d3-rails (4.13.0)
       railties (>= 3.1)
-    database_cleaner (1.6.2)
+    database_cleaner (1.7.0)
     debug_inspector (0.0.3)
     diff-lcs (1.3)
-    docile (1.1.5)
-    docker-api (1.34.1)
+    docile (1.3.1)
+    docker-api (1.34.2)
       excon (>= 0.47.0)
       multi_json
-    domain_name (0.5.20170404)
+    domain_name (0.5.20180417)
       unf (>= 0.0.5, < 1.0.0)
     erubi (1.7.1)
     erubis (2.7.0)
     eventmachine (1.0.9.1)
-    excon (0.60.0)
+    excon (0.62.0)
     execjs (2.7.0)
-    factory_bot (4.8.2)
+    factory_bot (4.11.1)
       activesupport (>= 3.0.0)
-    factory_bot_rails (4.8.2)
-      factory_bot (~> 4.8.2)
+    factory_bot_rails (4.11.1)
+      factory_bot (~> 4.11.1)
       railties (>= 3.0.0)
     faraday (0.12.2)
       multipart-post (>= 1.2, < 3)
@@ -143,7 +140,7 @@ GEM
     globalid (0.4.1)
       activesupport (>= 4.2.0)
     headless (2.3.1)
-    highline (1.7.10)
+    highline (2.0.0)
     http-cookie (1.0.3)
       domain_name (~> 0.5)
     i18n (0.9.5)
@@ -151,10 +148,11 @@ GEM
     ims-lti (1.1.10)
       builder
       oauth (~> 0.4.5)
+    jaro_winkler (1.5.1)
     jbuilder (2.7.0)
       activesupport (>= 4.2.0)
       multi_json (>= 1.2)
-    jquery-rails (4.3.1)
+    jquery-rails (4.3.3)
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
       thor (>= 0.14, < 2.0)
@@ -163,17 +161,17 @@ GEM
       turbolinks
     json (2.1.0)
     jwt (1.5.6)
-    kramdown (1.16.2)
+    kramdown (1.17.0)
     loofah (2.2.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.0)
       mini_mime (>= 0.1.1)
     method_source (0.9.0)
-    mime-types (3.1)
+    mime-types (3.2.2)
       mime-types-data (~> 3.2015)
-    mime-types-data (3.2016.0521)
-    mini_mime (1.0.0)
+    mime-types-data (3.2018.0812)
+    mini_mime (1.0.1)
     mini_portile2 (2.3.0)
     minitest (5.11.3)
     mnemosyne-ruby (1.5.1)
@@ -184,10 +182,10 @@ GEM
     multipart-post (2.0.0)
     net-scp (1.2.1)
       net-ssh (>= 2.6.5)
-    net-ssh (4.2.0)
+    net-ssh (5.0.2)
     netrc (0.11.0)
-    newrelic_rpm (4.8.0.341)
-    nokogiri (1.8.3)
+    newrelic_rpm (5.3.0.346)
+    nokogiri (1.8.4)
       mini_portile2 (~> 2.3.0)
     nyan-cat-formatter (0.12.0)
       rspec (>= 2.99, >= 2.14.2, < 4)
@@ -198,27 +196,23 @@ GEM
       multi_json (~> 1.3)
       multi_xml (~> 0.5)
       rack (>= 1.2, < 3)
-    pagedown-rails (1.1.4)
-      railties (> 3.1)
     parallel (1.12.1)
-    parser (2.5.0.3)
+    parser (2.5.1.2)
       ast (~> 2.4.0)
     pg (0.21.0)
-    polyamorous (1.3.3)
-      activerecord (>= 3.0)
-    powerpack (0.1.1)
+    powerpack (0.1.2)
     pry (0.11.3)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     pry-byebug (3.6.0)
       byebug (~> 10.0)
       pry (~> 0.10)
-    public_suffix (3.0.2)
-    puma (3.11.3)
-    pundit (1.1.0)
+    public_suffix (3.0.3)
+    puma (3.12.0)
+    pundit (2.0.0)
       activesupport (>= 3.0.0)
     rack (1.6.10)
-    rack-mini-profiler (0.10.7)
+    rack-mini-profiler (1.0.0)
       rack (>= 1.2.0)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -251,58 +245,57 @@ GEM
       thor (>= 0.18.1, < 2.0)
     rainbow (3.0.0)
     rake (12.3.1)
-    ransack (1.8.7)
-      actionpack (>= 3.0)
-      activerecord (>= 3.0)
-      activesupport (>= 3.0)
+    ransack (1.8.9)
+      actionpack (>= 3.0, <= 5.1.1)
+      activerecord (>= 3.0, <= 5.1.1)
+      activesupport (>= 3.0, <= 5.1.1)
       i18n
-      polyamorous (~> 1.3.2)
     rb-fsevent (0.10.3)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
-    rdoc (6.0.1)
     rest-client (2.0.2)
       http-cookie (>= 1.0.2, < 2.0)
       mime-types (>= 1.16, < 4.0)
       netrc (~> 0.8)
-    rspec (3.7.0)
-      rspec-core (~> 3.7.0)
-      rspec-expectations (~> 3.7.0)
-      rspec-mocks (~> 3.7.0)
-    rspec-autotest (1.0.0)
+    rspec (3.8.0)
+      rspec-core (~> 3.8.0)
+      rspec-expectations (~> 3.8.0)
+      rspec-mocks (~> 3.8.0)
+    rspec-autotest (1.0.2)
       rspec-core (>= 2.99.0.beta1, < 4.0.0)
-    rspec-core (3.7.1)
-      rspec-support (~> 3.7.0)
-    rspec-expectations (3.7.0)
+    rspec-core (3.8.0)
+      rspec-support (~> 3.8.0)
+    rspec-expectations (3.8.1)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.7.0)
-    rspec-mocks (3.7.0)
+      rspec-support (~> 3.8.0)
+    rspec-mocks (3.8.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.7.0)
-    rspec-rails (3.7.2)
+      rspec-support (~> 3.8.0)
+    rspec-rails (3.8.0)
       actionpack (>= 3.0)
       activesupport (>= 3.0)
       railties (>= 3.0)
-      rspec-core (~> 3.7.0)
-      rspec-expectations (~> 3.7.0)
-      rspec-mocks (~> 3.7.0)
-      rspec-support (~> 3.7.0)
-    rspec-support (3.7.1)
-    rubocop (0.53.0)
+      rspec-core (~> 3.8.0)
+      rspec-expectations (~> 3.8.0)
+      rspec-mocks (~> 3.8.0)
+      rspec-support (~> 3.8.0)
+    rspec-support (3.8.0)
+    rubocop (0.59.0)
+      jaro_winkler (~> 1.5.1)
       parallel (~> 1.10)
-      parser (>= 2.5)
+      parser (>= 2.5, != 2.5.1.1)
       powerpack (~> 0.1)
       rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
-    rubocop-rspec (1.24.0)
-      rubocop (>= 0.53.0)
-    ruby-progressbar (1.9.0)
+    rubocop-rspec (1.29.1)
+      rubocop (>= 0.58.0)
+    ruby-progressbar (1.10.0)
     rubytree (1.0.0)
       json (~> 2.1)
       structured_warnings (~> 0.3)
-    rubyzip (1.2.1)
-    sass (3.5.6)
+    rubyzip (1.2.2)
+    sass (3.5.7)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
@@ -313,13 +306,11 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
-    sdoc (1.0.0)
-      rdoc (>= 5.0)
-    selenium-webdriver (3.13.0)
+    selenium-webdriver (3.14.0)
       childprocess (~> 0.5)
       rubyzip (~> 1.2)
-    simplecov (0.15.1)
-      docile (~> 1.1.0)
+    simplecov (0.16.1)
+      docile (~> 1.1)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
@@ -330,7 +321,7 @@ GEM
       actionpack (>= 3.1)
       railties (>= 3.1)
       slim (~> 3.0)
-    sorcery (0.11.0)
+    sorcery (0.12.0)
       bcrypt (~> 3.1)
       oauth (~> 0.4, >= 0.4.4)
       oauth2 (~> 1.0, >= 0.8.0)
@@ -343,7 +334,7 @@ GEM
       actionpack (>= 4.0)
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
-    sshkit (1.16.0)
+    sshkit (1.17.0)
       net-scp (>= 1.1.2)
       net-ssh (>= 2.8.0)
     structured_warnings (0.3.0)
@@ -358,17 +349,17 @@ GEM
       coffee-rails
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
-    uglifier (4.1.6)
+    uglifier (4.1.18)
       execjs (>= 0.3.0, < 3)
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.5)
-    unicode-display_width (1.3.0)
+    unicode-display_width (1.4.0)
     web-console (3.3.0)
       activemodel (>= 4.2)
       debug_inspector
       railties (>= 4.2)
-    websocket (1.2.5)
+    websocket (1.2.8)
     websocket-driver (0.7.0)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.3)
@@ -382,15 +373,12 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  activerecord-deprecated_finders
-  activerecord-jdbcpostgresql-adapter
   autotest-rails
   bcrypt
   better_errors
   binding_of_caller
   bootstrap-will_paginate
-  bootstrap_pagedown (>= 1.1.0)
-  byebug
+  bootstrap_pagedown
   capistrano
   capistrano-rails
   capistrano-rvm
@@ -401,7 +389,6 @@ DEPENDENCIES
   carrierwave
   codeclimate-test-reporter
   concurrent-ruby
-  concurrent-ruby-ext
   d3-rails (~> 4.0)
   database_cleaner
   docker-api
@@ -420,7 +407,6 @@ DEPENDENCIES
   newrelic_rpm
   nokogiri
   nyan-cat-formatter
-  pagedown-rails
   pg (< 1.0)
   pry-byebug
   puma
@@ -428,7 +414,6 @@ DEPENDENCIES
   rack-mini-profiler
   rails (= 4.2.10)
   rails-i18n
-  rake
   ransack
   rest-client
   rspec-autotest
@@ -438,18 +423,15 @@ DEPENDENCIES
   rubytree
   rubyzip
   sass-rails (>= 5.0.7)
-  sdoc
   simplecov
   slim-rails
   sorcery
   spring
-  thread_safe
   tubesock
   turbolinks (< 5.0.0)
   uglifier
   web-console
   whenever
-  will_paginate
 
 BUNDLED WITH
-   1.16.1
+   1.16.3
diff --git a/app/assets/javascripts/application.js b/app/assets/javascripts/application.js
index 9ccb9815..22b06a61 100644
--- a/app/assets/javascripts/application.js
+++ b/app/assets/javascripts/application.js
@@ -23,7 +23,4 @@
 //= require_tree ../../../lib
 //= require_tree .
 //= require bootstrap_pagedown
-//= require markdown.converter
-//= require markdown.sanitizer
-//= require markdown.editor
 //= require ace/ext-language_tools
\ No newline at end of file
diff --git a/app/assets/stylesheets/application.css b/app/assets/stylesheets/application.css
index 47163008..e21a40df 100644
--- a/app/assets/stylesheets/application.css
+++ b/app/assets/stylesheets/application.css
@@ -15,5 +15,4 @@
  *= require_tree ../../../vendor/assets/stylesheets/
  *= require_self
  *= require bootstrap_pagedown
- *= require markdown
 */
diff --git a/lib/docker_container_pool.rb b/lib/docker_container_pool.rb
index a2dc1a2e..64cd847c 100644
--- a/lib/docker_container_pool.rb
+++ b/lib/docker_container_pool.rb
@@ -4,9 +4,9 @@ require 'concurrent/timer_task'
 
 class DockerContainerPool
 
-  @containers = ThreadSafe::Hash[ExecutionEnvironment.all.map { |execution_environment| [execution_environment.id, ThreadSafe::Array.new] }]
+  @containers = Concurrent::Hash[ExecutionEnvironment.all.map { |execution_environment| [execution_environment.id, Concurrent::Array.new] }]
   #as containers are not containing containers in use
-  @all_containers = ThreadSafe::Hash[ExecutionEnvironment.all.map { |execution_environment| [execution_environment.id, ThreadSafe::Array.new] }]
+  @all_containers = Concurrent::Hash[ExecutionEnvironment.all.map { |execution_environment| [execution_environment.id, Concurrent::Array.new] }]
 
   def self.clean_up
     Rails.logger.info('Container Pool is now performing a cleanup. ')
diff --git a/spec/lib/docker_container_pool_spec.rb b/spec/lib/docker_container_pool_spec.rb
index 1ff39657..b6f6f42f 100644
--- a/spec/lib/docker_container_pool_spec.rb
+++ b/spec/lib/docker_container_pool_spec.rb
@@ -14,8 +14,8 @@ describe DockerContainerPool do
   end
 
   it 'uses thread-safe data structures' do
-    expect(described_class.instance_variable_get(:@containers)).to be_a(ThreadSafe::Hash)
-    expect(described_class.instance_variable_get(:@containers)[@execution_environment.id]).to be_a(ThreadSafe::Array)
+    expect(described_class.instance_variable_get(:@containers)).to be_a(Concurrent::Hash)
+    expect(described_class.instance_variable_get(:@containers)[@execution_environment.id]).to be_a(Concurrent::Array)
   end
 
   describe '.clean_up' do