Add monkey patch to unicorn to fix eof? problem

Rack with Unicorn is unable to handle chunked requests due to private `eof?` method.
This exposes `eof?` not changing `rack` behavior.

Issue: https://gitlab.com/gitlab-org/gitlab-ee/issues/8539

Gemfile

@@ -7,6 +7,11 @@ gem_versions = {}
 gem_versions['activerecord_sane_schema_dumper'] = rails5? ? '1.0'    : '0.2'
 gem_versions['rails']                           = rails5? ? '5.0.7'  : '4.2.10'
 gem_versions['rails-i18n']                      = rails5? ? '~> 5.1' : '~> 4.0.9'
+
+# The 2.0.6 version of rack requires monkeypatch to be present in
+# `config.ru`. This can be removed once a new update for Rack
+# is available that contains https://github.com/rack/rack/pull/1201.
+gem_versions['rack']                            = rails5? ? '2.0.6' : '1.6.11'
 # --- The end of special code for migrating to Rails 5.0 ---
 
 source 'https://rubygems.org'
@@ -154,6 +159,8 @@ gem 'icalendar'
 gem 'diffy', '~> 3.1.0'
 
 # Application server
+gem 'rack', gem_versions['rack']
+
 group :unicorn do
   gem 'unicorn', '~> 5.1.0'
   gem 'unicorn-worker-killer', '~> 0.4.4'

Gemfile.lock

@@ -1088,6 +1088,7 @@ DEPENDENCIES
   pry-rails (~> 0.3.4)
   puma (~> 3.12)
   puma_worker_killer
+  rack (= 2.0.6)
   rack-attack (~> 4.4.1)
   rack-cors (~> 1.0.0)
   rack-oauth2 (~> 1.2.1)

Gemfile.rails4.lock

@@ -1079,6 +1079,7 @@ DEPENDENCIES
   pry-rails (~> 0.3.4)
   puma (~> 3.12)
   puma_worker_killer
+  rack (= 1.6.11)
   rack-attack (~> 4.4.1)
   rack-cors (~> 1.0.0)
   rack-oauth2 (~> 1.2.1)

changelogs/unreleased/unicorn-monkey-patch.yml

+---
+title: Add monkey patch to unicorn to fix eof? problem
+merge_request: 23385
+author:
+type: fixed

config.ru

@@ -13,6 +13,10 @@ if defined?(Unicorn)
     # Max memory size (RSS) per worker
     use Unicorn::WorkerKiller::Oom, min, max
   end
+
+  # Monkey patch for fixing Rack 2.0.6 bug:
+  # https://gitlab.com/gitlab-org/gitlab-ee/issues/8539
+  Unicorn::StreamInput.send(:public, :eof?) # rubocop:disable GitlabSecurity/PublicSend
 end
 
 require ::File.expand_path('../config/environment',  __FILE__)