Re: [PATCH] limit rack version for ruby compatibility

[Eric Wong <e@80x24.org>]

Adam Duke <adamduke@twitter.com> wrote:
> Following up on this, it seems to me like keeping the Ruby 2.2.2
> requirement is the right way to go for rack. If the unicorn project
> wants to continue support for older rubies, the unicorn gemspec should
> be changed to limit the rack dependency to '< 2'. If rack 2.0.0 is
> released and there is no limit on the dependency in unicorn's gemspec,
> it seems to me like any deployments that are not running Ruby 2.2.2
> will fail.

I prefer we drop the rack dependency entirely.  We don't use rack
for much.  This seems doable, (totally untested) patch below:

diff --git a/lib/unicorn.rb b/lib/unicorn.rb
index b0e6bd1..a3eae5e 100644
--- a/lib/unicorn.rb
+++ b/lib/unicorn.rb
@@ -1,9 +1,14 @@
 # -*- encoding: binary -*-
 require 'etc'
 require 'stringio'
-require 'rack'
 require 'kgio'
 
+begin
+  require 'rack'
+rescue LoadError
+  warn 'rack not available, functionality reduced'
+end
+
 # :stopdoc:
 # Unicorn module containing all of the classes (include C extensions) for
 # running a Unicorn web server.  It contains a minimalist HTTP server with just
@@ -32,6 +37,9 @@ module Unicorn
   def self.builder(ru, op)
     # allow Configurator to parse cli switches embedded in the ru file
     op = Unicorn::Configurator::RACKUP.merge!(:file => ru, :optparse => op)
+    if ru =~ /\.ru$/ && !defined?(Rack::Builder)
+      abort "rack and Rack::Builder must be available for processing #{ru}"
+    end
 
     # Op is going to get cleared before the returned lambda is called, so
     # save this value so that it's still there when we need it:
@@ -53,32 +61,33 @@ def self.builder(ru, op)
 
       return inner_app if no_default_middleware
 
+      middleware = { # order matters
+        ContentLength: [],
+        Chunked: [],
+        CommonLogger: [ $stderr ],
+        ShowExceptions: [],
+        Lint: [],
+        TempfileReaper: []
+      }
+
       # return value, matches rackup defaults based on env
       # Unicorn does not support persistent connections, but Rainbows!
       # and Zbatery both do.  Users accustomed to the Rack::Server default
       # middlewares will need ContentLength/Chunked middlewares.
       case ENV["RACK_ENV"]
       when "development"
-        Rack::Builder.new do
-          use Rack::ContentLength
-          use Rack::Chunked
-          use Rack::CommonLogger, $stderr
-          use Rack::ShowExceptions
-          use Rack::Lint
-          use Rack::TempfileReaper if Rack.const_defined?(:TempfileReaper)
-          run inner_app
-        end.to_app
       when "deployment"
-        Rack::Builder.new do
-          use Rack::ContentLength
-          use Rack::Chunked
-          use Rack::CommonLogger, $stderr
-          use Rack::TempfileReaper if Rack.const_defined?(:TempfileReaper)
-          run inner_app
-        end.to_app
+        middleware.delete(:ShowExceptions)
+        middleware.delete(:Lint)
       else
-        inner_app
+        return inner_app
       end
+      Rack::Builder.new do
+        middleware.each do |m, args|
+          use(Rack.const_get(m), *args) if Rack.const_defined?(m)
+        end
+        run inner_app
+      end.to_app
     end
   end
 
diff --git a/lib/unicorn/http_response.rb b/lib/unicorn/http_response.rb
index 7b446c2..ec128e4 100644
--- a/lib/unicorn/http_response.rb
+++ b/lib/unicorn/http_response.rb
@@ -10,10 +10,13 @@
 # is the job of Rack, with the exception of the "Date" and "Status" header.
 module Unicorn::HttpResponse
 
+  STATUS_CODES = defined?(Rack::Utils::HTTP_STATUS_CODES) ?
+                 Rack::Utils::HTTP_STATUS_CODES : {}
+
   # internal API, code will always be common-enough-for-even-old-Rack
   def err_response(code, response_start_sent)
     "#{response_start_sent ? '' : 'HTTP/1.1 '}" \
-      "#{code} #{Rack::Utils::HTTP_STATUS_CODES[code]}\r\n\r\n"
+      "#{code} #{STATUS_CODES[code]}\r\n\r\n"
   end
 
   # writes the rack_response to socket as an HTTP response
@@ -23,7 +26,7 @@ def http_response_write(socket, status, headers, body,
 
     if headers
       code = status.to_i
-      msg = Rack::Utils::HTTP_STATUS_CODES[code]
+      msg = STATUS_CODES[code]
       start = response_start_sent ? ''.freeze : 'HTTP/1.1 '.freeze
       buf = "#{start}#{msg ? %Q(#{code} #{msg}) : status}\r\n" \
             "Date: #{httpdate}\r\n" \
diff --git a/unicorn.gemspec b/unicorn.gemspec
index 2728373..c3f8267 100644
--- a/unicorn.gemspec
+++ b/unicorn.gemspec
@@ -31,11 +31,11 @@
   # version requirements here.
   s.required_ruby_version = '< 3.0'
 
-  # for people that are absolutely stuck on Rails 2.3.2 and can't
-  # up/downgrade to any other version, the Rack dependency may be
-  # commented out.  Nevertheless, upgrading to Rails 2.3.4 or later is
-  # *strongly* recommended for security reasons.
-  s.add_dependency(%q<rack>)
+  # We do not have a hard dependency on rack, it's possible to load
+  # things which respond to #call.  HTTP status lines in responses
+  # won't have descriptive text, only the numeric status.
+  # s.add_dependency(%q<rack>)
+
   s.add_dependency(%q<kgio>, '~> 2.6')
   s.add_dependency(%q<raindrops>, '~> 0.7')

...  Not touching the untested, ancient old_rails stuff, yet