Switch IO reactor to nio4r

This moves away from IO.select to using nio4r to allow the reactor to
scale beyond 1024 active clients. This happens when folks are using
websockets usually.

Gemfile

@@ -5,6 +5,7 @@ gemspec
 gem "rdoc"
 gem "rake-compiler"
 
+gem "nio4r", "~> 2.0"
 gem "rack", "< 3.0"
 gem "minitest", "~> 5.11"
 gem "minitest-retry"

lib/puma/reactor.rb

@@ -3,6 +3,8 @@
 require 'puma/util'
 require 'puma/minissl'
 
+require 'nio'
+
 module Puma
   # Internal Docs, Not a public interface.
   #
@@ -49,6 +51,8 @@ module Puma
       @events = server.events
       @app_pool = app_pool
 
+      @selector = NIO::Selector.new
+
       @mutex = Mutex.new
 
       # Read / Write pipes to wake up internal while loop
@@ -57,7 +61,10 @@ module Puma
       @sleep_for = DefaultSleepFor
       @timeouts = []
 
-      @sockets = [@ready]
+      mon = @selector.register(@ready, :r)
+      mon.value = :wakeup
+
+      @sockets = [mon]
     end
 
     private
@@ -122,36 +129,48 @@ module Puma
     # This calculation happens in `calculate_sleep`.
     def run_internal
       sockets = @sockets
+      selector = @selector
 
       while true
         begin
-          ready = IO.select sockets, nil, nil, @sleep_for
+          ready = selector.select @sleep_for
         rescue IOError => e
           Thread.current.purge_interrupt_queue if Thread.current.respond_to? :purge_interrupt_queue
-          if sockets.any? { |socket| socket.closed? }
+          if sockets.any? { |socket| m.value.closed? }
             STDERR.puts "Error in select: #{e.message} (#{e.class})"
             STDERR.puts e.backtrace
-            sockets = sockets.reject { |socket| socket.closed? }
+            sockets = sockets.reject do |socket|
+              if m.value.closed?
+                selector.deregister(socket)
+                true
+              end
+            end
+
             retry
           else
             raise
           end
         end
 
-        if ready and reads = ready[0]
-          reads.each do |c|
-            if c == @ready
+        if ready
+          ready.each do |m|
+            if m.value == :wakeup
               @mutex.synchronize do
                 case @ready.read(1)
                 when "*"
-                  sockets += @input
+                  sockets += @input.map { |i|
+                    mon = selector.register(i, :r)
+                    mon.value = i
+                    mon
+                  }
                   @input.clear
                 when "c"
-                  sockets.delete_if do |s|
-                    if s == @ready
+                  sockets.delete_if do |sm|
+                    if sm.value == :wakeup
                       false
                     else
-                      s.close
+                      sm.value.close
+                      selector.deregister sm
                       true
                     end
                   end
@@ -160,6 +179,8 @@ module Puma
                 end
               end
             else
+              c = m.value
+
               # We have to be sure to remove it from the timeout
               # list or we'll accidentally close the socket when
               # it's in use!
@@ -172,7 +193,8 @@ module Puma
               begin
                 if c.try_to_finish
                   @app_pool << c
-                  sockets.delete c
+                  selector.deregister m
+                  sockets.delete m
                 end
 
               # Don't report these to the lowlevel_error handler, otherwise
@@ -182,7 +204,8 @@ module Puma
                 c.write_500
                 c.close
 
-                sockets.delete c
+                selector.deregister m
+                sockets.delete m
 
               # SSL handshake failure
               rescue MiniSSL::SSLError => e
@@ -193,7 +216,8 @@ module Puma
                 cert = ssl_socket.peercert
 
                 c.close
-                sockets.delete c
+                selector.deregister m
+                sockets.delete m
 
                 @events.ssl_error @server, addr, cert, e
 
@@ -204,7 +228,8 @@ module Puma
                 c.write_400
                 c.close
 
-                sockets.delete c
+                selector.deregister m
+                sockets.delete m
 
                 @events.parse_error @server, c.env, e
               rescue StandardError => e
@@ -213,7 +238,8 @@ module Puma
                 c.write_500
                 c.close
 
-                sockets.delete c
+                selector.deregister m
+                sockets.delete m
               end
             end
           end
@@ -224,10 +250,13 @@ module Puma
             now = Time.now
 
             while @timeouts.first.timeout_at < now
-              c = @timeouts.shift
+              m = @timeouts.shift
+              c = m.value
               c.write_408 if c.in_data_phase
               c.close
-              sockets.delete c
+
+              selector.deregister m
+              sockets.delete m
 
               break if @timeouts.empty?
             end

puma.gemspec

@@ -1,7 +1,5 @@
 # -*- encoding: utf-8 -*-
 
-# This is only used when puma is a git dep from Bundler, keep in sync with Rakefile
-
 version = File.read(File.expand_path("../lib/puma/const.rb", __FILE__))[/VERSION = "(\d+\.\d+\.\d+)"/, 1] || raise
 
 Gem::Specification.new do |s|
@@ -13,6 +11,7 @@ Gem::Specification.new do |s|
   s.email = ["evan@phx.io"]
   s.executables = ["puma", "pumactl"]
   s.extensions = ["ext/puma_http11/extconf.rb"]
+  s.add_runtime_dependency "nio4r", "~> 2.0"
   s.metadata["msys2_mingw_dependencies"] = "openssl"
   s.files = `git ls-files -- bin docs ext lib tools`.split("\n") +
             %w[History.md LICENSE README.md]