calculate interests down to connection and parser

by analyzing all of the data down to the parser, one can estimate better
whether io wants to read/write/both, thereby avoiding spurious wakeups.

This also greatly simplifies the monitor API, and solves the 100% CPU
utilization issue.

lib/httpx/connection.rb

@@ -176,9 +176,21 @@ module HTTPX
     end
 
     def interests
-      return :w if @state == :idle
+      # connecting
+      if connecting?
+        return :w unless @io
 
-      :rw
+        return :rw if @io.state == :connected
+
+        return :w
+      end
+
+      # if the write buffer is full, we drain it
+      return :w if @write_buffer.full?
+
+      return @parser.interests if @parser
+
+      nil
     end
 
     def to_io

lib/httpx/connection/http1.rb

@@ -23,6 +23,19 @@ module HTTPX
       @requests = []
     end
 
+    def interests
+      # this means we're processing incoming response already
+      return :r if @request
+
+      return if @requests.empty?
+
+      request = @requests.first
+
+      return :w if request.interests == :w || !@buffer.empty?
+
+      :r
+    end
+
     def reset
       @max_requests = @options.max_requests || MAX_REQUESTS
       @parser.reset!

lib/httpx/connection/http2.rb

@@ -30,6 +30,22 @@ module HTTPX
       init_connection
     end
 
+    def interests
+      return :r if @buffer.full?
+
+      return :w if @connection.state == :closed
+
+      return :r unless (@connection.state == :connected && @handshake_completed)
+
+      return :w unless @pending.empty?
+
+      return :w if @streams.each_key.any? { |r| r.interests == :w }
+
+      return :r if @buffer.empty?
+
+      :rw
+    end
+
     def reset
       init_connection
     end

lib/httpx/extensions.rb

@@ -81,4 +81,4 @@ module HTTPX
       end
     end
   end
-end
+end

lib/httpx/io/tcp.rb

@@ -11,6 +11,8 @@ module HTTPX
 
     attr_reader :addresses
 
+    attr_reader :state
+
     alias_method :host, :ip
 
     def initialize(origin, addresses, options)

lib/httpx/plugins/proxy/http.rb

@@ -7,6 +7,10 @@ module HTTPX
     module Proxy
       module HTTP
         module ConnectionMethods
+          def connecting?
+            super || @state == :connecting || @state == :connected
+          end
+
           private
 
           def transition(nextstate)
@@ -34,7 +38,6 @@ module HTTPX
               when :idle
                 @parser = ProxyParser.new(@write_buffer, @options)
                 set_parser_callbacks(@parser)
-                @parser.on(:close) { transition(:closing) }
               end
             end
             super

lib/httpx/plugins/proxy/socks5.rb

@@ -31,6 +31,10 @@ module HTTPX
             end
           end
 
+          def connecting?
+            super || @state == :authenticating || @state == :negotiating
+          end
+
           private
 
           def transition(nextstate)

lib/httpx/pool.rb

@@ -35,7 +35,6 @@ module HTTPX
 
         @selector.select(timeout) do |monitor|
           monitor.io.call
-          monitor.interests = monitor.io.interests
         end
         @timers.fire
       end
@@ -86,7 +85,7 @@ module HTTPX
       resolver << connection
       return if resolver.empty?
 
-      @_resolver_monitors[resolver] ||= @selector.register(resolver, :w)
+      @_resolver_monitors[resolver] ||= @selector.register(resolver)
     end
 
     def on_resolver_connection(connection)
@@ -128,10 +127,8 @@ module HTTPX
         # if open, an IO was passed upstream, therefore
         # consider it connected already.
         @connected_connections += 1
-        @selector.register(connection, :rw)
-      else
-        @selector.register(connection, :w)
       end
+      @selector.register(connection)
       connection.on(:close) do
         unregister_connection(connection)
       end

lib/httpx/request.rb

@@ -58,6 +58,12 @@ module HTTPX
       @state = :idle
     end
 
+    def interests
+      return :r if @state == :done || @state == :expect
+
+      :w
+    end
+
     # :nocov:
     if RUBY_VERSION < "2.2"
       # rubocop: disable Lint/UriEscapeUnescape:

lib/httpx/selector.rb

@@ -11,21 +11,24 @@ class HTTPX::Selector
   # I/O monitor
   #
   class Monitor
-    attr_accessor :io, :interests, :readiness
+    attr_accessor :io, :readiness
 
-    def initialize(io, interests, reactor)
+    def initialize(io, reactor)
       @io = io
-      @interests = interests
       @reactor = reactor
       @closed = false
     end
 
+    def interests
+      @io.interests
+    end
+
     def readable?
-      READABLE.include?(@interests)
+      READABLE.include?(@io.interests)
     end
 
     def writable?
-      WRITABLE.include?(@interests)
+      WRITABLE.include?(@io.interests)
     end
 
     # closes +@io+, deregisters from reactor (unless +deregister+ is false)
@@ -42,7 +45,7 @@ class HTTPX::Selector
 
     # :nocov:
     def to_s
-      "#<#{self.class}: #{@io}(closed:#{@closed}) #{@interests} #{object_id.to_s(16)}>"
+      "#<#{self.class}: #{@io}(closed:#{@closed}) #{@io.interests} #{object_id.to_s(16)}>"
     end
     # :nocov:
   end
@@ -59,15 +62,14 @@ class HTTPX::Selector
     monitor.close(false) if monitor
   end
 
-  # register +io+ for +interests+ events.
-  def register(io, interests)
+  # register +io+.
+  def register(io)
     monitor = @selectables[io]
-    if monitor
-      monitor.interests = interests
-    else
-      monitor = Monitor.new(io, interests, self)
-      @selectables[io] = monitor
-    end
+    return if monitor
+
+    monitor = Monitor.new(io, self)
+    @selectables[io] = monitor
+
     monitor
   end