Use keepalive_interval option as IO select timeout

Net::SSH supports sending keepalive packets to the server to check
whether the connection is still alive. For this to work, IO#select needs
to be given a timeout so that the event loop can run periodically and
send the packets.

Author: eugeneius

lib/net/ssh/multi/session.rb

@@ -425,7 +425,7 @@ def loop(wait=nil, &block)
     # +false+ (the block returned +false+).
     def process(wait=nil, &block)
       realize_pending_connections!
-      wait = @connect_threads.any? ? 0 : wait
+      wait = @connect_threads.any? ? 0 : io_select_wait(wait)
 
       return false unless preprocess(&block)
 
@@ -441,6 +441,15 @@ def process(wait=nil, &block)
       end
     end
 
+    def io_select_wait(wait)
+      [wait, keepalive_interval].compact.min
+    end
+
+    def keepalive_interval
+      servers = server_list.select { |s| s.options[:keepalive] }
+      servers.map { |s| s.options[:keepalive_interval] }.compact.min
+    end
+
     # Runs the preprocess stage on all servers. Returns false if the block
     # returns false, and true if there either is no block, or it returns true.
     # This is called as part of the #process method.

test/session_test.rb

@@ -198,4 +198,25 @@ def test_process_should_call_select_on_combined_readers_and_writers_from_all_ser
     IO.expects(:select).with([:a, :b, :c], [:a, :c], nil, 5).returns([[:b, :c], [:a, :c]])
     @session.process(5)
   end
+
+  def test_process_should_pass_minimum_keepalive_interval_as_io_select_timeout
+    @session.use('h1', :keepalive => true)
+    @session.use('h2', :keepalive_interval => 1)
+    @session.use('h3', :keepalive => true, :keepalive_interval => 2)
+    @session.use('h4', :keepalive => true, :keepalive_interval => 3)
+    IO.expects(:select).with([], [], nil, 2)
+    @session.process
+  end
+
+  def test_process_should_pass_wait_as_io_select_timeout_if_provided_and_minimum
+    @session.use('h1', :keepalive => true, :keepalive_interval => 1)
+    IO.expects(:select).with([], [], nil, 1)
+    @session.process(2)
+  end
+
+  def test_process_should_pass_nil_as_io_select_timeout_by_default
+    @session.use('h1')
+    IO.expects(:select).with([], [], nil, nil)
+    @session.process
+  end
 end