Use default keepalive interval if none provided

If keepalive is enabled but no interval is provided, we should use the
same default interval as Net::SSH. Currently the keepalive setting is
ignored unless an interval is provided.

Author: eugeneius

lib/net/ssh/multi/session.rb

@@ -122,6 +122,9 @@ module Net; module SSH; module Multi
   class Session
     include SessionActions
 
+    # Default IO.select timeout threshold
+    DEFAULT_IO_SELECT_TIMEOUT = 300
+
     # The Net::SSH::Multi::ServerList managed by this session.
     attr_reader :server_list
 
@@ -447,7 +450,7 @@ def io_select_wait(wait)
 
     def keepalive_interval
       servers = server_list.select { |s| s.options[:keepalive] }
-      servers.map { |s| s.options[:keepalive_interval] }.compact.min
+      servers.map { |s| s.options[:keepalive_interval] || DEFAULT_IO_SELECT_TIMEOUT }.compact.min
     end
 
     # Runs the preprocess stage on all servers. Returns false if the block

test/session_test.rb

@@ -219,4 +219,10 @@ def test_process_should_pass_nil_as_io_select_timeout_by_default
     IO.expects(:select).with([], [], nil, nil)
     @session.process
   end
+
+  def test_process_should_use_default_keepalive_interval_if_none_provided
+    @session.use('h1', :keepalive => true)
+    IO.expects(:select).with([], [], nil, Net::SSH::Multi::Session::DEFAULT_IO_SELECT_TIMEOUT)
+    @session.process
+  end
 end