From f5ac727c21d0a588623d351e5293e87e79111763 Mon Sep 17 00:00:00 2001
From: Jamis Buck <jamis@37signals.com>
Date: Sun, 1 Jan 2006 04:11:46 +0000
Subject: [PATCH] Ping each SSH connection every 1s during command processing
 so that long-running commands don't cause the connection to timeout. Add a
 0.01s sleep during the command loop so that the CPU doesn't go ballistic
 while ST is doing its thing.

git-svn-id: http://svn.rubyonrails.org/rails/tools/switchtower@3368 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
---
 CHANGELOG                  |  4 ++++
 lib/switchtower/command.rb | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/CHANGELOG b/CHANGELOG
index 5e211044..3120f30c 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,9 @@
 *SVN*
 
+* Ping each SSH connection every 1s during command processing so that long-running commands don't cause the connection to timeout.
+
+* Add a 0.01s sleep during the command loop so that the CPU doesn't go ballistic while ST is doing its thing.
+
 * Add :restart_via variable for specifying whether restart ought to use :sudo (default, use sudo)
 
 * Use SFTP for file transfers (if available).
diff --git a/lib/switchtower/command.rb b/lib/switchtower/command.rb
index 2ab6d249..6667b4b1 100644
--- a/lib/switchtower/command.rb
+++ b/lib/switchtower/command.rb
@@ -24,6 +24,7 @@ module SwitchTower
     def process!
       logger.debug "processing command"
 
+      since = Time.now
       loop do
         active = 0
         @channels.each do |ch|
@@ -33,6 +34,11 @@ module SwitchTower
         end
 
         break if active == 0
+        if Time.now - since >= 1
+          since = Time.now
+          @channels.each { |ch| ping_connection(ch.connection) }
+        end
+        sleep 0.01 # a brief respite, to keep the CPU from going crazy
       end
 
       logger.trace "command finished"
@@ -46,6 +52,13 @@ module SwitchTower
 
     private
 
+      # send an SSH IGNORE packet (this ought to be added to Net::SSH itself,
+      # so that you could just do connection.ping! instead of the cryptic mess
+      # below...
+      def ping_connection(connection)
+        connection.send_message([2, 4, "ping"].pack("cNA*"))
+      end
+
       def open_channels
         @servers.map do |server|
           @actor.sessions[server].open_channel do |channel|