Relocate the service implementation code in to a separate class

Allows for alternative service managers

lib/jetpants.rb

@@ -9,7 +9,7 @@
 module Jetpants; end
 
 $LOAD_PATH.unshift File.join(File.dirname(__FILE__), 'jetpants'), File.join(File.dirname(__FILE__), '..', 'plugins')
-%w(output callback table host db pool topology shard shardpool monkeypatch commandsuite).each {|g| require g}
+%w(output callback table host hostservice db pool topology shard shardpool monkeypatch commandsuite).each {|g| require g}
 
 # Since Jetpants is extremely multi-threaded, we need to force uncaught exceptions to
 # kill all threads in order to have any kind of sane error handling.

lib/jetpants/host.rb

@@ -37,6 +37,7 @@ def initialize(ip)
       @lock = Mutex.new
       @available = nil
       @clone_multi_threaded = false	# default use fast_copy_chain
+      @service_manager = nil
     end
 
     # Returns a Host object for the machine Jetpants is running on.
@@ -770,40 +771,37 @@ def mount_stats(mount)
       end
     end
 
-    ###### Misc methods ########################################################
+    ###### Service management methods ##########################################
+    def service_api
+      if @service_manager.nil?
+        @service_manager = Jetpants::HostService.pick_by_preflight(self)
+      end
+
+      @service_manager
+    end
 
     def service_start(name, options=[])
-      output service(:start, name, options.join(' '))
+      output service_api.start(name, options)
     end
 
     def service_restart(name, options=[])
-      output service(:restart, name, options.join(' '))
+      output service_api.restart(name, options)
     end
 
     def service_stop(name)
-      output service(:stop, name)
+      output service_api.stop(name)
     end
 
     def service_running?(name)
-      status = service(:status, name).downcase
-      # mysql is running if the output of "service mysql status" doesn't include any of these strings
-      not_running_strings = ['not running', 'stop/waiting']
-
-      not_running_strings.none? {|str| status.include? str}
+      service_api.running?(name)
     end
 
-    # Performs the given operation (:start, :stop, :restart, :status) for the
-    # specified service (ie "mysql"). Requires that the "service" bin is in
-    # root's PATH.
-    # Please be aware that the output format and exit codes for the service
-    # binary vary between Linux distros! You may find that you need to override
-    # methods that call Host#service with :status operation (such as
-    # DB#probe_running) in a custom plugin, to parse the output properly on
-    # your chosen Linux distro.
     def service(operation, name, options='')
-      ssh_cmd "service #{name} #{operation.to_s} #{options}".rstrip
+      output "Warning: Calling Host.service directly is deprecated!".red
+      service_manager.service_direct(operation, name, options).rstrip
     end
 
+    ###### Misc methods ########################################################
     # `stat` call to get all the information about the given file
     def get_file_stats(filename)
       mode_re = /^Access:\s+\((?<mode>\d+)\/(?<permissions>[drwx-]+)\)\s+Uid:\s+\(\s+\d+\/\s+(?<user>\w+)\)\s+Gid:\s+\(\s+\d+\/\s+(?<group>\w+)\)$/x

lib/jetpants/hostservice.rb

@@ -0,0 +1,26 @@
+require 'hostservice/upstart'
+
+module Jetpants
+  module HostService
+    def self.pick_by_preflight(host)
+      # We want to pick the first provider which the machine supports. Ruby 1.9.2 has no
+      # `first_where` method like
+      #    [1, 2, 3].first { |i| i > 1 } == 2
+      # but the next line fakes it, by deleting items until we find one which does match, then
+      # taking the first item in the array.
+      # This could be a `.map` or a `.select` but we really don't want to try any more than we
+      # have to.
+      provider = all_providers.drop_while { |candidate| ! candidate.preflight(host) }.first
+      raise "Cannot detect a valid service provider for #{host}" if provider.nil?
+
+      return provider.new(host)
+    end
+
+    def self.all_providers
+      # Service managers that we can support, in order of most to least likely
+      [
+        Jetpants::HostService::Upstart,
+      ]
+    end
+  end
+end

lib/jetpants/hostservice/upstart.rb

@@ -0,0 +1,47 @@
+module Jetpants
+  module HostService
+    class Upstart
+      def self.preflight(host)
+        host.has_installed('service')
+      end
+
+      def initialize(host)
+        @host = host
+      end
+
+      def start(name, options=[])
+        service(:start, name, options.join(' '))
+      end
+
+      def restart(name, options=[])
+        service(:restart, name, options.join(' '))
+      end
+
+      def stop(name)
+        service(:stop, name)
+      end
+
+      def running?(name)
+        status = service(:status, name).downcase
+        # the service is running if the output of "service #{name} status" doesn't include any of
+        # these strings
+        not_running_strings = ['not running', 'stop/waiting']
+
+        not_running_strings.none? {|str| status.include? str}
+      end
+
+      def service_direct(operation, name, options='')
+        service(operation, name, options)
+      end
+
+      # Performs the given operation (:start, :stop, :restart, :status) for the
+      # specified service (ie "mysql"). Requires that the "service" bin is in
+      # root's PATH.
+      # Please be aware that the output format and exit codes for the service
+      # binary vary between Linux distros!
+      def service(operation, name, options='')
+        @host.ssh_cmd "service #{name} #{operation.to_s} #{options}".rstrip
+      end
+    end
+  end
+end