rolled custom daemon code to better match the way daemons are supposed to work under debian.

1 files changed, 260 insertions, 0 deletions

diff --git a/lib/nickserver/daemon.rb b/lib/nickserver/daemon.rb
new file mode 100644
index 0000000..9eb2ff5
--- /dev/null
+++ b/lib/nickserver/daemon.rb
@@ -0,0 +1,260 @@
+require 'etc'
+require 'fileutils'
+
+#
+# A simple daemon, in a Debian style. Adapted from gem Dante.
+#
+
+module Nickserver
+  class Daemon
+
+    def self.run(&block)
+      self.new.run(&block)
+    end
+
+    def run(&block)
+      parse_options
+      Config.load
+      send("command_#{@command}", &block)
+    end
+
+    private
+
+    MAX_WAIT = 2
+
+    #
+    # PERMISSIONS
+    #
+
+    #
+    # see http://timetobleed.com/5-things-you-dont-know-about-user-ids-that-will-destroy-you/
+    # (hint: it is easy to get it wrong)
+    #
+    def drop_permissions_to(username)
+      if username != 'root'
+        if Process::Sys.getuid == 0
+          Process::Sys.setuid(Etc.getpwnam(username).uid)
+          if root?
+            bail "failed to drop permissions"
+          end
+        else
+          bail "cannot change process uid to #{username}"
+        end
+      end
+    end
+
+    def root?
+      begin
+        Process::Sys.setuid(0)
+      rescue Errno::EPERM
+        false
+      else
+        true
+      end
+    end
+
+    #
+    # PROCESS STUFF
+    #
+
+    def daemonize
+      return bail("Process is already started") if daemon_running?
+      pid = fork do
+        exit if fork
+        Process.setsid
+        exit if fork
+        create_pid_file(Config.pid_file, Config.user)
+        catch_interrupt
+        redirect_output
+        drop_permissions_to(Config.user)
+        File.umask 0000
+        yield
+      end
+
+      if until_true { daemon_running? }
+        puts "Daemon has started successfully"
+        exit(0)
+      else # Failed to start
+        puts "Daemon couldn't be started"
+        exit(1)
+      end
+    end
+
+    def create_pid_file(file, user)
+      File.open file, 'w' do |f|
+        f.write("#{Process.pid}\n")
+      end
+      FileUtils.chown(user, nil, file)
+    rescue Errno::EACCES
+      bail "insufficient permission to create to pid file `#{file}`"
+    rescue Errno::ENOENT
+      bail "bad path for pid file `#{file}`"
+    rescue Errno::EROFS
+      bail "can't create pid file `#{file}` on read-only filesystem"
+    end
+
+    def daemon_running?
+      return false unless File.exist?(Config.pid_file)
+      Process.kill 0, File.read(Config.pid_file).to_i
+      true
+    rescue Errno::ESRCH
+      false
+    end
+
+    def pid_from_file(file)
+      pid = IO.read(file).chomp
+      if pid != ""
+        pid.to_i
+      else
+        nil
+      end
+    end
+
+    def kill_pid
+      file = Config.pid_file
+      if File.exists?(file)
+        pid = pid_from_file(file)
+        if pid
+          Process.kill('TERM', pid)
+          puts "Stopped #{pid}"
+        else
+          bail "Error reading pid file #{file}"
+        end
+        begin
+          FileUtils.rm Config.pid_file
+        rescue Errno::EACCES
+          bail 'insufficient permission to remove pid file'
+        end
+      else
+        bail "could not find pid file #{file}"
+      end
+    rescue => e
+      puts "Failed to stop: #{e}"
+    end
+
+    #
+    # Gracefully handle Ctrl-C
+    #
+    def catch_interrupt
+      Signal.trap("SIGINT") do
+        command_stop
+        $stdout.puts "\nQuit"
+        $stdout.flush
+        exit
+      end
+    end
+
+
+    #
+    # OUTPUT
+    #
+
+    def usage(msg)
+      puts msg
+      puts
+      puts "Usage: nickserver [OPTION] COMMAND"
+      puts "COMMAND is one of: start, stop, restart, status, version"
+      puts "OPTION is one of: --verbose"
+      puts
+      exit 1
+    end
+
+    def bail(msg)
+      puts "Nickserver ERROR: #{msg}."
+      puts "Bailing out."
+      exit(1)
+    end
+
+    #
+    # Redirect output based on log settings (reopens stdout/stderr to specified logfile)
+    # If log_path is nil, redirect to /dev/null to quiet output
+    #
+    def redirect_output
+      if log_path = Config.log_file
+        FileUtils.mkdir_p File.dirname(log_path), :mode => 0755
+        FileUtils.touch log_path
+        File.chmod(0644, log_path)
+        $stdout.reopen(log_path, 'a')
+        $stderr.reopen $stdout
+        $stdout.sync = true
+      else
+        # redirect to /dev/null
+        $stdin.reopen '/dev/null'
+        $stdout.reopen '/dev/null', 'a'
+        $stderr.reopen $stdout
+      end
+    rescue Errno::EACCES
+      bail "no permission to create log file #{log_path}"
+    end
+
+    #
+    # UTILITY
+    #
+
+    #
+    # Runs until the block condition is met or the timeout_seconds is exceeded
+    # until_true(10) { ...return_condition... }
+    #
+    def until_true(timeout_seconds=MAX_WAIT, &block)
+      elapsed_seconds = 0
+      interval = 0.5
+      while elapsed_seconds < timeout_seconds && block.call != true
+        elapsed_seconds += interval
+        sleep(interval)
+      end
+      elapsed_seconds < timeout_seconds
+    end
+
+    def parse_options
+      loop do
+        case ARGV[0]
+          when 'start'     then ARGV.shift; @command = :start
+          when 'stop'      then ARGV.shift; @command = :stop
+          when 'restart'   then ARGV.shift; @command = :restart
+          when 'status'    then ARGV.shift; @command = :status
+          when 'version'   then ARGV.shift; @command = :version
+          when '--verbose' then ARGV.shift; Config.versbose = true
+          when /^-/        then usage("Unknown option: #{ARGV[0].inspect}")
+          else break
+        end
+      end
+      usage("Missing command") unless @command
+    end
+
+    #
+    # COMMANDS
+    #
+
+    def command_version
+      puts "nickserver #{Nickserver::VERSION}, ruby #{RUBY_VERSION}"
+      exit(0)
+    end
+
+    def command_start(&block)
+      daemonize(&block)
+    end
+
+    def command_stop
+      if daemon_running?
+        kill_pid
+        until_true { !daemon_running? }
+      else
+        puts "No processes are running"
+      end
+    end
+
+    def command_restart(&block)
+      command_stop
+      command_start(&block)
+    end
+
+    def command_status
+      if daemon_running?
+        puts "Process id #{pid_from_file(Config.pid_file)}"
+      else
+        puts 'Not running'
+      end
+    end
+
+  end
+end