Call a given block as a daemon
# File lib/daemons/daemonize.rb, line 41 def call_as_daemon(block, logfile_name = nil, app_name = nil) # we use a pipe to return the PID of the daemon rd, wr = IO.pipe if tmppid = safefork # in the parent wr.close pid = rd.read.to_i rd.close Process.waitpid(tmppid) return pid else # in the child rd.close # Detach from the controlling terminal unless sess_id = Process.setsid fail Daemons.RuntimeException.new('cannot detach from controlling terminal') end # Prevent the possibility of acquiring a controlling terminal trap 'SIGHUP', 'IGNORE' exit if pid = safefork wr.write Process.pid wr.close $0 = app_name if app_name # Release old working directory Dir.chdir '/' close_io redirect_io(logfile_name) # Split rand streams between spawning and daemonized process srand block.call exit end end
# File lib/daemons/daemonize.rb, line 121 def close_io # Make sure all input/output streams are closed # Part I: close all IO objects (except for STDIN/STDOUT/STDERR) ObjectSpace.each_object(IO) do |io| unless [STDIN, STDOUT, STDERR].include?(io) io.close rescue nil end end # Make sure all input/output streams are closed # Part II: close all file decriptors (except for STDIN/STDOUT/STDERR) 3.upto(8192) do |i| IO.for_fd(i).close rescue nil end end
Transform the current process into a daemon
# File lib/daemons/daemonize.rb, line 92 def daemonize(logfile_name = nil, app_name = nil) # Fork and exit from the parent safefork && exit # Detach from the controlling terminal unless sess_id = Process.setsid fail Daemons.RuntimeException.new('cannot detach from controlling terminal') end # Prevent the possibility of acquiring a controlling terminal trap 'SIGHUP', 'IGNORE' exit if pid = safefork $0 = app_name if app_name # Release old working directory Dir.chdir '/' close_io redirect_io(logfile_name) # Split rand streams between spawning and daemonized process srand sess_id end
Free STDIN/STDOUT/STDERR file descriptors and point them somewhere sensible
# File lib/daemons/daemonize.rb, line 140 def redirect_io(logfile_name) begin; STDIN.reopen '/dev/null'; rescue ::Exception; end if logfile_name begin STDOUT.reopen logfile_name, 'a' File.chmod(0644, logfile_name) STDOUT.sync = true rescue ::Exception begin; STDOUT.reopen '/dev/null'; rescue ::Exception; end end else begin; STDOUT.reopen '/dev/null'; rescue ::Exception; end end begin; STDERR.reopen STDOUT; rescue ::Exception; end STDERR.sync = true end
Try to fork if at all possible retrying every 5 sec if the maximum process limit for the system has been reached
# File lib/daemons/daemonize.rb, line 4 def safefork tryagain = true while tryagain tryagain = false begin if pid = fork return pid end rescue Errno::EWOULDBLOCK sleep 5 tryagain = true end end end
Simulate the daemonization process (:ontop mode) NOTE: STDOUT and STDERR will not be redirected to the logfile, because in :ontop mode, we normally want to see the output
# File lib/daemons/daemonize.rb, line 24 def simulate(logfile_name = nil, app_name = nil) $0 = app_name if app_name # Release old working directory Dir.chdir '/' close_io # Free STDIN and point it to somewhere sensible begin; STDIN.reopen '/dev/null'; rescue ::Exception; end # Split rand streams between spawning and daemonized process srand end
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