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module Daemonize
# Try to fork if at all possible retrying every 5 sec if the
# maximum process limit for the system has been reached
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
module_function :safefork
# 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
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
module_function :simulate
# Call a given block as a daemon
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 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
module_function :call_as_daemon
# Transform the current process into a daemon
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 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
module_function :daemonize
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
module_function :close_io
# Free $stdin/$stdout/$stderr file descriptors and
# point them somewhere sensible
def redirect_io(logfile_name)
begin; $stdin.reopen '/dev/null'; rescue ::Exception; end
if logfile_name == 'SYSLOG'
# attempt to use syslog via syslogio
begin
require 'syslogio'
$stdout = ::Daemons::SyslogIO.new($0, :local0, :info, $stdout)
$stderr = ::Daemons::SyslogIO.new($0, :local0, :err, $stderr)
# error out early so we can fallback to null
$stdout.puts "no logfile provided, output redirected to syslog"
rescue ::Exception
# on unsupported platforms simply reopen /dev/null
begin; $stdout.reopen '/dev/null'; rescue ::Exception; end
begin; $stderr.reopen '/dev/null'; rescue ::Exception; end
end
elsif logfile_name
$stdout.reopen logfile_name, 'a'
File.chmod(0644, logfile_name)
$stdout.sync = true
begin; $stderr.reopen $stdout; rescue ::Exception; end
$stderr.sync = true
else
begin; $stdout.reopen '/dev/null'; rescue ::Exception; end
begin; $stderr.reopen '/dev/null'; rescue ::Exception; end
end
end
module_function :redirect_io
end
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