module Bluepill::System

This class represents the system that bluepill is running on.. It's mainly used to memoize results of running ps auxx etc so that every watch in the every process will not result in a fork

Constants

APPEND_MODE
IDX_MAP

The position of each field in ps output

Public Instance Methods

can_write_pid_file(pid_file, logger) click to toggle source
# File lib/bluepill/system.rb, line 272
def can_write_pid_file(pid_file, logger)
  FileUtils.touch(pid_file)
  File.unlink(pid_file)
  true
rescue => e
  logger.warning(format('%s - %s', e.class.name, e.message))
  e.backtrace.each { |l| logger.warning l }
  false
end
command(pid) click to toggle source
# File lib/bluepill/system.rb, line 59
def command(pid)
  ps = ps_axu
  return unless ps[pid]
  ps[pid][IDX_MAP[:command]]
end
cpu_usage(pid, include_children) click to toggle source
# File lib/bluepill/system.rb, line 33
def cpu_usage(pid, include_children)
  ps = ps_axu
  return unless ps[pid]
  cpu_used = ps[pid][IDX_MAP[:pcpu]].to_f
  get_children(pid).each do |child_pid|
    cpu_used += ps[child_pid][IDX_MAP[:pcpu]].to_f if ps[child_pid]
  end if include_children
  cpu_used
end
daemonize(cmd, options = {}) click to toggle source

Returns the pid of the child that executes the cmd

# File lib/bluepill/system.rb, line 75
def daemonize(cmd, options = {})
  rd, wr = IO.pipe

  child = Daemonize.safefork
  if child
    # we don't want to create zombies, so detach ourselves from the child exit status
    ::Process.detach(child)

    # parent
    wr.close

    daemon_id = rd.read.to_i
    rd.close

    return daemon_id if daemon_id > 0
  else
    # child
    rd.close

    drop_privileges(options[:uid], options[:gid], options[:supplementary_groups])

    # if we cannot write the pid file as the provided user, err out
    exit unless can_write_pid_file(options[:pid_file], options[:logger])

    to_daemonize = lambda do
      # Setting end PWD env emulates bash behavior when dealing with symlinks
      Dir.chdir(ENV['PWD'] = options[:working_dir].to_s) if options[:working_dir]
      options[:environment].each { |key, value| ENV[key.to_s] = value.to_s } if options[:environment]

      redirect_io(*options.values_at(:stdin, :stdout, :stderr))

      ::Kernel.exec(*Shellwords.shellwords(cmd))
      exit
    end

    daemon_id = Daemonize.call_as_daemon(to_daemonize, nil, cmd)

    File.open(options[:pid_file], 'w') { |f| f.write(daemon_id) }

    wr.write daemon_id
    wr.close

    ::Process.exit!(true)
  end
end
delete_if_exists(filename) click to toggle source
# File lib/bluepill/system.rb, line 121
def delete_if_exists(filename)
  tries = 0

  begin
    File.unlink(filename) if filename && File.exist?(filename)
  rescue IOError, Errno::ENOENT
  rescue Errno::EACCES
    retry if (tries += 1) < 3
    $stderr.puts("Warning: permission denied trying to delete #{filename}")
  end
end
drop_privileges(uid, gid, supplementary_groups) click to toggle source

be sure to call this from a fork otherwise it will modify the attributes of the bluepill daemon

# File lib/bluepill/system.rb, line 257
def drop_privileges(uid, gid, supplementary_groups)
  return unless ::Process::Sys.geteuid.zero?
  uid_num = Etc.getpwnam(uid).uid if uid
  gid_num = Etc.getgrnam(gid).gid if gid
  supplementary_groups ||= []
  group_nums = supplementary_groups.collect do |group|
    Etc.getgrnam(group).gid
  end
  ::Process.groups = [gid_num] if gid
  ::Process.groups |= group_nums unless group_nums.empty?
  ::Process::Sys.setgid(gid_num) if gid
  ::Process::Sys.setuid(uid_num) if uid
  ENV['HOME'] = Etc.getpwuid(uid_num).try(:dir) || ENV['HOME'] if uid
end
execute_blocking(cmd, options = {}) click to toggle source

Returns the stdout, stderr and exit code of the cmd

# File lib/bluepill/system.rb, line 134
def execute_blocking(cmd, options = {})
  rd, wr = IO.pipe

  child = Daemonize.safefork
  if child
    # parent
    wr.close

    cmd_status = rd.read
    rd.close

    ::Process.waitpid(child)

    cmd_status.strip != '' ? Marshal.load(cmd_status) : {exit_code: 0, stdout: '', stderr: ''}
  else
    # child
    rd.close

    # create a child in which we can override the stdin, stdout and stderr
    cmd_out_read, cmd_out_write = IO.pipe
    cmd_err_read, cmd_err_write = IO.pipe

    pid = fork do
      begin
        # grandchild
        drop_privileges(options[:uid], options[:gid], options[:supplementary_groups])

        Dir.chdir(ENV['PWD'] = options[:working_dir].to_s) if options[:working_dir]
        options[:environment].each { |key, value| ENV[key.to_s] = value.to_s } if options[:environment]

        # close unused fds so ancestors wont hang. This line is the only reason we are not
        # using something like popen3. If this fd is not closed, the .read call on the parent
        # will never return because "wr" would still be open in the "exec"-ed cmd
        wr.close

        # we do not care about stdin of cmd
        STDIN.reopen('/dev/null')

        # point stdout of cmd to somewhere we can read
        cmd_out_read.close
        STDOUT.reopen(cmd_out_write)
        cmd_out_write.close

        # same thing for stderr
        cmd_err_read.close
        STDERR.reopen(cmd_err_write)
        cmd_err_write.close

        # finally, replace grandchild with cmd
        ::Kernel.exec(*Shellwords.shellwords(cmd))
      rescue => e
        (cmd_err_write.closed? ? STDERR : cmd_err_write).puts "Exception in grandchild: #{e}."
        (cmd_err_write.closed? ? STDERR : cmd_err_write).puts e.backtrace
        exit 1
      end
    end

    # we do not use these ends of the pipes in the child
    cmd_out_write.close
    cmd_err_write.close

    # wait for the cmd to finish executing and acknowledge it's death
    ::Process.waitpid(pid)

    # collect stdout, stderr and exitcode
    result = {
      stdout: cmd_out_read.read,
      stderr: cmd_err_read.read,
      exit_code: $?.exitstatus,
    }

    # We're done with these ends of the pipes as well
    cmd_out_read.close
    cmd_err_read.close

    # Time to tell the parent about what went down
    wr.write Marshal.dump(result)
    wr.close

    ::Process.exit!
  end
end
get_children(parent_pid) click to toggle source
# File lib/bluepill/system.rb, line 65
def get_children(parent_pid)
  child_pids = []
  ps_axu.each_pair do |_pid, chunks|
    child_pids << chunks[IDX_MAP[:pid]].to_i if chunks[IDX_MAP[:ppid]].to_i == parent_pid.to_i
  end
  grand_children = child_pids.collect { |pid| get_children(pid) }.flatten
  child_pids.concat grand_children
end
memory_usage(pid, include_children) click to toggle source
# File lib/bluepill/system.rb, line 43
def memory_usage(pid, include_children)
  ps = ps_axu
  return unless ps[pid]
  mem_used = ps[pid][IDX_MAP[:rss]].to_f
  get_children(pid).each do |child_pid|
    mem_used += ps[child_pid][IDX_MAP[:rss]].to_f if ps[child_pid]
  end if include_children
  mem_used
end
parse_elapsed_time(str) click to toggle source
# File lib/bluepill/system.rb, line 242
def parse_elapsed_time(str)
  # [[dd-]hh:]mm:ss
  if str =~ /(?:(?:(\d+)-)?(\d\d):)?(\d\d):(\d\d)/
    days = (Regexp.last_match[1] || 0).to_i
    hours = (Regexp.last_match[2] || 0).to_i
    mins = Regexp.last_match[3].to_i
    secs = Regexp.last_match[4].to_i
    ((days * 24 + hours) * 60 + mins) * 60 + secs
  else
    0
  end
end
pid_alive?(pid) click to toggle source
# File lib/bluepill/system.rb, line 22
def pid_alive?(pid)
  ::Process.kill(0, pid)
  true
rescue Errno::EPERM # no permission, but it is definitely alive
  true
rescue Errno::ESRCH
  false
rescue
  false # other falsy (no pid)
end
ps_axu() click to toggle source
# File lib/bluepill/system.rb, line 225
def ps_axu
  # TODO: need a mutex here
  store[:ps_axu] ||= begin
    # BSD style ps invocation
    lines = `ps axo pid,ppid,pcpu,rss,etime,command`.split("\n")

    lines.each_with_object({}) do |line, mem|
      chunks = line.split(/\s+/)
      chunks.delete_if { |c| c.strip.empty? }
      pid = chunks[IDX_MAP[:pid]].strip.to_i
      command = chunks.slice!(IDX_MAP[:command], chunks.length).join ' '
      chunks[IDX_MAP[:command]] = command
      mem[pid] = chunks.flatten
    end
  end
end
redirect_io(io_in, io_out, io_err) click to toggle source
# File lib/bluepill/system.rb, line 282
def redirect_io(io_in, io_out, io_err)
  $stdin.reopen(io_in) if io_in

  if !io_out.nil? && !io_err.nil? && io_out == io_err
    $stdout.reopen(io_out, APPEND_MODE)
    $stderr.reopen($stdout)

  else
    $stdout.reopen(io_out, APPEND_MODE) if io_out
    $stderr.reopen(io_err, APPEND_MODE) if io_err
  end
end
reset_data() click to toggle source
# File lib/bluepill/system.rb, line 221
def reset_data
  store.clear unless store.empty?
end
running_time(pid) click to toggle source
# File lib/bluepill/system.rb, line 53
def running_time(pid)
  ps = ps_axu
  return unless ps[pid]
  parse_elapsed_time(ps[pid][IDX_MAP[:etime]])
end
store() click to toggle source
# File lib/bluepill/system.rb, line 217
def store
  @store ||= {}
end