Module: Bluepill::System

Defined in:
lib/bluepill/system.rb

Overview

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

Constant Summary collapse

APPEND_MODE = 
'a'
IDX_MAP =

The position of each field in ps output

{
  pid: 0,
  ppid: 1,
  pcpu: 2,
  rss: 3,
  etime: 4,
  command: 5,
}

Class Method Summary collapse

Class Method Details

.can_write_pid_file(pid_file, logger) ⇒ Object 



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# 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) ⇒ Object 



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# 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) ⇒ Object 



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# 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 = {}) ⇒ Object

Returns the pid of the child that executes the cmd



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# 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) ⇒ Object 



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# 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) ⇒ Object

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



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# 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 = {}) ⇒ Object

Returns the stdout, stderr and exit code of the cmd



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# 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) ⇒ Object 



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# 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) ⇒ Object 



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# 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) ⇒ Object 



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# 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) ⇒ Boolean

Returns:

  • (Boolean) 


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# 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 ⇒ Object 



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# 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) ⇒ Object 



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# 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 ⇒ Object 



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# File 'lib/bluepill/system.rb', line 221

def reset_data
  store.clear unless store.empty?
end

.running_time(pid) ⇒ Object 



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# 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 ⇒ Object 



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# File 'lib/bluepill/system.rb', line 217

def store
  @store ||= {}
end