Module: Bluepill::System

Extended by:
System
Included in:
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
}

Instance Method Summary collapse

Instance Method Details

#can_write_pid_file(pid_file, logger) ⇒ Object 



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# File 'lib/bluepill/system.rb', line 261

def can_write_pid_file(pid_file, logger)
  FileUtils.touch(pid_file)
  File.unlink(pid_file)
  return true

rescue Exception => e
  logger.warning "%s - %s" % [e.class.name, e.message]
  e.backtrace.each {|l| logger.warning l}
  return false
end

#cpu_usage(pid, include_children) ⇒ Object 



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# File 'lib/bluepill/system.rb', line 32

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 { |child_pid|
    cpu_used += ps[child_pid][IDX_MAP[:pcpu]].to_f if ps[child_pid]
  } 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 68

def daemonize(cmd, options = {})
  rd, wr = IO.pipe

  if child = Daemonize.safefork
    # we do not wanna 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

    exit
  end
end

#delete_if_exists(filename) ⇒ Object 



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# File 'lib/bluepill/system.rb', line 114

def delete_if_exists(filename)
  tries = 0

  begin
    File.unlink(filename) if filename && File.exists?(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 242

def drop_privileges(uid, gid, supplementary_groups)
  if ::Process::Sys.geteuid == 0
    uid_num = Etc.getpwnam(uid).uid if uid
    gid_num = Etc.getgrnam(gid).gid if gid

    supplementary_groups ||= []

    group_nums = supplementary_groups.map 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
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 127

def execute_blocking(cmd, options = {})
  rd, wr = IO.pipe

  if child = Daemonize.safefork
    # 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 {
      # 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))
    }

    # 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 58

def get_children(parent_pid)
  child_pids = Array.new
  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.map{|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 42

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 { |child_pid|
    mem_used += ps[child_pid][IDX_MAP[:rss]].to_f if ps[child_pid]
  } if include_children
  mem_used
end

#parse_elapsed_time(str) ⇒ Object 



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# File 'lib/bluepill/system.rb', line 227

def parse_elapsed_time(str)
  # [[dd-]hh:]mm:ss
  if str =~ /(?:(?:(\d+)-)?(\d\d):)?(\d\d):(\d\d)/
    days = ($1 || 0).to_i
    hours = ($2 || 0).to_i
    mins = $3.to_i
    secs = $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 21

def pid_alive?(pid)
  begin
    ::Process.kill(0, pid)
    true
  rescue Errno::EPERM # no permission, but it is definitely alive
    true
  rescue Errno::ESRCH
    false
  end
end

#ps_axu ⇒ Object 



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# File 'lib/bluepill/system.rb', line 211

def ps_axu
  # TODO: need a mutex here
  store[:ps_axu] ||= begin
    # BSD style ps invocation
    lines = `ps axo pid,ppid,pcpu,rss,etime`.split("\n")

    lines.inject(Hash.new) do |mem, line|
      chunks = line.split(/\s+/)
      chunks.delete_if {|c| c.strip.empty? }
      pid = chunks[IDX_MAP[:pid]].strip.to_i
      mem[pid] = chunks
      mem
    end
  end
end

#redirect_io(io_in, io_out, io_err) ⇒ Object 



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# File 'lib/bluepill/system.rb', line 272

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 207

def reset_data
  store.clear unless store.empty?
end

#running_time(pid) ⇒ Object 



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# File 'lib/bluepill/system.rb', line 52

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 203

def store
  @store ||= Hash.new
end