Module: OsCtld::ContainerControl::Utils::Runscript::Runner

Included in:
Commands::Exec::Runner, Commands::Runscript::Runner
Defined in:
lib/osctld/container_control/utils/runscript.rb

Constant Summary collapse

TRANSIENT_READY_TIMEOUT = 
30
TRANSIENT_EXIT_TIMEOUT = 
5

Instance Method Summary collapse

Instance Method Details

#osctld_wrapper_callback ⇒ Object

Callback to osctld to relocate self-process from container's wrapper cgroup



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# File 'lib/osctld/container_control/utils/runscript.rb', line 241

def osctld_wrapper_callback
  s = UNIXSocket.new("/run/osctl/user-control/#{Process.uid}.sock")

  payload = {
    cmd: :ct_wrapper_start,
    opts: {
      id: ctid,
      pool:,
      pid: Process.pid
    }
  }

  s.send("#{payload.to_json}\n", 0)

  ret = JSON.parse(s.readline, symbolize_names: true)
  s.close

  return if ret[:status]

  raise "Error during ct_wrapper_start callback: #{ret[:message]}"
end

#runscript_run(opts) ⇒ Object

Execute script in a stopped container

Parameters:

  • opts (Hash)

Options Hash (opts):

  • :script (String) —

    path to the script relative to the rootfs

  • :stdin (IO)
  • :stdout (IO)
  • :stderr (IO)
  • :close_fds (Array<IO>)
  • :wait (Boolean) 


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# File 'lib/osctld/container_control/utils/runscript.rb', line 80

def runscript_run(opts)
  pid = Process.fork do
    Process.setpgrp if opts[:process_group]
    cur_stdin = opts.fetch(:stdin, stdin)
    cur_stdout = opts.fetch(:stdout, stdout)
    cur_stderr = opts.fetch(:stderr, stderr)

    if cur_stdin
      $stdin.reopen(cur_stdin)
    else
      $stdin.close
    end

    $stdout.reopen(cur_stdout)
    $stderr.reopen(cur_stderr) if cur_stderr

    opts[:close_fds] && opts[:close_fds].each(&:close)

    setup_exec_run_env
    osctld_wrapper_callback

    cmd = [
      'lxc-execute',
      '-P', lxc_home,
      '-n', ctid,
      '-o', log_file,
      '-s', "lxc.environment=PATH=#{system_path.join(':')}",
      '-s', 'lxc.environment=HOME=/root',
      '-s', 'lxc.environment=USER=root',
      '--',
      opts[:script]
    ]

    # opts[:cmd] can contain an arbitrary command with multiple arguments
    # and quotes, so the mapping to process arguments is not clear. We use
    # the shell to handle this.
    Process.exec("exec #{cmd.join(' ')}")
  end

  if opts[:wait] === false
    pid
  else
    _, status = Process.wait2(pid)
    wait_for_lxc_stopped
    ok(status.exitstatus)
  end
end

#setup_network ⇒ Object 



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# File 'lib/osctld/container_control/utils/runscript.rb', line 228

def setup_network
  raise 'transient network channel unavailable' unless network_socket

  network_socket.write("ready\n")
  ret = JSON.parse(network_socket.readline, symbolize_names: true)
  ret[:status] ? nil : error(ret[:message])
rescue StandardError => e
  error("network setup failed: #{e.message}")
ensure
  network_socket&.close
end

#stop_transient_runner(pid, graceful: true) ⇒ Object 



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# File 'lib/osctld/container_control/utils/runscript.rb', line 186

def stop_transient_runner(pid, graceful: true)
  grace = graceful ? TRANSIENT_EXIT_TIMEOUT : 0
  deadline = Process.clock_gettime(Process::CLOCK_MONOTONIC) + grace
  loop do
    waited_pid, status = Process.wait2(pid, Process::WNOHANG)
    return status if waited_pid
    break if Process.clock_gettime(Process::CLOCK_MONOTONIC) >= deadline

    sleep(0.05)
  end

  # Stop the payload while its monitor still owns the LXC control
  # socket. Killing the monitor first makes LXC report stopped while
  # lxc-init and its children can survive, orphaned in their namespaces.
  lxc_ct.stop if lxc_ct.running?
  wait_for_process(pid, timeout: TRANSIENT_EXIT_TIMEOUT)
rescue Errno::ECHILD
  nil
end

#wait_transient_ready(io) ⇒ Object 



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# File 'lib/osctld/container_control/utils/runscript.rb', line 206

def wait_transient_ready(io)
  expected = "ready\n"
  received = ''
  deadline = Process.clock_gettime(Process::CLOCK_MONOTONIC) + TRANSIENT_READY_TIMEOUT

  while received.bytesize < expected.bytesize
    remaining = deadline - Process.clock_gettime(Process::CLOCK_MONOTONIC)
    raise Errno::ETIMEDOUT, 'transient init readiness timed out' if remaining <= 0

    chunk = io.read_nonblock(expected.bytesize - received.bytesize, exception: false)
    case chunk
    when :wait_readable
      io.wait_readable(remaining)
    when nil
      raise EOFError, 'transient init closed readiness pipe'
    else
      received << chunk
      raise 'invalid transient init readiness' unless expected.start_with?(received)
    end
  end
end

#with_configured_network(opts) ⇒ Object

Start container with lxc-init, configure network and yield

opts has to contain path to a script that will be executed by lxc-init. The purpose of this script is to keep the container running while the network is being configured and the user command is executed. The script has to write ready\n to standard output, then block on read from standard input and exit.

Parameters:

  • opts (Hash)

Options Hash (opts):

  • :init_script (String) —

    path to the script used to control the container



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# File 'lib/osctld/container_control/utils/runscript.rb', line 139

def with_configured_network(opts)
  ret = nil

  # Pipes for communicating with opts[:init_script]
  in_r, in_w = IO.pipe
  out_r, out_w = IO.pipe

  # Start the container with lxc-init
  runner_pid = runscript_run(
    id: ctid,
    script: opts[:init_script],
    stdin: in_r,
    stdout: out_w,
    stderr: nil,
    close_fds: [in_w, out_r],
    process_group: true,
    wait: false
  )

  in_r.close
  out_w.close

  # Bound startup, not the user's command. Closing these pipes must
  # also happen on EOF, a malformed token or a failed network handshake.
  wait_transient_ready(out_r)
  ct_init_pid = wait_for_lxc_attachable
  ret =
    if ct_init_pid
      setup_network || yield
    else
      error('network setup failed: container is not attachable')
    end
  ret
ensure
  [in_r, in_w, out_r, out_w].compact.each { |io| io.close unless io.closed? }
  begin
    if runner_pid
      # Keep readiness open until cleanup finishes. Early EOF would
      # make the daemon reap this runner before it stops the payload.
      stop_transient_runner(runner_pid, graceful: ret && ret[:status])
      wait_for_lxc_stopped
    end
  ensure
    network_socket&.close unless network_socket&.closed?
  end
end