[Bug 1834875] Re: cloud-init growpart race with udev

[Scott Moser]

If there is a race, or a need to wait, it almost certainly is in cloud-
utils (growpart).  If you use growpart to grow a partition, the result
should be that that is done, and it is ready.  The caller should not
expect that they have to know additional information (to call 'udevadm
settle') or should have to wait some amount of time.

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Title:
  cloud-init growpart race with udev

Status in cloud-init:
  Incomplete
Status in cloud-utils:
  New
Status in systemd package in Ubuntu:
  New

Bug description:
  On Azure, it happens regularly (20-30%), that cloud-init's growpart
  module fails to extend the partition to full size.

  Such as in this example:

  ========================================

  2019-06-28 12:24:18,666 - util.py[DEBUG]: Running command ['growpart', '--dry-run', '/dev/sda', '1'] with allowed return codes [0] (shell=False, capture=True)
  2019-06-28 12:24:19,157 - util.py[DEBUG]: Running command ['growpart', '/dev/sda', '1'] with allowed return codes [0] (shell=False, capture=True)
  2019-06-28 12:24:19,726 - util.py[DEBUG]: resize_devices took 1.075 seconds
  2019-06-28 12:24:19,726 - handlers.py[DEBUG]: finish: init-network/config-growpart: FAIL: running config-growpart with frequency always
  2019-06-28 12:24:19,727 - util.py[WARNING]: Running module growpart (<module 'cloudinit.config.cc_growpart' from '/usr/lib/python3/dist-packages/cloudinit/config/cc_growpart.py'>) failed
  2019-06-28 12:24:19,727 - util.py[DEBUG]: Running module growpart (<module 'cloudinit.config.cc_growpart' from '/usr/lib/python3/dist-packages/cloudinit/config/cc_growpart.py'>) failed
  Traceback (most recent call last):
    File "/usr/lib/python3/dist-packages/cloudinit/stages.py", line 812, in _run_modules
      freq=freq)
    File "/usr/lib/python3/dist-packages/cloudinit/cloud.py", line 54, in run
      return self._runners.run(name, functor, args, freq, clear_on_fail)
    File "/usr/lib/python3/dist-packages/cloudinit/helpers.py", line 187, in run
      results = functor(*args)
    File "/usr/lib/python3/dist-packages/cloudinit/config/cc_growpart.py", line 351, in handle
      func=resize_devices, args=(resizer, devices))
    File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 2521, in log_time
      ret = func(*args, **kwargs)
    File "/usr/lib/python3/dist-packages/cloudinit/config/cc_growpart.py", line 298, in resize_devices
      (old, new) = resizer.resize(disk, ptnum, blockdev)
    File "/usr/lib/python3/dist-packages/cloudinit/config/cc_growpart.py", line 159, in resize
      return (before, get_size(partdev))
    File "/usr/lib/python3/dist-packages/cloudinit/config/cc_growpart.py", line 198, in get_size
      fd = os.open(filename, os.O_RDONLY)
  FileNotFoundError: [Errno 2] No such file or directory: '/dev/disk/by-partuuid/a5f2b49f-abd6-427f-bbc4-ba5559235cf3'

  ========================================

  @rcj suggested this is a race with udev. This seems to only happen on
  Cosmic and later.

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