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

[Michael Hudson-Doyle]

On another tangent, I wonder if the change that brought this to light
was the switch to booting without initrd. The timing is about right, and
fits with the fact that it doesn't occur with the generic kernel (which
cannot boot without initrd in Azure). So if someone has an excess of
time to test <wink>, testing bionic but with initrdless boot and focal
with initrdful boot would be interesting. I don't know exactly what
runes have to be cast to do this.

Getting the udevd debug output is still higher priority though.

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Title:
  cloud-init growpart race with udev

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

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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