[Bug 1743249] Re: Failed Deployment after timeout trying to retrieve grub cfg

[Mike Pontillo]

Ah, I see what you mean there; I used the following filter in Wireshark:

    udp.dstport == 25305 or udp.srcport == 25305

This is not the behavior I saw if the TFTP request is answered in a
timely manner, so I suspect that the long delay between the initial
request and the answer is causing the timeouts to occur in the TFTP
code, which causes this separate "stacked OACK" bug.

By the time the "stacked OACKs" are sent, it's been over one minute, and
the client isn't listening for a reply any more. So yes, "stacked OACKs"
are a real bug, but right now I think they're just distracting from the
root cause (the long delay).

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https://bugs.launchpad.net/bugs/1743249

Title:
  Failed Deployment after timeout trying to retrieve grub cfg

Status in MAAS:
  New
Status in grub2 package in Ubuntu:
  In Progress

Bug description:
  A node failed to deploy after it failed to retrieve a grub.cfg from
  MAAS due to a timeout.  In the logs, it's clear that the server tried
  to retrieve the grub cfg many times, over about 30 seconds:

  http://paste.ubuntu.com/26387256/

  We see the same thing for other hosts around the same time:

  http://paste.ubuntu.com/26387262/

  It seems like MAAS is taking way too long to respond to these
  requests.

  This is very similar to bug 1724677, which was happening pre-
  metldown/spectre. The only difference is we don't see "[critical] TFTP
  back-end failed" in the logs anymore.

  I connected to the console on this system and it had errors about
  timing out retrieving the grub-cfg, then it had an error message along
  the lines of "error not an ip" and then "double free".  After I
  connected but before I could get a screenshot the system rebooted and
  was directed by maas to power off, which it did successfully after
  booting to linux.

  Full logs are available here:
  https://10.245.162.101/artifacts/14a34b5a-9321-4d1a-b2fa-
  ed277a020e7c/cpe_cloud_395/infra-logs.tar

  This is with 2.3.0-6434-gd354690-0ubuntu1~16.04.1.

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