[Bug 1269073] Re: test_tomcat_daemon smoke test failure on images with 3.13 kernel

[Robie Basak]

Useful reading: http://man7.org/linux/man-pages/man4/random.4.html and
http://en.wikipedia.org/wiki//dev/random

/dev/urandom does not block at the cost of not being the best quality
entropy. /dev/random is recommended for long term cryptographic use, but
at the cost of blocking if the kernel doesn't have enough entropy
available.

If the problem is that in general use Tomcat takes longer to start
listening on its socket (but is otherwise unaffected), then I think that
the immediate problem could be fixed in the test case. It could use the
symlink trick to simulate a system that does always have enough entropy
available.

Question: should the test case be checking that Tomcat works eventually
when enough entropy is provided, or that Tomcat starts listening quickly
on an entropy-starved system?

An obvious secondary problem for users is "so how do I get enough
entropy to get my VM running Tomcat to start listening faster, then?".
The answer to this is the same as always - from the usual sources,
including the option of an external hardware entropy source passed
through to the VM, or from some other external source and fed in to the
kernel from userspace.

A tertiary, perhaps blueprint-level item might be to make it easier for
users to get entropy to their VMs, in order to make Ubuntu VM use better
in general for all our users. This might involve us recommending a
method and making it more automatic, for example via cloud-init.

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Title:
  test_tomcat_daemon smoke test failure on images with 3.13 kernel

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