Launchpad itself

lp test startup exhausts dev/random

Bug #662519 reported by Robert Collins
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Launchpad itself
Triaged
Low
Unassigned

Bug Description

I was investigating slow test startup and found the test process blocked on /dev/random.

lsof showed me this, which is a hint:

/usr/bin/ 24780 robertc 10r REG 252,1 3032 170190 /home/robertc/launchpad/lp-sourcedeps/eggs/dnspython-1.7.1-py2.6.egg/dns/entropy.py
/usr/bin/ 24780 robertc 11r CHR 1,8 0t0 971 /dev/random

That file uses random unconditionally; I don't know if we do/don't need crypto level randomness here in prod but we certainly don't for testing. Changing that to urandom saved 100 seconds from a parallel testrun of just a few tests.

Revision history for this message
Gary Poster (gary) wrote :

For my own notes, I suppose: The use of /dev/random is done once for seeding a module global, so dnspython is not using it indiscriminately. That said, if there's not enough entropy, there's not enough entropy. A way to switch the module to urandom (or just time, even) for tests would be nice.

Changed in launchpad-foundations:
status: New → Triaged
importance: Undecided → Low
Revision history for this message
Robert Collins (lifeless) wrote : Re: [Bug 662519] Re: lp test startup exhausts dev/random

On Tue, Oct 19, 2010 at 5:25 AM, Gary Poster <email address hidden> wrote:
> For my own notes, I suppose: The use of /dev/random is done once for
> seeding a module global, so dnspython is not using it indiscriminately.
> That said, if there's not enough entropy, there's not enough entropy.  A
> way to switch the module to urandom (or just time, even) for tests would
> be nice.

Does it do this in production? If so we should start recording how
long it takes - its possible (have done it before) to exhaust
dev/random on production, and *then* things really get hairy. Remember
we're looking at 16-32 instances starting up in very short order in
the branch new world.

-Rob

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