[Buildbot-devel] Intermittent Connection.Lost error with Windows slaves

Dmitry Mikhin dmitry.mikhin at gmail.com
Thu Sep 6 06:48:02 UTC 2012

Hello everyone,

I'm having some trouble with a (virtual) Windows slave.

- Master and slave on the same Fedora 14 box
- Windows XP under VirtualBox (LibVirtSlave)
- Buildslave v. 0.8.6p1 on slave, Buildbot 0.8.5, Twisted 11.1.0 on master
- PuTTY for establishing ssh tunnel to the master
- MyEnTunnel for automatically starting PuTTY (plink)

Generally works, but roughly every second build fails with the exception

[Failure instance: Traceback (failure with no frames): <class
'twisted.internet.error.ConnectionLost'>: Connection to the other side
was lost in a non-clean fashion.

Not much information in twistd.log files on either slave or master.
Master gets exception, reports slave as lost, then for some time
cannot substantiate the virtual slave. Slave log starts a new build as
if nothing happened in between.

All works stable with Linux slaves, all on the same physical host.

I tried the suggestions from
in particular:

- In buildbot.tac file, specified a higher keepalive value, 60000.

- Modified the Windows KeepAliveTime registry setting to a value of
60000 (had to create this DWORD registry entry, it did not exist

- Turned off Windows firewall.

- I cannot ensure that the master is never 100% busy, it's a multicore
box running multiple slaves. But failures do happen, roughly at the
same frequency, when I manually start this single Windows build and
not much else takes place.

Any suggestions? Any hints how to debug the issue?


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