UK Oracle User Group


UKOUG Tech13 WebLogic Hackathon - the networking behind the scenes

9 December 2013

Last Sunday at UKOUG Tech13 we ran a "WebLogic Hackathon". Read the full post by Simon Haslam

This started with Peter Lorenzen showing people how to install the JDK and WebLogic, and then create a domain - all done silently (i.e. with graphical screens and user interaction). After this Ronald van Luttikhuizen and I, ably assisted by Pete and Guido Schmutz, ran a session to use eitherPuppet or Chef, both popular automation tools, to do the same thing on 3 nodes entirely automatically. Delegates worked in groups of 3 with the VirtualBox images and various other files distributed centrally from my ThinkPad. One common factor to all three sessions was the network so I thought it might be amusing to describe a little about our adventures that morning.

As organisers we started the day at around 10ish. Note the happy, unstressed looks (and the single switch...):

Ronald, Guido, Peter, simon
From L-R: Ronald van Luttikhuizen, Guido Schmutz, Peter Lorenzen, Simon Haslam

 We all got started and in less that an hour later we mostly had the network cabled up.

Guido & Simon - network guys 

This photo below is the last we have (at 10:51am) of the cabling, though after this point they were neatly bunched into groups to each of the 4 tables (partly for health and safety reasons, partly due to my mild OCD!). You can also see my orange ADC PremisNet CAT6 patch cable (very reliable by the way) trailing to a switch uplink port.

Hackathon network - halfway there

My laptop was running a virtual machine which provided a DHCP server, a DNS server and an HTTP server. For the delegates' VMs to connect to the network properly and get a hostname we needed the DHCP and DNS. (On Red Hat style OSes by default they will do a DHCP request to get an IP address for eth0, and then an rDNS request using that IP to find out their hostname). 

At this point the fun began! Pete's laptop couldn't get a full DHCP negotiation with my server. I forget now whether we saw the broadcast but not the response, or nothing at all. Anyway, after a series of red herring investigations, by about 11:30 we realised that there was something wrong with the (venue supplied) ~48 port D-Link switch - the lights were on and blinking, but it was definitely not working properly. To prove the point we rigged up an alternate switch that fortunately Pete had with him:

 Alternative (working) switch

In the meantime the AV guy went off to try to find another switch. By about noon he had found another couple of smaller switches so we then frantically had to try to re-patch them before the 25 registered delegates arrived! One of the challenges with all this unlabelled grey cabling was identifying the cables we had connected up so that people didn't waste time with dead ones.

I think it was about 12:20 by the time we were properly up and running, though by that point any hope of half decent cable management had gone right out of the window:

Not a pretty sight!

So, in the end, we were just about ready for our 12:30 start! After a few niggles with the networking configuration in the images, everyone was soon connected and racing to finsh the hackathon:

UKOUG Tech13 WebLogic Hackathon in full flow

We never did find out what was wrong with the original switch. We knew that a lot of the patch cables supplied by the venue had been recently manually crimped, so one (untested) theory is that maybe there were a few cable faults driving down the voltage on the switch. Alternatively I'm wondering if there was some configuration somewhere (I didn't look at the time to see if this was a managed or unmanaged switch) blocking the DHCP broadcast. If anyone has any other ideas feel free to put me out of my misery with a comment!

If you'd like a little more idea of what we did Bob Rhubart, of OTN fame, published a video:

Bob also filmed an interview with the triumphant winners!

Overall the WebLogic Hackathon was a lot of fun, though the "hacking" element started rather sooner than I'd expected. We also learnt a few things along the way and maybe we should run the WebLogic Hackathon again... but take a spare switch with us next time! 

By: Simon Haslam | VIA: www.veriton.co.uk

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