Working at RedHat

So this happened:

James just James at RedHat headquarters in North Carolina

James just James at RedHat headquarters in North Carolina wearing his new red hat.

RedHat made me an offer, and I am happy to say that I have just started this week!

I am proud to have joined a company that employs many of the worlds foremost, highly professional and clever hackers. It is indubitably the best Free Software [1] / Open Source company out there, and they ship some of the greatest and most elegant software available.

Happy hacking,

James

[1] Since free software is not a matter of price, a low price doesn’t make the software free, or even closer to free. So if you are redistributing copies of free software, you might as well charge a substantial fee and make some money. Redistributing free software is a good and legitimate activity; if you do it, you might as well make a profit from it.

Puppet-Gluster now available as RPM

I’ve been afraid of RPM and package maintaining [1] for years, but thanks to Kaleb Keithley, I have finally made some RPM’s that weren’t generated from a high level tool. Now that I have the boilerplate done, it’s a relatively painless process!

In case you don’t know kkeithley, he is a wizard [2] who happens to also be especially cool and hardworking. If you meet him, be sure to buy him a $BEVERAGE. </plug>

A photo of kkeithley after he (temporarily) transformed himself into a wizard penguin.

A photo of kkeithley after he (temporarily) transformed himself into a wizard penguin.

The full source of my changes is available in git.

If you want to make the RPM’s yourself, simply clone the puppet-gluster source, and run: make rpm. If you’d rather download pre-built RPM’s, SRPM’S, or source tarballs, they are all being graciously hosted on download.gluster.org, thanks to John Mark Walker and the gluster.org community.

These RPM’s will install their contents into /usr/share/puppet/modules/. They should work on Fedora or CentOS, but they do require a puppet package to be installed. I hope to offer them in the future as part of a repository for easier consumption.

There are also RPM’s available for puppet-common, puppet-keepalived, puppet-puppet, puppet-shorewall, puppet-yum, and even puppetlabs-stdlib. These are the dependencies required to install the puppet-gluster module.

Please let me know if you find any issues with any of the packages, or if you have any recommendations for improvement! I’m new to packaging, so I probably made some mistakes.

Happy Hacking,

James

[1] package maintainer, aka: “paintainer” – according to semiosis, who is right!

[2] wizard as in an awesome, talented, hacker.

Introducing Puppet Exec['again']

Puppet is missing a number of much-needed features. That’s the bad news. The good news is that I’ve been able to write some of these as modules that don’t need to change the Puppet core! This is an article about one of these features.

Posit: It’s not possible to apply all of your Puppet manifests in a single run.

I believe that this holds true for the current implementation of Puppet. Most manifests can, do and should apply completely in a single run. If your Puppet run takes more than one run to converge, then chances are that you’re doing something wrong.

(For the sake of this article, convergence means that everything has been applied cleanly, and that a subsequent Puppet run wouldn’t have any work to do.)

There are some advanced corner cases, where this is not possible. In these situations, you will either have to wait for the next Puppet run (by default it will run every 30 minutes) or keep running Puppet manually until your configuration has converged. Neither of these situations are acceptable because:

  • Waiting 30 minutes while your machines are idle is (mostly) a waste of time.
  • Doing manual work to set up your automation kind of defeats the purpose.
'Are you stealing those LCDs?' 'Yeah, but I'm doing it while my code compiles.'

Waiting 30 minutes while your machines are idle is (mostly) a waste of time. Okay, maybe it’s not entirely a waste of time :)

So what’s the solution?

Introducing: Puppet Exec['again'] !

Exec['again'] is a feature which I’ve added to my Puppet-Common module.

What does it do?

Each Puppet run, your code can decide if it thinks there is more work to do, or if the host is not in a converged state. If so, it will tell Exec['again'].

What does Exec['again'] do?

Exec['again'] will fork a process off from the running puppet process. It will wait until that parent process has finished, and then it will spawn (technically: execvpe) a new puppet process to run puppet again. The module is smart enough to inspect the parent puppet process, and it knows how to run the child puppet. Once the new child puppet process is running, you won’t see any leftover process id from the parent Exec['again'] tool.

How do I tell it to run?

It’s quite simple, all you have to do is import my puppet module, and then notify the magic Exec['again'] type that my class defines. Example:

include common::again

$some_str = 'ttboj is awesome'
# you can notify from any type that can generate a notification!
# typically, using exec is the most common, but is not required!
file { '/tmp/foo':
    content => "${some_str}\n",
    notify => Exec['again'], # notify puppet!
}

How do I decide if I need to run again?

This depends on your module, and isn’t always a trivial thing to figure out. In one case, I had to build a finite state machine in puppet to help decide whether this was necessary or not. In some cases, the solution might be simpler. In all cases, this is an advanced technique, so you’ll probably already have a good idea about how to figure this out if you need this type of technique.

Can I introduce a minimum delay before the next run happens?

Yes, absolutely. This is particularly useful if you are building a distributed system, and you want to give other hosts a chance to export resources before each successive run. Example:

include common::again

# when notified, this will run puppet again, delta sec after it ends!
common::again::delta { 'some-name':
    delta => 120, # 2 minutes (pick your own value)
}

# to run the above Exec['again'] you can use:
exec { '/bin/true':
    onlyif => '/bin/false', # TODO: some condition
    notify => Common::Again::Delta['some-name'],
}

Can you show me a real-world example of this module?

Have a look at the Puppet-Gluster module. This module was one of the reasons that I wrote the Exec['again'] functionality.

Are there any caveats?

Maybe! It’s possible to cause a fast “infinite loop”, where Puppet gets run unnecessarily. This could effectively DDOS your puppetmaster if left unchecked, so please use with caution! Keep in mind that puppet typically runs in an infinite loop already, except with a 30 minute interval.

Help, it won’t stop!

Either your code has become sentient, and has decided it wants to enable kerberos or you’ve got a bug in your Puppet manifests. If you fix the bug, things should eventually go back to normal. To kill the process that’s re-spawning puppet, look for it in your process tree. Example:

[root@server ~]# ps auxww | grep again[.py]
root 4079 0.0 0.7 132700 3768 ? S 18:26 0:00 /usr/bin/python /var/lib/puppet/tmp/common/again/again.py --delta 120
[root@server ~]# killall again.py
[root@server ~]# echo $?
0
[root@server ~]# ps auxww | grep again[.py]
[root@server ~]# killall again.py
again.py: no process killed
[root@server ~]#

Does this work with puppet running as a service or with puppet agent –test?

Yes.

How was the spawn/exec logic implemented?

The spawn/exec logic was implemented as a standalone python program that gets copied to your local system, and does all the heavy lifting. Please have a look and let me know if you can find any bugs!

Conclusion

I hope you enjoyed this addition to your toolbox. Please remember to use it with care. If you have a legitimate use for it, please let me know so that I can better understand your use case!

Happy hacking,

James

 

Preserving your working directory in gnome-terminal

I use gnome-terminal for most of my hacking. In fact, I use it so much, that I’ll often have multiple tabs open for a particular project. Here’s my workflow:

  1. Control+Alt+t (My shortcut to open a new gnome-terminal window.)
  2. cd ~/code/some_cool_hack/ # directory of some cool hack
  3. Control-Shift-t (Shortcut to open a new gnome-terminal tab.)
  4. Hack, hack, hack…

The problem is that the new tab that I’ve created will have a $PWD of ~, instead of keeping the $PWD of ~/code/some_cool_hack/, which is the project I’m working on!

The solution is to add:

# including this ensures that new gnome-terminal tabs keep the parent `pwd` !
if [ -e /etc/profile.d/vte.sh ]; then
    . /etc/profile.d/vte.sh
fi

to your ~/.bashrc. Now everything works perfectly!

Many thanks to Matthias Clasen and Ray Strode for figuring this one out!

One side note: this used to be the default, but for some reason it broke around Fedora 19 or 20. Maybe it had to do with my fancy prompt, but everything is working great now.

Happy Hacking,

James

 

Speaking at SCALE today!

I’ll be giving a talk at SCALE today about automatically deploying GlusterFS with Puppet-Gluster and Vagrant. I’ll be giving some live demos, and this will cover some of the material from:

Automatically deploying GlusterFS with Puppet-Gluster + Vagrant!

and it will contain excerpts from:

Screencasts of Puppet-Gluster + Vagrant

I’ll also be talking about some new upcoming features, and am happy to answer all of your questions!

The talk will be part of Infrastructure.next and is starting around 1:30 or 2pm in the Century AB room.

If you’re not able to attend, or you’d like a more personalized demo, send me a note! I’ll be around for the next few days.

Thanks to Joe Brockmeier and John Mark Walker for hosting the event and sending me here.

Happy Hacking,

James

 

Building a snow shelter

To give you a break from the usual GNU/Linux/DevOps/Puppet/GlusterFS drab, I’ve decided to have a go at writing a different kind of technical article. This article will show you how to build the traditional Canadian snow dwelling known as a quinzee. If you will be travelling to Canada, I recommended that you read through this article ahead of time, so that you don’t offend your host by being unfamiliar with their traditional living accommodations.

Warning:

If you are not Canadian or if it is your first time building this type of shelter, I recommend that you have a professional supervise and guide you! If it is not sufficiently cold out (less than 0oC) when you are building or sleeping in your shelter, it could collapse, squashing and suffocating you! If it’s built correctly, a quinzee can safely support the weight of many people, although it is not intended for use as scaffolding. When you are inside the quinzee digging, you must have a buddy outside, standing watch for your safety, in case of quinzee collapse or polar bear attack.

Fresh snow:

Start off by choosing a place to build your quinzee. Usually you’ll build your quinzee near the other quinzees in the village, however for this article, I have decided to set up in a remote location, as this will be used as my vacation home. It is good to build on flat terrain, where there is a lot of fresh snow. In Canada, there is always an abundance of snow so it should be easy to find a pristine area.

Fresh snow

Fresh snow

If you build in a wooded area, be sure that there are no trees or dead branches that might fall or break off in the wind and squish you or your quinzee!

Stratification:

With each snowfall, new layers of snow are deposited onto the older layers which is called stratification. Since each layer could have different consistencies or strengths, it is important to mix or break up the layering before we build our quinzee. This will make sure that the walls of the quinzee are stable, and don’t shift later on.

Destratification of the snow

Destratification of the snow

Here, the layers of snow are destratified with a shovel, in a circle of about two to three metres in diametre. This circle will be the outside size of your quinzee. A three metre diametre quinzee would more than comfortably fit three large sleeping Canadians, which is the equivalent of two standard polar bears wide.

Piling the snow:

To make a quinzee, you need a large pile of snow. You’ll want to shovel the snow from outside of the destratified quinzee circle, into the centre of the pile. Work your way around the circle, gradually moving outwards as you need more snow. This technique has the added advantage that the area outside of your quinzee will be cleared of snow, and gives you room for stargazing, polar bear watching, and other typical Canadian pastimes.

A pile of snow

A pile of snow

After a few hours your pile will grow large enough that it should be about two to three metres high. You don’t have to worry about the specific height as long as you always throw the snow on the top of the pile. The pile will automatically spread out to form a larger diametre base if it is too high to be supported on a smaller base.

Some quinzee builders will pile their backpacks and other equipment in the centre of the pile under a tarp before piling on the snow. This is a tricky optimization, but if done correctly, there will be less snow to shovel onto the pile, and less snow to dig out at the end.

Large snow pile

A larger pile of snow

When not in use, make sure you don’t leave shovels or other items lying around on the ground, as they could easily get covered up by snowfall and lost forever. Conveniently, shovels can be stuck into the snow, where they’ll stand upright and remain visible.

At this point your pile of snow should now be complete. Congratulate yourself on a job well done and award yourself with a cool mug of maple syrup.

Sticks:

When digging out the quinzee, we’ll need to know how much snow to remove so that we don’t create unwanted windows in the wall of the shelter. To help keep track of the wall thickness, first gather about 40 to 50 sticks, each about 30cm in length. Insert all the sticks in the wall of the quinzee spaced out about 30cm from one another, and all pointing towards the centre of the shelter.

Sticks inserted into the pile of snow

Sticks inserted into the pile of snow

If the sticks are longer than 30cm, it’s okay if they protrude from the outside of the shelter. If they are too short, you can use them for firewood. When we dig out the shelter, we should encounter the sticks from inside the quinzee. Whenever you see a stick, you should stop digging in that direction.

Compaction:

At this point the quinzee needs time to settle. It typically takes between two and six hours. In this time, the snow crystals will lock together under their own weight, and the structure will harden because of the cold.

Waiting for compaction

Waiting for compaction

Although not easily noticeable, the structure may shrink due to this compaction. This is usually a great time to prepare lunch!

Lunch:

A typical Canadian meal might consist of bannock cooked on a stick, Montreal bagels, poutine, and a glass of maple syrup. Dessert is usually tire, served on snow. When your quinzee has sufficiently compacted, it’s time to start digging it out. If your quinzee needs more time to settle, then you can keep busy by gathering some firewood or practising your favourite Canadian song. While gathering a little firewood, I had a chance to take a quick photo looking down the main street of my village. On the right you can see some of the kindling I’ve collected, and in the distance to the left you can see a quinzee.

Main road of my village

Main road of my village

Digging:

You typically want as small of a door opening as you can fit through. Start digging near, but above the base of the quinzee at a downward angle towards the centre. As you reach the centre, start digging outwards in all directions. The downward angle will prevent strong winds from blowing directly into the quinzee. The inner dome will keep heat from escaping. It takes some experience to get the shape right, but after years of practice, you’ll quickly become an expert.

Cross sectional diagram of a quinzee

Cross sectional diagram of a quinzee

This process should take you about an hour. When you are digging inside of the quinzee, remember to always have your buddy on the outside in the event of collapse. While collapses are rare, they can happen, in particular if the weather is too warm, if you didn’t let your quinzee settle for long enough, or if you made your walls too thin or your roof too thick. It is important that your buddy pay attention, because the quinzee insulates you from sound (and cold) very well. To demonstrate this, scream or talk loudly while you’re inside the quinzee. Your buddy will not be able to hear you very easily.

Entrance to the quinzee

Entrance to the quinzee

During the day, if you ask your buddy to seal off the entrance with their body, it will be very dark inside the quinzee, but you should be able to see faint blue areas where the walls are the thinnest and some light is coming in. You probably don’t want to dig much further in those areas.

Finishing up:

When you are finished digging out your quinzee, pull out one of the sticks in the roof to create an air hole for ventilation. You’ll probably want to gently smooth out the inside walls and roof with your gloved hand. This will prevent the jagged digging marks (snow stalactites) from dripping on you once you’re sleeping in the quinzee and your body heat is causing them to melt.

View from inside the quinzee

View from inside the quinzee of the door

As a related optimization, some quinzee builders like to light a candle in the centre of the quinzee for a few hours to try to melt any variations on the inner walls, causing a glaze and preventing dripping.

Making it a home:

It’s customary to line the bottom of your quinzee with either a tarp, or if it’s available, some hay. The hay is a particularly comfortable bedding material because it soaks up excess moisture which would otherwise make your floor damp. In general, Canadians only line their quinzees with hay when royalty or a special guest is coming to visit. If you do not receive any hay when staying over at a friend’s place, please do not be offended as it is hard to come by in a country that has a winter climate for most of the year.

Looking into the quinzee

Looking into the quinzee

To get in and out of your quinzee it is customary to crawl or slide in on your stomach. In the above photo, an inconsiderate guest decided to “walk” on their hands and knees, causing damage to the door. In some Canadian villages, damaging a neighbours door can be a great insult and has led to at least two serious incidents. [1] [2]

For sleeping, orient your feet so they are closest to the door, and with your head away from it. When multiple people are lying next to each other in this way, the quinzee can be quite warm during cold winter nights.

Conclusion:

If you plan on leaving your home unattended for some time, it is common practice to destroy your quinzee so that small animals or children don’t get accidentally trapped inside should it be left unsupervised. Sadly, only a few days after I took these photos, a polar bear attacked my village and destroyed the quinzee!

What remained after a polar bear attack

What remained after a polar bear attack

One positive outcome of the attack is that you can get a good look inside the quinzee and you see a nice cross-section of the walls. Fortunately, this won’t cost me much in building materials, but it will be some time before I have time to rebuild, and even longer before I have time to get a guest quinzee built!

I hope this has been an instructional article! Stay warm, stay safe, and

Happy Hacking,

James

Scathing review of the Lenovo X240

I’m using a Lenovo X201 with 8GiB of RAM. Apart from some minor issues, I’ve been very satisfied with this laptop. It’s over four years old, and so I decided to see what’s available on the horizon. I did not buy an X240 because of the following reasons:

The X240 has only one slot for RAM and thus supports a maximum of 8GiB.

I think it’s pretty ridiculous for any successor to the X230 to support less RAM. In and of itself this is a deal breaker! My X201 has 8GiB, and I wish it had more! It doesn’t make sense to settle for less on new kit. In other words, Lenovo is stating that 8GiB ought to be enough for anybody.

The X240 keyboard is missing buttons.

The X201 keyboard has PageUp and PageDown keys in addition to the Forward and Back buttons which are located above the Left and Right arrow keys. It also has dedicated Insert and Delete keys. This is all to be expected, and is awesome.

The X240 removes the dedicated Forward and Back buttons, and replaces them with the (now relocated) PageUp and PageDown keys. To use the Forward and Back buttons, you now need an extra finger to hold the Fn button.

If that wasn’t bad enough, the Insert key now shares a button with the End key, which makes common Shift+Insert sequences near impossible to anyone that isn’t either a cephalopod or an Emacs user. Time to update the pedals to include an Fn key.

The X240 keyboard is missing buttons.

The X240 keyboard is missing buttons.

It’s also worth mentioning that the dedicated volume controls are gone.

The X240 has a new, incompatible power adapter.

Lenovo has decided it needs to squeeze more money out of users by introducing new, backwards-incompatible technology. To this end, the well-known barrel adapter is now gone, and it has been replaced by a strange rectangle. You might as well throw out all your old power bricks, as Lenovo has said they won’t offer a compatibility adapter. Apparently, they used to sell such an adapter, but it has been discontinued.

The X240 has a new, incompatible docking bay.

If you were a fan of docking, you’ll now have to purchase a new bay.

The X240 has a combined microphone/headphone jack.

Minimalist designs and the abundance of cheap phone headsets has reduced the dual jack design to a combined single jack. I don’t like the change, but I realize there’s not much that can be done to prevent it.

The X240 “Trackpad”/”Touchpad” is now buttonless.

I haven’t had a chance to try the new Touchpad, however the physical buttons are gone, and many users are complaining about the new feel of the pad. This feels like an attempt to imitate the look of an Apple product, instead of trying to maintain the functionality of the X series.

Lenovo has a terrible warranty program.

Getting a hardware replacement with the Lenovo “return to depot” service can take about two weeks. Bringing your laptop in to a service centre is equally challenging. The locator database is out of date, and once you do find a service centre, many are unwilling to accept your hardware because they’re backlogged with work! If you are lucky enough to get a part replaced, hope that it isn’t defective or DOA. I had to go through three rounds of bad motherboards graphics on my X201. The on-site service is a good option if you can afford it.

Conclusion

Instead of iterating and improving on the much-loved X series, Lenovo has decided to sacrifice its followers in trying to appeal to a low-end laptop market. Once the model of power and portability, the X series is now designed for users who are afraid of having too many buttons or too much RAM.

The X220 and X230 are not available for sale anymore. The X250 isn’t due before 2015. I’ve extended the warranty of my X201 to the maximum of five years. Let’s hope someone at Lenovo reads this article and can make a difference before it’s too late. I’m happy to consult and demo new hardware if you contact me. I’d genuinely like to help.

Happy Hacking,

James