Christopher J. McClellan
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I run a bunch of Docker containers on a single CentOS 6 server with a limited amount of memory. (I only recently bumped it from 0.5 to 1 whole whopping gig!) Before I bring another container online, I like to check to see how much room I’ve got. Being the newest versions of Docker aren’t available for CentOS 6, I’m running an ancient version, 1.7 or so. On the new versions of Docker, running
docker stats will return statistics about all of your running container, but on old versions, you must pass
docker stats a single container id. Here’s a quick one-liner that displays stats for all of your running containers for old versions.
$ docker ps -q | xargs docker stats --no-stream CONTAINER CPU % MEM USAGE/LIMIT MEM % NET I/O 31636c70b372 0.07% 130.8 MB/1.041 GB 12.57% 269.7 kB/262.8 kB 8d184dfbeeaf 0.00% 112.8 MB/1.041 GB 10.84% 45.24 MB/32.66 MB a63b24fe6099 0.45% 50.09 MB/1.041 GB 4.81% 1.279 GB/1.947 GB fd1339522e04 0.01% 108.2 MB/1.041 GB 10.40% 8.262 MB/23.36 MB
docker ps -q returns the list of running container ids, which we then pipe through
xargs and into
docker stats. Adding
--no-stream gives us just the first result instead of continually updating the stats.
It’s a neat little trick. If anyone knows how to make this return container names instead of ids, please comment below.
Again, this is unnecessary for the newest versions. Just run
docker stats and you’ll get nearly identical output.
I realize that my posts here have become a bit infrequent and erratic. If you’re a frequent reader, you know that I changed jobs early this year. I didn’t just change jobs though; I completely swapped stacks. Learning a dozen technologies “overnight” has taken up a lot of the time that I previously dedicated to writing. I also had my first ever speaking engagement in May, just as my wife was finishing up her degree. Needless to say, we’ve been having a very busy year to date. I’ve simply not had the time or mental bandwidth to regularly update this blog. I tried, but I don’t feel like it’s been my best writing.
When I first started writing this blog, I had set myself a goal of one new post a month. That made a ton of sense at the time, but I never revisited that goal to make sure it still made sense. Even with everything else going on in my life, I (quite unintentionally) put pressure on myself to meet that goal. At some point this Spring I realized I couldn’t do it all and let some things slide.
It’s important to know where your limits are. There are only so many hours in a day. We must wisely choose what to do with them. I severely underestimated how much time it would take to prepare a presentation, which is funny, because it was largely about not doing “gut” estimations. I sacrificed time with my family and time writing here in order to share something I felt was important to share. Since then, I’ve been focused on making up for the lost time. In fact, we just got back from a fantastic camping trip.
Burn out is a common theme in software development. For all our talk about creating software at a sustainable pace, many of us are not moving at one. It’s not always our stakeholders and clients pushing us past our limits either. They’re an easy scapegoat, but in many cases, it’s us pushing ourselves past our limits. We’ll go in early, stay late, or log in from home to check on a long running process. We don’t say “no” often enough to though “aggressive” (cough impossible cough) deadlines. That’s our own fault. We’re responsible for our own health and well being. We’re responsible for creating a sustainable pace of development.
How long has it been since you’ve taken a vacation? I mean a real vacation, not a day here or there, or a week where you check your email and Slack five times a day, but one where you leave the laptop at home and shut off your phone for a week. How long has it been? My last one was at least seven years ago. Granted, I may be a workaholic, but that’s about six years too long without a break from it all. Creating software is a massively creative endeavor. How did I expect myself to remain creative without taking time to recharge those creative juices?! I don’t know. I’m some sort of idiot I guess, because I feel better than I have in years. I feel ready to solve problems and inspired to write again.
If it’s been a while since you’ve unplugged, I highly encourage you to do so. Take a few days and pretend it’s 1995. Navigate with a paper map to someplace new and exciting. Go hiking or visit a museum. Spend some extra time with your kids. Whatever recharges you, go do it. You won’t regret it.
~ Semper Cogitet
P.S. This was supposed to be an update about what’s coming up in the next few months, but I seemed to have found something more important to say in the process of writing this post. I do have a few technical posts on my todo list and at some point I intend on turning my Lean Estimates talk into a blog post. They’re coming, but not a huge priority for me at the moment. I’ll write them as time allows, however I have prioritized time with my family and some house hold chores over this blog. I expect to post one new blog about every 6-8 weeks instead of every 4-6. So hang tight while I find a sustainable pace for this blog.
Posted in Programming on May 13, 2017
I’m very much a “The tests pass. Ship it.” kind of guy. I like to fail fast and have long believed that the best way to find places where we missed a requirement or made a mistake is to get it into the hands of real users as quickly as possible. Recently however, the users are the folks sitting right next to me. I don’t mean a Product Owner either, I mean my team mates, my fellow devs. This has begun to really change my perspective a bit.
You see, we’re not building software. Sure, we are building software, but that piece is inconsequential. What matters is the output of that software, not the software itself. It’s just a means to an end, which also means that we operate the system, we’re its users. The ultimate form of eating your own dog food, if you will.
This means that if I break something, I not only have someone breathing down my neck, but I’ve also directly hurt my team and slowed us down. Obviously, this has given me lots of good reason to slow down and test a bit more thoroughly (manually, exploratorily) than I have in the past. I hope to continue to care this much about my users when they no longer sit right next to me again.
So dear reader, my challenge to you: Don’t treat your users like testers or guinea pigs. Treat them like you’d treat them if they sat next to you, worked with you, everyday. I’m willing to bet you’d delight them that much more.
Until next time,
Posted in Programming on April 30, 2017
Let’s talk about Code Reviews for a minute. They’re important; they spread knowledge around and catch bugs , but they can be frustrating some times. They don’t need to be though. There are a few things we can do to keep the code review a pleasant experience.
- Review the code, not the coder.
Keep it impersonal. Don’t use the words “you”, “your”, etc. Talk about the code. “This foo should handle this edge case.”, not “You forgot to handle this edge case.”
If you feel really compelled to use pronouns, always use “We”. It makes it clear that we both share the responsibility. “We need to handle this edge case here.”
- Don’t just point out flaws, offer improvements.
The most frustrating thing I run into is inactionable comments. “This foo is kind of ugly.” Yes. I know it’s ugly. It’s that way because I don’t know how to clean it up. We’re not learning via the Platonic method here. Please offer some suggestions on how we can clean it up. If I had known how, I would have likely already done so. If you don’t know either, offer to pair on it.
There you go, two quick tips for a better code review experience.
Until next time… Semper Cogitet
Posted in Programming on March 20, 2017
I’m not a big fan of integration tests. They’re often unreliable and “flaky” due to their very nature of being integration tests that rely on file systems, networks, and databases. These kinds of tests are hard to get right. At least, it’s hard to get them stable enough to be valuable and I often wonder if the gains outweigh the costs. However, there is one very useful thing integration tests can do for you. They can bring architectural smells to light. Do you need to bring up an entire (virtualized) cluster just to test one small component of your system? That’s a smell. Just like a unit test that needs to setup dozens of fakes, it’s a sign that your system is too tightly coupled.
I was recently working on a dashboarding application that talks to a Lucene based search engine. The QA team had been running their integration tests by spinning up an entire cluster, complete with dozens of other components. This was the only way for them to run the application and get data into it to work with. It takes around 20 minutes to get a local, dockerized, cluster running, so needless to say, I’m looking for ways to run just the parts I need. In other words, I needed to know if I actually needed the entire environment, or if I could just spin up an instance of the search engine for testing purposes.
It turns out that this was a couple of hours of work to create a much smaller docker network with just the search engine, proxy server, and the web app. It turns out that this section of the system is architected pretty well, but you wouldn’t have known it from looking at the tests. Indeed, many other parts of the “distributed monolith” really do need the whole cluster in order to function properly. I suspect that because most of the system requires dozens of components to be online, it was just assumed that this part of the system did too.
Tomorrow, I hope to finish automating those integration tests by whipping up a small docker-compose file and data seed script. This test setup should document exactly what is needed in order for this application to run. As for the tests that require dozens of components to run? Those tests are a testimate to why I’ve begun to lovingly call this system a “distributed monolith”.
Until next time,
I had a really amazing experience this week. I had an opportunity to pair with a gentleman who has been programming since I was in diapers. He had only ever test driven code once before, but is really excited about learning. I think that in and of itself is amazing, but I learned a few things during the experience as well.
Being it was his second time test driving, I navigated while he drove. He’s seen our team pair, and asked if we were going to ping pong (one of us would write a failing test, then the other make it pass), but I wanted him to build as much muscle memory as possible. A smile lit up his face and I can’t tell you how happy it made it me.
Our task was to parse a version number and increment the patch number on it. He immediately created a new file for the test, but I stopped him.
“Hey, wait a sec. Why don’t we take a few minutes to write a test list first?”
“What do you mean?”
“Well, I like to take a minute to think about the inputs, outputs, and edge cases, then write down any tests we think we should write. The test list is our roadmap. It keeps us on task. I don’t like Test Drive Design. I like to do just enough design first, then test drive the development.”
“Okay man. I can dig that. That’s smart. I never understood how TDD makes better code when you weren’t taking the time to design anything. So, what you’re saying is that TDD doesn’t mean “don’t design at all”, but “design just in time”, right?”
“Yeah. I guess I am. Something like that anyway.”
I’ve said before (perhaps not on this blog, but before and relatively often) that TDD doesn’t excuse us from good design. What I hadn’t realized is the “just in time” part. Just like everything else in my development cycle, I’m doing just enough, just in time to be most effective, yet still as lightweight as possible. It’s interesting and I’m surprised it never dawned upon me before.
Anyway, we create a test list and finally he gets to create that test class he was so eager to create. Even though he’d barely done this before, he instinctually created the test class first. I know I had to have been smiling as I watched him. “This guy’s a natural”, I thought to myself. He copied just enough code from a neighboring test class to get the test runner to pick it up and then I had him delete any extra remnants of the other test. We paused for a moment and I asked him to pick out what he thought would be the simplest test to write. He picked one and began writing the test, beginning with creating an instance of our not yet existent class.
“Whoah! Hold up! You’ve got a failing test.”
“What do you mean? There is no test yet!”
“Yes there is, and it’s failing. That code won’t compile. A test that won’t compile is a failing test.”
He smiled. “Okay man. I’m picking up what you’re laying down. Write just enough to make it fail, right?”
There it is again. Do just enough, just in time….
So, he created the new class, ran the no-op test, and went back to writing the test. Soon, we also had a no-op function and a failing test that actually tested something meaningful.
“Okay. Now let’s make this pass.”
“Sure. Now let’s see. We’re going to need to split this string and..”
“Whoah! Slow down a little. Is that really the simplest way to make this test pass?”
“What do you mean?”
“Well, why not just hard code the return value?”
He looked at me like I was totally nuts. Maybe I am….
“Huh? I don’t get it.”
“If we hard code the return value, the test will pass. Then, we’ll go back and add a new test that forces us to change the code. If we start splitting strings right now, we might accidentally write code that isn’t tested.”
“Hmm…. I don’t know man, but you’re the expert. All right, let’s just hard code it for now.”
He reminded me of just how counter intuitive TDD can be when you’re new at it. Heck, it can be counter intuitive when you’re experienced at it. I’ve been doing this for years and I still feel weird hard coding that return value, but I’ve also burnt myself by writing more code than absolutely necessary to make a test pass. This is a nice reminder of just how much discipline it takes to test drive.
We test drove this little function for about an hour, writing just enough code to make it fail, then just enough to make it pass. At the end of that hour, we had about a dozen tests and I could see the concern growing on his face. I had a feeling that I knew what was coming.
“Man. These tests are great, but the implementation code sucks. It’s downright awful. Are you sure about this TDD stuff?”
“Yeah. That code does suck, doesn’t it. Let’s fix that. So far we’ve been skipping the refactor step. I wanted you to get the feel for the red/green cycle. I probably should have stopped us sooner, but you were having fun and building muscle memory.”
We spent 15 or 20 minutes refactoring the code until we had something not quite as nasty as before.
“Dude. That was awesome! We just completely tore the guts out that code and it still works! More importantly, I know it still works, because the tests are green. Not bad man, not bad at all. I can see why you young guns like this so much.”
This is something that strikes me often about test driven code. Test driven implementations tends to be ugly as sin. I mean, downright bad, rotten, spaghetti code implementations, but we have the tests. We can refactor. Hell, I’ve deleted entire implementations and started over, knowing that when I was done, I’d have working code again, because I have the tests. The ugly implementation is only a problem if we skip the refactor step. Don’t skip it. Even if there’s nothing to refactor, be sure to take a moment to double check that there’s nothing to refactor yet. It’s really important to build that habit. Next time I teach someone TDD, I’ll be sure to make it an explicit part of our cycle from the very beginning.
We continued on like this for the rest of the afternoon. By the end of the day, we had a really bullet proof implementation ready to merge in.
“So, Chris… This is really great and all. I mean, I had fun man, but it took us all afternoon to write that one function. Is this really worth it?”
“Well, you’re right. It took a long time to write that, but let me ask you something. All those edge cases we found… If we had whipped up the 30 minute version of this function, without test driving, would we have thought of them?”
“No. No way.”
“When would we have thought of them?”
“Months from now when someone reported a bug.”
“Right. Months from now, when…”
“When we’ve forgotten all about this code and not only will it be more expensive to fix, but it’s also caused real damage out in production.”
“Exactly.” I said with a smile on my face.
An old dog learned a new trick this week, and this pup learned some valuable lessons as well. I’m looking forward to pairing with him again. I’ve a feeling we’ve got a lot to teach each other.
Posted in Programming on January 22, 2017
The monk Ahiru was pairing with the bright young apprentice, Taipisuto. The apprentice was quite impressed with his customized editor and the speed at which he could type. Ahiru was not nearly as impressed. The screen was flickering in a way that made him more than just a bit nauseous.
“And what shall you do when you’re assigned to a clan and they use a different editor? How will you pair with them?”, asked Ahiru of the apprentice.
“I shall teach them the vastly superior ways of Emacs”, replied the apprentice matter of factly. “It allows us to type very quickly with almost no effort at all! How can anyone deny this?!”
Ahiru quashed his desire to strike the young man. He appreciated his confidence, but the young apprentice had a lesson to be learned. That night, Ahiru committed the worst of sins. He rebased the clan’s master branch, eradicating the work the apprentice and he had done that day and making it impossible to easily restore it from the apprentice’s local fork.
When the monk arrived the next morning, the apprentice was visibly distraught, his fingers flying over the keyboard in pure desperation.
“What’s wrong?” asked Ahiru, knowing full well what he had done.
“Our commits!”, cried the apprentice. “They’re gone! Someone committed the sin of all sins and rebased the master branch! We’ve lost an entire day’s work! Who can have done this?”, he moaned.
“Null.“, said Ahiru. “We’ve simply lost the code. The work has not been lost.”
The apprentice just stared at the monk, not understanding the words he had just heard.
“90% of what we do is think about how to solve a problem, Taipisuto. The temple does not pay us to write code, they pay us to solve problems, and solve the problem we did.” Ahiru slid down into his seat next to the young man. “Now, let us re-implement the code. How long do you think it will take us?”
“It took us all day yesterday to write it…”, the apprentice bemoaned again. This time, Ahiru did not restrain himself and came down swiftly on the top of Taipisuto’s head with his staff.
“Type.”, said Ahiru.
Half an hour later, as the pair were checking the newly re-implemented code into the clan’s master branch, the apprentice was enlightened.
I’m a big fan of The Codeless Code and since they’ve not posted anything new in a while, I thought that I’d try my hand at their style of “programmer’s koan”. Following their lead, the story above is provided under the Creative Commons Attribution-NonCommercial 3.0 Unported License.
About 8 months ago, I promised you that I’d follow up and let you know how our transition to Agile software development was going. This is that long overdue follow up and I’m sad to say that six weeks ago I submitted my resignation. Tomorrow I start with my new company.
I’m sitting in an airport right now reading Brad Warner’s “Hardcore Zen” for the dozenth time and I think I’m finally ready to talk about all this. I’ve been trying to figure out what to say for over a month. I know I need to write about this, but I’ve not had the words until now. It turns out, that it’s fairly simple.
I failed. I failed. I failed. I learned, my team learned, we found an incredible amount of success, then we failed. Then I failed in the worst possible way: I gave up.
The whole goal of my hobby site is to iteratively create the simplest website that could possibly work using all “new to me” stacks. Getting a static site up and running on my own Linux CentOS with Lighttpd was definitely simple. Getting a NodeJs web service up and running with Express was equally simple, but making it production quality was definitely a frustrating experience for me.
My initial experience with NodeJs was exhilarating. I had a web server & app running with just a few lines of code, but then I quickly soured on the whole platform when I found TDD & mocking to be more difficult than I feel it should be. I’m happy to say that through a bit of research and effort, I now have a stack that I’m relatively happy with. I want to capture the struggles and solutions while they’re still fresh in my mind.
I’ve been building a hobby site so I can learn about non-Microsoft stacks and I spent the weekend learning Node.js. At first I was completely amazed at how awesome it was. It took about 5 minutes to spin up a webserver and start returning HTML from an endpoint! It was easy and fun! That 5 minutes of fun ended as soon as I thought “okay, now let’s write some production quality code”.
This ugly solution was bothering me, so I dug my heels in and went searching for a more idiomatic way to accomplish DI. What I found was Proxyquire. Proxyquire isn’t really DI. It works much in the same way you’d break a C `imports` dependency by creating a fake and telling the linker to use your fake instead. Only, of course, Proxyquire does this at run time instead. The documentation is good, but not great and it took about about an hour to get it working properly. It was a rather frustrating experience.
So, with a way to fake dependencies in hand, I get to writing an actual assert statement. That’s when I hit the next wall. Express’ way of sending responses doesn’t actually return anything. It all works via side effects. So now I could go install Sinon and learn a 4th library or I could just not write the tests because I’m not having fun anymore. Wasn’t that why I fell in love for that brief moment? Didn’t I love Node a few hours ago because it was easy and fun?
That doesn’t mean that I don’t have a use for Node.js though. I would absolutely use it to quickly prototype an idea. It’s completely fantastic for getting something simple up and running quickly. However, I would then just as quickly throw that prototype in the trash and write my production code in something else. A platform being quick, fun, and easy doesn’t matter if it’s hard to do things the right way. If it’s easier to write tightly coupled and untested code, we will. I don’t know about you, but I like knowing my code works and will continue to work.