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I always refer to Kubernetes as a framework for building distributed systems, and one popular use of that framework for most people has been deploying applications via containers. But nothing's stopping you from imagining new systems that do different things. |
**Erik St. Martin:** That's one of the things I'm particularly interested in, seeing what comes from Kubernetes as a continues to scale outward. Like you said, the current consensus from most people is that you just set it up on your machines and you throw your containers at it. And I'm really happy to see more use cas... |
I think we're gonna see some really interesting things come out over the next couple years. Even Kubernetes itself has changed a bit. Things like PetSets are getting introduced... |
**Kelsey Hightower:** I'm gonna touch on that topic for a second... So in my view, Kubernetes is super, super small. Just like Golang has a standard library, but the core language itself is really small. So if we were to think about the core of Kubernetes, it's also super small. We have maybe four or five - depending o... |
Then we have this other object, something that says "Keep one of those pods running at all times" or "I would like to have five of those pods running." That would be another object type. |
The other objects, it's very debatable whether they're really core concepts or not, because you see that we have extensions in Kubernetes. A deployment will be an extension. A service will be more of a core thing, so something that drives "This collection of applications belong to the same service." So once you have th... |
\[00:19:51.03\\\] A deployment or a PetSet - those are more workflows on top of those other objects. Those become kind of like the standard library; they become the patterns that allow people to leverage the low-level objects in new ways, where everyone doesn't need to learn how to bind to a raw TCP socket, interpret t... |
**Erik St. Martin:** Yeah, I'd agree with that. It's mostly abstraction layers on top to help facilitate tasks that you would want to accomplish with those lower-level objects. When you see a list of all these things it supports, it probably does look overwhelming, but like you said, they're just really workflow-type s... |
You guys are kind of trying to deprecate that for the replica set, right? |
**Kelsey Hightower:** Yeah, just a naming convention. Now that we're on the topic of objects in Kubernetes, it's very much like in Golang where there's core types inside of the Go standard language specification. But you're also able to crack types yourself, right? You can have a type that may be a collection of other ... |
You as a user or as a vendor, you can craft a new Kubernetes object type and send it to Kubernetes through the third party extensions or third party resources, and we will automatically take your type definition in some ways and we will automatically generate the API endpoints, storage in Etcd and the integration with ... |
The schema is up to you or the developer of the tool that will be observing these objects, but that will allow you to extend the system in ways that we haven't even imagined, but still feel first-class to people that are used to using Kubernetes and the core types. |
**Brian Ketelsen:** Now, if you were interested in spinning up your own Kubernetes cluster, fire up a web browser, go directly to Linode.com/gotime, get two months for free with the GoTime20 code, and you can start your own Kubernetes exploration using awesome Linode cloud servers. Eight data centers across the world, ... |
And you could go to Kelsey's Learn Kubernetes The Hard Way repository... What's the repo for that, Kelsey? |
**Kelsey Hightower:** It's kelseyhightower/KubernetesTheHardWay on GitHub. |
**Brian Ketelsen:** Yeah, that would be the pefect place to get your feet wet with Kubernetes - Linode and Kelsey Hightower together. |
**Carlisia Thompson:** \[00:23:47.20\\\] Kelsey, you were talking about something that the developers can do, and a lot of this is going over my head because for the last four years I've worked at companies of sort of mid-size, that had actually very good DevOps teams. As a developer, I always work closely with DevOps,... |
Of course, once you have containers, you have to manage them. Now, from a perspective of a developer, what should we be looking at? Because what I'm thinking is, "Well, what if my DevOps team is not using Kubernetes, and what if that's not available to me?" How do I explore this in a way that I can maybe integrate it w... |
**Kelsey Hightower:** I think that's a good question, and if you think about who's building these systems, they're mainly developers these days. I would like to see more ops people, and we do see them building features around it, but I think you're thinking about this world where the developers are now spending a lot m... |
As a developer, you may be less interested in deploying and managing a Kubernetes cluster. There are different roles on the team for that, and if you're in a position where you have a dedicated group of people who are using a hosted system, that's great. As a developer, what you kind of care about is "I have this appli... |
But in production, you have a lot more concerns than just starting and stopping an application. Who's going to collect the logs and push them to a central place? How do you express the need of "I want this application to run across multiple machines, multiple data centers." That particular set of requirements needs a h... |
\[00:27:54.03\\\] From history in general, the core principle, even if you're not using Kubernetes, your team is going to have to build something very similar. How do I decide which machine my application runs on? Well, if you have a DevOps team and depending on how they do things, they may be recording that decision i... |
So if you think about it, Kubernetes takes a DevOps team and rolls it into a system, and in return gives you the developer an API that you can use to express what your application needs to run in production. |
**Carlisia Thompson:** Very cool. I wanna go into this right now. \[laughs\] |
**Brian Ketelsen:** One of the things that I think the concepts behind Docker and Kubernetes bring, even if you don't use them, is the DevOps world and the Twelve-Factor application ideas are so important even if you're not using containers, but you get so much more benefit from them when you are. When you inject your ... |
Those are the kind of things that I think are complementary in the container and orchestration world, that we should be doing regardless. |
**Carlisia Thompson:** Brian, how do we get the Twelve-Factor implementation of those ideas, facilitated by using something like Kubernetes? |
**Erik St. Martin:** As an example, if you have a token that needs to be exchanged between two services or you wanna verify a TLS certificate, if they are passed into your application through an environment variable, then what happens is when you create your pod specification, your pod manifest to give to Kubernetes, y... |
**Kelsey Hightower:** I wanna interrupt there... Kubernetes doesn't really care about Twelve-Factor at all. If you have a set of data that you wanna consume, a synchronous object in Kubernetes can be stored into a file that you name and will be injected into your container at runtime, or you can prefer to put them into... |
\[00:31:43.22\\\] To Brian's point, a distributed system like Kubernetes, which has the liberty to reschedule your application in the face of failures automatically for you - a node were to die, or say you have three nodes, and you have your application running, and you say "I would like three copies of my application ... |
If one of those servers were to die, you don't need to change anything. We will automatically move that third instance to one of the other nodes that have room to run your application. Now, the fact that his will happen in the automatic fashion is in your best bet or benefit to adhere to some of the things around Twelv... |
If your application is looking for a specific file on a specific server, you're going to run into trouble and you're gonna be unable to benefit from Kubernetes' ability to move you to another machine. |
This is why in Kubernetes when you have a token or a database username or password, you have the option of taking that secret that you or the DevOps team can define as key/value pairs in Kubernetes, but you as a developer - we talked about that API... The API also extends it to like a YAML file, if you like to think of... |
Kubernetes will do that automatically. It will make a callout to the API server runtime, pull in that secret, write it to a temporary file, inject it into your process. When you process starts, it will just see a file like it has always been, but we still stay true to the Twelve-Factor way of doing things. We don't wri... |
So in some ways, Twelve-Factor really was talking about a system with a few limited capabilities. It comes from the Heroku camp, and Heroku was a great system for moving us forward into giving people constraints and a contract. In Kubernetes we almost give you a few more contracts to let you have a little bit more flex... |
**Erik St. Martin:** The interesting thing about injecting configuration config maps or secrets into a pod as a file - there's some trickery because it's not actually that file that changes, but you can still watch the file system for changes to realize that your config has changed, that somebody within the cluster has... |
**Kelsey Hightower:** That's right. |
**Erik St. Martin:** This is kind of what Kelsey's bringing home... You can build applications the way you typically will as long as you're not coupling yourselves too much. I think people get a lot of the fear of missing out. Kubernetes is just wickedly cool, it does a lot of stuff for you, but not everybody needs it ... |
**Kelsey Hightower:** \[00:36:10.15\\\] And on that note as well, it's just like goroutines - you can go a long way in Golang without ever touching goroutines. If you're building a web app, the goroutines that are being used by net/http are kind of hidden from you in many ways, but you can go really far. Some people ab... |
I think over time, even though most people would say if you look at Kubernetes, it is kind of overkill, it is a lot of overhead, but I think the entire industry will rebase to expect "My app should be able to run in multiple data centers and have tooling that allows it to stay available", because all customers now just... |
**Erik St. Martin:** Yeah, I think that's fair. People have become accustomed to this whole five nines uptime. They kind of expect it out of every site, and completely lose their minds anytime their mobile app doesn't connect right away. |
There's a lot of services too, so I say that the maintenance of Kubernetes comes at a cost too, but a lot of people aren't maintaining their own Kubernetes clusters either; they're using public services that offer Kubernetes. GKE and CoreOS has an offering, and there was somebody else that I remember has a Kubernetes o... |
**Brian Ketelsen:** Speaking of GKE, how about the blog post that was just released about Pokémon GO? Have you read that yet Kelsey? |
**Kelsey Hightower:** Oh, you know I read that, man! \[laughter\] I live that! Our Google SRE team is amazing, and they represent why... You know, there's really no such thing as no ops. Even though the teams behind Pokémon GO... You know, they have their ops people as well, they interface with our ops people, but they... |
So that was a big win for the entire Kubernetes community, because Google doesn't build Kubernetes by itself, just like Golang; there are tons of contributors. And with any new system, especially around infrastructure tools, it isn't real until it's in production and people really are sending production and meaningful ... |
A game like Pokémon GO, that was used worldwide, globally, and it was a big sensation for a lot of people that were playing the game, it had revenue attached to it, so it became a very business critical situation that it ran well, and it was really nice to see Kubernetes shine in real life, in real workloads. |
**Brian Ketelsen:** Yeah, there are articles about that. We will put that in the show notes, it's a really impressive read. I'm curious... One of the things that when we talked about having you on the show - you said if you had a free weekend to hack on something, you would wanna hack on self-deploying Go applications.... |
**Kelsey Hightower:** \[00:40:07.19\\\] I actually did that weekend like two weekends ago when I was in New York. I was thinking about Kubernetes and all these platforms as a service tools, and the thing that made Go awesome to me, regardless of the syntax, the features or the standard library, was this idea that you c... |
And to think about it, now when we move on to Kubernetes and then we turn back and say, "You have to create all of these YAML files, you had to learn what goes in those YAML files...", we feel like we're back in that world of "Alright, now you wanna do a deployment, you have to do all of these steps to get there." I bu... |
What I've done in my prototype - it was actually on GitHub - is called "Hello, Universe." "Hello, world" is old school. "Hello, Universe" is the whole thing, right? So "Hello, Universe", when it launches this stuff onto Kubernetes, using the API, I go find all of my pod instances that are running, I attach their STDOUT... |
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