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Kubernetes in about 45 minutes
Everything you need to know to be dangerous
Philip LombardiPlatform Engineer
datawire.io
Who is this Phil Lombardi guy?
Twitter: @TheBigLombowski
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Why are we all here?
● You are curious about Kubernetes (and friends) and want a primer!
● You are invested in Kubernetes but are looking to learn about some techniques and tools to make your developers lives better.
● This is the last preso and you feel guilty about leaving early :)
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Agenda...
● Part 1: Containers and Docker and Kubernetes, Oh my!
● Part 2: Kubernetes Core Concepts
● Part 3: Development Workflow
● Part 4: Logging, Debugging and Resiliency
● Q & A
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Lesson 1: Containers and Docker and Kubernetes, Oh my!
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What is a container?
● Lightweight Linux environment. It is a form of virtualization… but very different from a full virtual machine.
● Immutable, deployable artifact.
● Runnable.
● Popularized by Docker but there are many implementations (e.g. LXC, Rkt).
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What is Docker?
● A tool, ecosystem and platform for building, pushing and running containers.
● The most popular container runtime currently.
● Default container runtime in Kubernetes.
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Why Containers?
● Easy and fast to produce.
● Great way to isolate different components in a complex system.
● Ensures a reproducible runtime for your app along the dev -> build -> test -> prod pipeline.
● Easy to share in a team or with external partners.
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What is Kubernetes?
● Runs massive numbers of containers based on lessons learned by Google.
● Schedules and runs all kinds of containers○ long-lived (e.g. services)○ short-lived (e.g. pre-launch hooks, cronjobs etc)
● Kubernetes can be thought of as a Distributed OS or process manager
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The Office Tower Analogy
Your product is the buildingas a whole.
Your business logic is
the offices and workers
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The Office Tower Analogy
Kubernetes provides the infrastructure to build your app around.
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It is the foundational app platform for your team to build your businesses apps around.
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Why Kubernetes?
It is not the only kid in the neighborhood…
● Amazon ECS
● Docker Swarm
● Hashicorp Nomad
● Apache Mesos
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Why Kubernetes?
Three big reasons to use Kubernetes over the other solutions:
1. Biggest ecosystem of the bunch and there is a hugely massive community
2. Runnable just about anywhere: cloud, bare-metal, and engineers laptops.
3. Unprecedented cloud portability.
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Kubernetes Architecture
Types of nodes: Masters and Workers
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Docker Kubelet
Kubeproxy
Kubernetes Node
Docker Kubelet
Kubeproxy
Kubernetes Node
Docker Kubelet
Kubeproxy
Kubernetes Node
Etcd API Server
Controller Manager
Kubernetes Master
Scheduler
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Lesson 2: Core Kubernetes Concepts
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The “Big Five” of Kubernetes Concepts
● Pods
● Deployments
● Services
● ConfigMaps
● Secrets
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A Pod you say?
● One or more strongly-related containers…
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Story Server
name: blog
Redis
Comment Server
Frontend
host: kube-worker-0
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A Pod you say?
● Containers in a pod share the same host, pod IP and port space.
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IP: 100.124.71.175Story
Server
name: blog
Redis
Comment Server
Frontend
host: kube-worker-0
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A Pod you say?
● Unit of scaling is a Pod
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IP: 100.124.71.175
blog-0
kube-worker-0
IP: 100.124.71.176
blog-1
kube-worker-1
Kubernetes cluster
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Pods Summary
● Like a host. All containers inside of a pod are run on the same underlying worker machine.○ Can therefore reference localhost
○ … or share the filesystem
○ … or use unix domain sockets
● All containers in a Pod share the same IP and port space.
● Pods are not durable.
● Pods are a very low-level primitive construct. Necessary to know, but not commonly used directly.
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Deployments
● Simple mechanism to configure, scale and update applications.
● Kubernetes does the rest of the hard work of scheduling the Pods across the cluster to meet desired capacity numbers.
● Works like a thermostat… Ensures the current state is always consistent with the desired state.
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Services
● Services are stable “names” in Kubernetes that enable you to route traffic to Pods across the entire cluster.
● Every service gets its own IP address.
● Services route traffic to pods by matching labels.
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Services Illustrated
How to talk to both apps despite different IP addresses?
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IP: 100.124.71.175
blog-0
kube-worker-0
IP: 100.124.71.176
blog-1
kube-worker-1
Kubernetes cluster
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Services Illustrated
Add a Service which becomes a DNS A record pointing the pod IP addresses
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IP: 100.124.71.175
blog-0
kube-worker-0
IP: 100.124.71.176
blog-1
kube-worker-1
Kubernetes cluster
blog DNS (short) => blogDNS (long) => blog.default.cluster.local
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Services Illustrated
You can have multiple services target pods using labels and selectors.
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app=blogenv=prod
blog-0
kube-worker-0
app=blogenv=prod
blog-1
kube-worker-1
Kubernetes cluster
blog blog-staging
app=blog
blog-0
kube-worker-1
app=blogenv=prod
app=blog
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Service Flavors
● Many different flavors of “Service” in Kubernetes
○ ClusterIP
○ NodePort
○ LoadBalancer
○ ExternalName - often forgotten, but very useful!
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Services Summary
● Creates DNS A records pointing at Pod IP addresses
● Powerful label matching capabilities that enable you to route traffic to particular pods (e.g. for blue-green or canary releases).
● Supports DNS SRV records so you can avoid hard coding port numbers in your app code as well.
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ConfigMap
● Containers are immutable… so how do you provide runtime configuration to them?
● Age old question for immutable infrastructure lots of good (and bad) solutions have been built over the years.
● Kubernetes solution is built-in as the ConfigMap. Inject configuration information as…○ Environment variables
○ Volumes
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Secret
● Cousin of the ConfigMap
● Operates almost exactly the same as a ConfigMap but designed for storing sensitive information.
● Secret information only sent from master to worker nodes when needed by a pod. The data lives in memory so it is not on the disk.
● One important aspect of secrets… the master currently stores them in plaintext. Work in Progress to eliminate this in the future, but worth being aware of.
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Kubernetes to AWS
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Kubernetes AWS
Pod EC2 Instance
Deployment AutoScaling Group + Launch Configuration
Service ELB
ConfigMap N/A
Secret N/A
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Lesson 3: Developer Workflow
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Developers...
● Part of our role involves aiding Developers and making them faster and more productive.
● Kubernetes is awesome and it comes with a lot of power.
● Great power comes with lots of potential for learning pain.
● How do we make developers productive?
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Manifests
● A declarative YAML/JSON config format that describe at a high level how Kubernetes should operate.
● Kubernetes operates like a thermostat. Transforms current state -> desired state based on config in the Manifest.
● Manifests often need to be parameterized (e.g. to change the container image). General approach is to use some kind of templating.
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Structuring an Application
● Often asked, all this stuff is cool, but how should we structure our apps to be consistent and compatible with tooling?
● Strongly recommend a k8s/ directory in the top of your project
○ Manifests can be concrete and ready to use by just running `kubectl apply -f k8s/ `
○ … or you can take an alternate approach and put templates in that directory and do some kind of config generation with say Python + Jinja2 (for example).
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Writing Manifests
● Avoid hard coding environment configuration into manifests.○ Templating
○ Kubectl switches (e.g. for namespaces)
● Stick to YAML even if Kubernetes supports JSON… not uncommon to want comments in the manifests.
● Kubernetes manifests can be spread across multiple files or kept in a single file. Strongly recommend using a single file until it becomes bothersome to maintain.
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Development Workflows
● No single workflow that works for all developers or teams
● Need tools that can adapt to changing requirements and process
● Personally, great success with:○ Trunk-based development model.
○ Using parameterized templates in k8s/ directory.
○ monorepo or “pseudo-monorepo”.
○ Dev-tooling the focuses on speed and maintaining fast iteration cycles
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Forge (https://forge.sh)
● Build and deploy Kubernetes-based microservices quickly.
● Can deploy 1 or 100 services from source to Kubernetes in seconds.
● Changes are applied incrementally. Computes the diff of a change and then pushes the update to Kubernetes.
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Lesson 4: Logging, Debugging and Resiliency
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Logging...
● Kubernetes has a built-in log aggregation but it is limited (STDOUT, STDERR only).
● `kubectl logs` is good enough for devs but invest in a real logging solution for prod.
● You will want something like fluentd and elasticsearch because Kubernetes does not track historical logs for crashed or terminated pods.
○ Also search capabilities are limited to how much of a grep wizard you are.
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Logging...
● There is more to logging than just application logs.
● Consider introducing a service mesh to your cluster that allows you to do per-request logging and tracing.
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Services Mesh
● This was covered in a presentation yesterday so here is the recap:
A dedicated infrastructure layer for making service-to-service communication safe and reliable.
● Kubernetes and CNCF are really pushing Lyft Envoy as the mechanism to build a service mesh.
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Simple Log Query Tools
● Because the kubectl logs command is so limited many tools have been written to make it easier...
○ ktail https://github.com/atombender/ktail
○ kubetail https://github.com/johanhaleby/kubetail
○ stern https://github.com/wercker/stern
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Debugging...
Kubernetes IS complex. There are a lot of failure scenarios in all kinds of places. The Kubernetes docs are pretty helpful for doing some troubleshooting
Application Troubleshooting:
https://kubernetes.io/docs/tasks/debug-application-cluster/debug-application/
Cluster Troubleshooting:
https://kubernetes.io/docs/tasks/debug-application-cluster/debug-cluster/
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Debugging The Cool Way
● Sometimes you need something more powerful than logs…
● Or your developers use a shared development-staging cluster and something is broken...
● Classic problem with building web services… How do I attach a local process to the running cloud environment? What about a debugger?
● Super easy in Kubernetes with a tool called Telepresence!http://www.telepresence.io/
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● Telepresence proxies network requests, environment variables, and volumes to local Telepresence client
● Code locally on your laptop using your favorite editor and your local filesystem :)
Telepresence
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Wrapping Up
● Kubernetes is awesome!
● There’s a lot of power and flexibility
● We need to empower developers by providing them excellent tools that make their lives easier!
● As infrastructure and ops engineers we need to build a stable platform that developers can use without feeling restricted. The service mesh makes this easier.
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Preso Over! Thank you!
● If you’re building cloud applications on top of Kubernetes, check out our open source tools:
● Contact us @datawireio or [email protected]
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