chore: reorder the sections
Rémy-Christophe Schermesser
5 years ago
parent
baeb323ee2
commit
89af75173a
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apiVersion: apps/v1
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kind: StatefulSet
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metadata:
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name: web
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spec:
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selector:
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matchLabels:
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app: nginx # has to match .spec.template.metadata.labels
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serviceName: "nginx"
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replicas: 3
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template:
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metadata:
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labels:
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app: nginx # has to match .spec.selector.matchLabels
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spec:
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containers:
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- name: nginx
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image: k8s.gcr.io/nginx-slim:0.8
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ports:
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- containerPort: 80
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name: web
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volumeMounts:
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- name: www
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mountPath: /usr/share/nginx/html
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volumeClaimTemplates:
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- metadata:
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name: www
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spec:
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accessModes: [ "ReadWriteOnce" ]
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resources:
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requests:
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storage: 1Gi
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@ -0,0 +1,100 @@
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# Other topics
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## Introduction
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In this section you will get an overview of others k8s useful features, in order of complexity.
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## Namespace
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`Namespaces` is the way to support multiple virtual clusters in k8s.
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They are intended for use in environments with many users spread across multiple teams, or projects. For clusters with a few to tens of users, you should not need to create or think about `namespaces` at all. Start using `namespaces` when you need the features they provide.
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By default, all objects are in the `default` namespace. There is a "hidden" `namespace` where k8s runs services for itself.
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Try:
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```bash
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$ kubectl get namespace
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NAME STATUS AGE
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default Active 56d
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kube-public Active 56d
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kube-system Active 56d
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```
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```bash
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$ kubectl get all --namespace=kube-system
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[lot of stuff]
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```
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## `kubeval`
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It is a tool to validate your k8s YAML files: <https://github.com/garethr/kubeval>
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The easiest integration is with `docker run`, if you files are in the directory `kubernetes`
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```bash
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docker run -it -v `pwd`/kubernetes:/kubernetes garethr/kubeval kubernetes/**/*
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```
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## Helm
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It is a package manager for k8s: <https://helm.sh/>.
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It contains multiple, ready to use, k8s manifest for projects, for example [mysql](https://github.com/helm/charts/tree/master/stable/mysql)
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## Stateful Set
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Like a `Deployment`, a `StatefulSet` manages Pods that are based on an identical container spec. Unlike a `Deployment`, a `StatefulSet` maintains a sticky identity for each of their Pods. These pods are created from the same spec, but are not interchangeable: each has a persistent identifier that it maintains across any rescheduling.
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`StatefulSets` are valuable for applications that require one or more of the following.
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* Stable, unique network identifiers, ex: distributed system, like ElasticSearch
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* Stable, persistent storage, ex: MySQL
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* Ordered, graceful deployment and scaling
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* Ordered, automated rolling updates, ex: MySQL Master+Slave
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```yaml
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apiVersion: apps/v1
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kind: StatefulSet
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metadata:
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name: web
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spec:
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selector:
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matchLabels:
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app: nginx # has to match .spec.template.metadata.labels
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serviceName: "nginx"
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replicas: 3 # by default is 1
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template:
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metadata:
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labels:
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app: nginx # has to match .spec.selector.matchLabels
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spec:
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containers:
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- name: nginx
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image: k8s.gcr.io/nginx-slim:0.8
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ports:
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- containerPort: 80
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name: web
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volumeMounts:
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- name: www
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mountPath: /usr/share/nginx/html
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volumeClaimTemplates:
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- metadata:
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name: www
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spec:
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accessModes: [ "ReadWriteOnce" ]
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resources:
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requests:
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storage: 1Gi
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```
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## Exercises
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1. Install `helm`, and use it to install [`redis`](https://github.com/helm/charts/tree/master/stable/redis) in your minikube
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2. Configure a stateful set for nginx with a HPA at 1% CPU, in a namespace `staging`
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## Clean up
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```bash
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kubectl delete statefulset,deployment,service,pod --all
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```
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