Helm -- a powerful package management tool for kubernetes applications

Catalog

Helm What is it? ？

Use helm The advantages of

Helm The overall architecture

​ edit Helm Main components

Helm Workflow

Helm edition

Helm Deployment installation

Construct a  Helm Chart

Helm Basic commands

---

Helm What is it? ？

Helm yes Deis One developed for Kubernetes Applied package management tools , Mainly used for management Charts. It's kind of like Ubuntu Medium APT or CentOS Medium YUM.

Helm Chart It's for encapsulation Kubernetes A series of native applications YAML file . You can customize some of the applications when you deploy them Metadata, To facilitate application distribution .

For app Publishers , Can pass Helm Package applications 、 Manage application dependencies 、 Manage the application version and release it to the software warehouse .

For users , Use Helm There is no need to write complex application deployment files , In a simple way Kubernetes Up lookup 、 install 、 upgrade 、 Roll back 、 Uninstall application .

Use helm The advantages of

Generally, the process of deploying an application ：

• To write yaml file ——》  establish service External exposure ——》  adopt ingress Domain access

  • There are many ways for external applications to access services in the cluster , I won't go into details here

Don't use helm

• Only suitable for simple applications . In fact, we deploy micro service projects , There could be dozens of services , It's not appropriate to use this way . A lot of... Needs to be maintained yaml file .

Use helm

• A large number of yaml Documents are managed as a whole
• Realization yaml Efficient reuse of files .
• Implement application level version management

Helm The overall architecture

Helm Main components

• Chart：Chart It's a Helm Software package , use tar Format . Includes running a K8S The image needed by the application 、 Dependency and resource definition, etc , That is, it contains a resource object required by an application YAML file .
• Repository（ Warehouse ）： yes Helm Software warehouse of ,Repository It's essentially a Web The server , The server holds a series of Chart Software package for users to download , And it provides the Repository Of Chart The manifest file of the package is easy to query .
• Config（ The configuration data ）： Set to on deployment Chart Configuration data in .
• Release： Use helm install Command in k8s Deployed in a cluster Chart be called Release . Is based on Chart and Config Deploy to K8S An instance running in the cluster . One Chart Can be deployed multiple times , Every time the Release Are different .

Helm Workflow

• Developers will develop good Chart Upload to Chart Warehouse .
• The operation and maintenance personnel are based on Chart The definition of , Set the necessary configuration data （Config）, Use Helm The command line tool deploys the application to K8S In the cluster , With Release Concept management, subsequent update rollback, etc .
• Chart Warehouse Chart Can be used to share and distribute .

Helm edition

• V2 edition Helm rely on Tiller Components .Tiller Component is used to receive Helm Instructions from the client , And K8S Of API Server Interaction , Complete the deployment and management of resource objects .
• V3 edition Helm No longer use Tiller Components , It's going to be API Server Integration of interactive functions into Helm In the client program .

Helm Deployment installation

because helm Package abroad , Download through this website in China ：

wget https://mirrors.huaweicloud.com/helm/v3.3.1/helm-v3.3.1-linux-amd64.tar.gz      

tar -zxvf helm-v3.3.1-linux-amd64.tar.gz

cp linux-amd64/helm /usr/local/bin/

helm version

notes : helm The client needs to be downloaded to the installation kubectl And it can be executed and passed normally kubectl operation kubernetes On , otherwise helm Will not be available

Construct a  Helm Chart

helm create mychart

This command creates a mychart Catalog , The directory structure is as follows .

[[email protected] ~]# tree mychart/
mychart/                             # Chart  Catalog 
├── charts                           #  This  charts  Other dependent  charts, Always installed 
├── Chart.yaml                       #  Describe this  Chart  Information about 、 Including the name 、 Description information 、 Version, etc 
├── templates                        #  The template directory 
│   ├── deployment.yaml              # deployment  Controller  Go  Template file 
│   ├── _helpers.tpl                 #  With  _  The starting file will not be deployed to  k8s  On , Can be used to customize general information 
│   ├── hpa.yaml                     # hpa  Template file 
│   ├── ingress.yaml                 # ingress  Template file 
│   ├── NOTES.txt                    # Chart  Some information after deployment to the cluster , for example ： How to use 、 List default values 
│   ├── serviceaccount.yaml          # serviceaccount  Of  Go  Template file 
│   ├── service.yaml                 # service  Of  Go  Template file 
│   └── tests                        #  test pod Catalog 
│       └── test-connection.yaml     #  test pod Of deployment file 
└── values.yaml                      #  The value file of the template , These values will be applied to  GO  Template generation deployment file 

Templates Under the table of contents YAML The default values of the file template are all in values.yaml The definition of , For example deployment.yaml Container image defined in .

image: "{
    { .Values.image.repository }}:{
    { .Values.image.tag }}"

Among them .Values.image.repository The value of is values.yaml The definition of nginx,.Values.image.tag The value is stable.

$ cat mychart/values.yaml|grep repository
repository: nginx

$ cat mychart/values.yaml|grep tag
tag: stable

The values of the above two variables are in  create chart  The default value generated automatically when , It can be modified according to the actual situation .

Helm Basic commands

Add warehouse address

because helm The warehouse you bring is the address of the overseas warehouse , Pull application is slow . You can see that many servers have been installed through alicloud image installation charts.

helm repo add  Repository name   The repository URL
helm repo update

 For example, add Alibaba cloud's warehouse address 
helm repo add repo_name1 https://aliacs-app-catalog.oss-cn-hangzhou.aliyuncs.com/charts-incubator/

 Because the warehouse is constantly updated , So it's best to use update Update 
helm repo update

 View the list of added warehouses 
helm repo list

Search by keyword chart package

$ helm search repo keyword
$ helm search hub keyword

above 2 The first command is only on the 3 The two fields are different ,repo Means to search in the warehouse added locally ;hub It means that Helm Hub Search in .

see helm package

$ helm inspect state/mysql

install helm

In the simplest case , It only needs one chart Name parameter of ：

$ helm install stable/mysql

 If you want to use your own release name   Using parameter  --name  that will do 

 Can pass  helm install --dry-run --debug  Command to debug 

View installed chart list

$ helm list

to update charts List for the latest version

helm repo update 

see chart Package file content

helm show chart chartName  #  see chart In bag  chart.yaml  The contents of the document 
# chart Packages can be local, unpackaged chart Catalog （ namely  helm create  created chart Catalog ）, It can also be packaged chart Compressed package （ from helm package pack ）, It can also be stored in the warehouse chart package 
 
helm show values chartName    #  see chart In bag values.yaml The contents of the document 

helm show readme chartName     # see chart In bag README The contents of the document 

helm show all chartName   #  see chart In bag chart.yaml、values.yaml、README The contents of the document 

uninstall release

$ helm uninstall releaseName

Parameters ：--keep-history( Adding this parameter will delete records )

upgrade release

$ helm upgrade releaseName chartName

Roll back release

$ helm rollback releaseName vision

vision Expressed as the version ,1 Indicates the first version ,2 Indicates the second version , And so on

see release Basic information of

$ helm status releaseName

of Helm That's all for a brief introduction ,helm It's a very powerful k8s Package management tools , If you want to know more, you can look at the official documents carefully , I hope this article can help you ！