Super practical! K8s developers must know the six open source tools

Source: Cloud native laboratory, Click to view the original .

REVIEW : Kubernetes as native cloud era "operating system", it is familiar with and use per user (User) essential skills. If you are working on Kubernetes, you need the right tools and techniques to ensure the stable operation of high availability and workload Kubernetes cluster. This article will give you details of six practical Kubernetes open source tools, do not miss.

Foreword

With the development and evolution Kubernetes, one can tame its excesses from within. But some people are not willing to become dry and so Kubernetes easy to use and develop their own solutions to many common questions have been put into production Kubernetes encountered.

Here we will introduce some techniques to improve operational efficiency, and to name a few of the more useful open source Kubernetes tools that simplify Kubernetes in various ways, including streamlining the command line interaction, simplify application deployment and grammar.

kubectl autocomplete

kubectl This command-line tool is very important, associated commands are also many, we can not remember so many commands, but also often wrong, so the auto-complete command is necessary, kubectl tool itself supports auto-fill full, simply set up what you can.

bash users

Most users are using a shell  bash, Linux system can be set by the following command:

$ echo "source <(kubectl completion bash)" >> ~/.bashrc
$ source ~/.bashrc

If you can not find auto-completion, you can try to install  bash-completion then refresh can!

zsh users

If you use a shell is the  zshcan be set by the following command:

$ echo "source <(kubectl completion zsh)" >> ~/.zshrc
$ source ~/.zshrc

Custom kubectl get output

kubectl get Related Resources, the default output is kubectl built, generally we can use  -o json or  -o yaml view the complete resource information. But many times, the information we need to be concerned not exhaustive, so we need to customize the output of the column, you can use  go-template to achieve.

go-template Golang is a template, you can refer to  the instructions of the template .

For example, only want to see the acquisition of pods in each pod is  uid, you can use the following command:

$ kubectl get pods --all-namespaces -o go-template='{{range .items}}{{.metadata.uid}}
{{end}}'
2ea418d4-533e-11e8-b722-005056a1bc83
7178b8bf-4e93-11e8-8175-005056a1bc83
a0341475-5338-11e8-b722-005056a1bc83
...

Because get pods of the result is  List the type of acquisition pods in  items this of value, and therefore need to traverse items, and will have  {{range .items}}. Then the selected content to be presented by the template, that is items each  {{.metadata.uid}}.

Special attention here to do a special deal, it is to  {{end}} the front line break, in order to insert a line break in the template.

Of course, if you feel that this treatment is not elegant, you can also use the  printf function, in which use  \n can be realized insert line breaks.

$ kubectl get pods --all-namespaces -o go-template --template='{{range .items}}{{printf "%s\n" .metadata.uid}}{{end}}'

Or it can be:

$ kubectl get pods --all-namespaces -o go-template --template='{{range .items}}{{.metadata.uid}}{{"\n"}}{{end}}'

With the fact  printf, you can easily achieve the output of the corresponding field, and can control their own style. For example, it can be:

$ kubectl get pods --all-namespaces -o go-template --template='{{range .items}}{{printf "|%-20s|%-50s|%-30s|\n" .metadata.namespace .metadata.name .metadata.uid}}{{end}}'
|default             |details-v1-64b86cd49-85vks                        |2e7a2a66-533e-11e8-b722-005056a1bc83|
|default             |productpage-v1-84f77f8747-7tkwb                   |2eb4e840-533e-11e8-b722-005056a1bc83|
|default             |ratings-v1-5f46655b57-qlrxp                       |2e89f981-533e-11e8-b722-005056a1bc83|
...

The following two go-template advanced usage examples:

• range nesting

# 列出所有容器使用的镜像名
$ kubectl get pods --all-namespaces -o go-template --template='{{range .items}}{{range .spec.containers}}{{printf "%s\n" .image}}{{end}}{{end}}'
istio/examples-bookinfo-details-v1:1.5.0
istio/examples-bookinfo-productpage-v1:1.5.0
istio/examples-bookinfo-ratings-v1:1.5.0
...

• Conditional

# 列出所有不可调度节点的节点名与 IP
$ kubectl get no -o go-template='{{range .items}}{{if .spec.unschedulable}}{{.metadata.name}} {{.spec.externalID}}{{"\n"}}{{end}}{{end}}'

In addition to use  go-template , you can also use a comma-separated list of columns to print custom forms:

$ kubectl -n kube-system get pods coredns-64b597b598-7547d -o custom-columns=NAME:.metadata.name,hostip:.status.hostIP
NAME                       hostip
coredns-64b597b598-7547d   192.168.123.250

You can also use  go-template-file a custom list of templates, the template parameter do not pass go, but written in a file, then you need to specify  template points to the file.

$ cat > test.tmpl << EOF 
NAME                      HOSTIP
metadata.name       status.hostIP
EOF
$ kubectl -n kube-system get pods coredns-64b597b598-7547d -o custom-columns-file=test.tmpl
NAME                       HOSTIP
coredns-64b597b598-7547d   192.168.123.250

Interactive Kubernetes client

Kube-prompt  allows you to enter the equivalent of what the client Kubernetes interactive command session and provides background information automatically populated for each command, you do not have to type the kubectl to add a prefix for each command.

Alias ​​generated kubectl

If you need to use kubectl and kubernetes api to interact frequently, using the alias will save you a lot of time, open source project  kubectl-aliases  can be generated programmatically kubectl alias, alias generation rule as follows:

• Alias ​​simple example

  kd → kubectl describe

• Senior alias example

  kgdepallw → kubectl get deployment --all-namespaces --watch

Check the configuration file

If you manually write Kubernetes manifest file, the syntax is very difficult to check the manifest file, especially when you have several different versions of Kubernetes cluster, confirm that the configuration file syntax is correct even more difficult.

Kubeval  is a tool to check Kubernetes YAML or JSON configuration file to support multiple versions Kubernetes that can help us solve a lot of trouble.

• Examples of Use

$ kubeval nginx.yaml
The document nginx.yaml contains an invalid Deployment
---> spec.replicas: Invalid type. Expected: integer, given: string

Simplify deployment defined Kubernetes

Many people have complained defined Kubernetes manifest file is too complex and lengthy. They are difficult to write and difficult to maintain, if we can simplify deployment definitions will greatly reduce maintenance difficulty.

Kedge  provide simpler, more concise syntax, and then convert it to kedge Kubernetes manifest file.

• Examples of Use

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