{"id":1033,"date":"2020-09-14T18:07:54","date_gmt":"2020-09-14T18:07:54","guid":{"rendered":"https:\/\/blog.samarthya.me\/wps\/?p=1033"},"modified":"2020-09-15T06:53:41","modified_gmt":"2020-09-15T06:53:41","slug":"writing-charts","status":"publish","type":"post","link":"https:\/\/blog.samarthya.me\/wps\/2020\/09\/14\/writing-charts\/","title":{"rendered":"Writing Helm Charts"},"content":{"rendered":"\n

Helm is a dedicated package manager for Kubernetes.<\/p><\/blockquote><\/figure>\n\n\n\n

Although the Kubernetes<\/code> objects are deployed in YAML’s there was a need to package and club them together and customise the deployment (not the K8S deployment).<\/p>\n\n\n\n

Helm uses Go templates<\/code>. <\/p>\n\n\n\n

Please refer to official go documentation on template package for details. You can also look at examples in my repo here.<\/a><\/p><\/blockquote><\/figure>\n\n\n\n

Actions from the official documentation<\/p>\n\n\n\n

{{\/* a comment *\/}}\n{{- \/* a comment with white space trimmed from preceding and following text *\/ -}}\n\tA comment; discarded. May contain newlines.\n\tComments do not nest and must start and end at the\n\tdelimiters, as shown here.\n\n{{pipeline}}\n\tThe default textual representation (the same as would be\n\tprinted by fmt.Print) of the value of the pipeline is copied\n\tto the output.\n\n{{if pipeline}} T1 {{end}}\n\tIf the value of the pipeline is empty, no output is generated;\n\totherwise, T1 is executed. The empty values are false, 0, any\n\tnil pointer or interface value, and any array, slice, map, or\n\tstring of length zero.\n\tDot is unaffected.\n\n{{if pipeline}} T1 {{else}} T0 {{end}}\n\tIf the value of the pipeline is empty, T0 is executed;\n\totherwise, T1 is executed. Dot is unaffected.\n\n{{if pipeline}} T1 {{else if pipeline}} T0 {{end}}\n\tTo simplify the appearance of if-else chains, the else action\n\tof an if may include another if directly; the effect is exactly\n\tthe same as writing\n\t\t{{if pipeline}} T1 {{else}}{{if pipeline}} T0 {{end}}{{end}}\n\n{{range pipeline}} T1 {{end}}\n\tThe value of the pipeline must be an array, slice, map, or channel.\n\tIf the value of the pipeline has length zero, nothing is output;\n\totherwise, dot is set to the successive elements of the array,\n\tslice, or map and T1 is executed. If the value is a map and the\n\tkeys are of basic type with a defined order, the elements will be\n\tvisited in sorted key order.\n\n{{range pipeline}} T1 {{else}} T0 {{end}}\n\tThe value of the pipeline must be an array, slice, map, or channel.\n\tIf the value of the pipeline has length zero, dot is unaffected and\n\tT0 is executed; otherwise, dot is set to the successive elements\n\tof the array, slice, or map and T1 is executed.\n\n{{template \"name\"}}\n\tThe template with the specified name is executed with nil data.\n\n{{template \"name\" pipeline}}\n\tThe template with the specified name is executed with dot set\n\tto the value of the pipeline.\n\n{{block \"name\" pipeline}} T1 {{end}}\n\tA block is shorthand for defining a template\n\t\t{{define \"name\"}} T1 {{end}}\n\tand then executing it in place\n\t\t{{template \"name\" pipeline}}\n\tThe typical use is to define a set of root templates that are\n\tthen customized by redefining the block templates within.\n\n{{with pipeline}} T1 {{end}}\n\tIf the value of the pipeline is empty, no output is generated;\n\totherwise, dot is set to the value of the pipeline and T1 is\n\texecuted.\n\n{{with pipeline}} T1 {{else}} T0 {{end}}\n\tIf the value of the pipeline is empty, dot is unaffected and T0\n\tis executed; otherwise, dot is set to the value of the pipeline\n\tand T1 is executed.<\/code><\/pre>\n\n\n\n
Example<\/h2>\n\n\n\n
Let’s show a go template example before we move to the Helm<\/code><\/p>\n\n\n\n
\/\/ Letter a template for the automatic reply.\nconst Letter = `\nDear {{.Name}},\n{{\/* Check if the person identified by .Name attended the event. *\/}}\n{{if .Attended}}\nIt was a pleasure to meet you at the wedding.\n{{- else}}\n{{\/* Person identified by .Name did not attended the event. *\/}}\nIt is a shame you couldn't make it to the wedding.\n{{- end}}\n{{with .Gift -}}\nThank you for the lovely {{.}}.\n{{end}}\nBest wishes,\nJosie\n`\n\n\/\/ Recipient Identifies the recipient\ntype Recipient struct {\n\tName, Gift string\n\tAttended   bool\n}<\/code><\/pre>\n\n\n\n
If I need to evaluate this template which is nothing just a letter template that works on some values provided.<\/p>\n\n\n\n
Will use sample values for the struct Recipient as under<\/p>\n\n\n\n
var recipients = []two.Recipient{\n\t\t{\"Aunt Mildred\", \"bone china tea set\", true},\n\t\t{\"Uncle John\", \"moleskin pants\", false},\n\t\t{\"Cousin Rodney\", \"\", false},\n\t}<\/code><\/pre>\n\n\n\n
\/\/ exampleTwo - Uses the actions and pipelines\nfunc exampleTwo() {\n\tt := template.Must(template.New(\"letter\").Parse(two.Letter))\n\n\t\/\/ Execute the template for each recipient.\n\tfor _, r := range recipients {\n\t\terr := t.Execute(os.Stdout, r)\n\t\tif err != nil {\n\t\t\tlog.Println(\"executing template:\", err)\n\t\t}\n\t}\n}<\/code><\/pre>\n\n\n\n
Once invoked it will print on the console.<\/p>\n\n\n\n
Dear Aunt Mildred,\n\nIt was a pleasure to meet you at the wedding.\nThank you for the lovely bone china tea set.\n\nBest wishes,\nJosie\n<\/code><\/pre>\n\n\n\n
Dear Uncle John,\n\nIt is a shame you couldn't make it to the wedding.\nThank you for the lovely moleskin pants.\n\nBest wishes,\nJosie\n<\/code><\/pre>\n\n\n\n
Dear Cousin Rodney,\n\nIt is a shame you couldn't make it to the wedding.\n\nBest wishes,\nJosie\n<\/code><\/pre>\n\n\n\n
Local – helm<\/code> version<\/h2>\n\n\n\n
The local helm version I am using on my box – helm version<\/code><\/p>\n\n\n\n
version.BuildInfo{Version:\"v3.3.1\", GitCommit:\"249e5215cde0c3fa72e27eb7a30e8d55c9696144\", GitTreeState:\"dirty\", GoVersion:\"go1.15\"}<\/code><\/pre>\n\n\n\n
helm version --short\nv3.3.1+g249e521<\/code><\/pre>\n\n\n\n
Creating my chart<\/h3>\n\n\n\n
helm create epserver<\/code><\/pre>\n\n\n\n
It creates some files as mentioned below<\/p>\n\n\n\n
.\n\u251c\u2500\u2500 Chart.yaml\n\u251c\u2500\u2500 charts\n\u251c\u2500\u2500 templates\n\u2502   \u251c\u2500\u2500 NOTES.txt\n\u2502   \u251c\u2500\u2500 _helpers.tpl\n\u2502   \u251c\u2500\u2500 deployment.yaml\n\u2502   \u251c\u2500\u2500 hpa.yaml\n\u2502   \u251c\u2500\u2500 ingress.yaml\n\u2502   \u251c\u2500\u2500 service.yaml\n\u2502   \u251c\u2500\u2500 serviceaccount.yaml\n\u2502   \u2514\u2500\u2500 tests\n\u2502       \u2514\u2500\u2500 test-connection.yaml\n\u2514\u2500\u2500 values.yaml<\/code><\/pre>\n\n\n\n
I will give a brief about most of the file I edit, but you read more anytime from the official Helm documentation<\/p>\n\n\n\n
Chart.yaml<\/h4>\n\n\n\n
A YAML file containing information about the chart<\/p><\/blockquote><\/figure>\n\n\n\n
templates\/                                       [DIRECTORY]<\/h4>\n\n\n\n
A directory of templates that, when combined with values, will generate valid Kubernetes manifest files.<\/p><\/blockquote><\/figure>\n\n\n\n
values.yaml<\/h4>\n\n\n\n
The default configuration values for this chart<\/p><\/blockquote><\/figure>\n\n\n\n
charts\/                                 [DIRECTORY]<\/h4>\n\n\n\n
A directory containing any charts upon which this chart depends.<\/p><\/blockquote><\/figure>\n\n\n\n
Added some details in the Chart.yaml<\/code>, which are self explanatory<\/p>\n\n\n\n
# Minimum Version 3 required so v2\napiVersion: v2\nname: epserver\ndescription: A sample go server that exposes few endpoints.\ntype: application\nversion: 2.0.0\nkubeVersion: ~1.18.x\nappVersion: 3.0.0<\/code><\/pre>\n\n\n\n
serviceaccount.yaml<\/h4>\n\n\n\n
{{- if .Values.serviceAccount.create -}}\napiVersion: v1\nkind: ServiceAccount\nmetadata:\n  name: {{ include \"epserver.serviceAccountName\" . }}\n  labels:\n    {{- include \"epserver.labels\" . | nindent 4 }}\n  {{- with .Values.serviceAccount.annotations }}\n  annotations:\n    {{- toYaml . | nindent 4 }}\n  {{- end }}\n{{- end }}<\/code><\/pre>\n\n\n\n
I will use my application epserver<\/a><\/code> and create a chart for it just to check if simple modifications work. <\/p>\n\n\n\n
All, code is available in my github repo<\/a>.<\/p><\/blockquote>\n\n\n\n
Values.yaml<\/h4>\n\n\n\n
# Replica count\nreplicaCount: 1\n# Only 1 replica required\n\n# Labels for container\nappname: epserver\n\n# define the environment variable.\nenv:\n  defined: true\n  vars:\n    - name: SERVERPORT\n      value: \"9090\"\n\nimage:\n  repository: samarthya\/epserver\n  pullPolicy: Always\n  # Overrides the image tag whose default is the chart appVersion.\n  tag: \"2.0\"\n\nimagePullSecrets: []\nnameOverride: \"samarthya\"\nfullnameOverride: \"eps\"\n\n# Samarthya: Added v1\nenvironment: \"test\"\n\nserviceAccount:\n  # Specifies whether a service account should be created\n  create: true\n  # Annotations to add to the service account\n  annotations: {}\n  # The name of the service account to use.\n  # If not set and create is true, a name is generated using the fullname template\n  name: sa-epserver\n\npodAnnotations: {}\n\npodSecurityContext: {}\n  # fsGroup: 2000\n\nsecurityContext: {}\n  # capabilities:\n  #   drop:\n  #   - ALL\n  # readOnlyRootFilesystem: true\n  # runAsNonRoot: true\n  # runAsUser: 1000\n\nservice:\n  type: ClusterIP\n  port: 9090\n\ningress:\n  enabled: false\n  annotations: {}\n    # kubernetes.io\/ingress.class: nginx\n    # kubernetes.io\/tls-acme: \"true\"\n  hosts:\n    - host: chart-example.local\n      paths: []\n  tls: []\n  #  - secretName: chart-example-tls\n  #    hosts:\n  #      - chart-example.local\n\nresources:\n# define limits\n  limits:\n    memory: \"250Mi\"\n    cpu: \"2000m\"\n\nautoscaling:\n  enabled: false\n  minReplicas: 1\n  maxReplicas: 100\n  targetCPUUtilizationPercentage: 80\n  # targetMemoryUtilizationPercentage: 80\n\nnodeSelector: {}\n\ntolerations: []\n\naffinity: {}<\/code><\/pre>\n\n\n\n
Can you spot the changes done?<\/p>\n\n\n\n
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