kylemcc / kube-gen

Generate files from Kubernetes events

kube-gen

kube-gen is a template rendering tool that generates files and executes commands based on Kubernetes events and metadata.

Installation

Binary Download

See the Releases page

Docker Container

kube-gen can be run as a standalone container, or bundled in a container with other applications.

Images are available on Dockerhub:

$ docker run kylemcc/kube-gen ...

Or Github Package Registry:

$ docker run ghcr.io/kylemcc/kube-gen/kube-gen ...

Usage

When run with no arguments (or with -h/-help), kube-gen prints the following usage message.

$ kube-gen
Usage: kube-gen [options] <template> [<output>]

Render templates using Kubernetes metadata and events

Options:
  -host string
        If not set will use kubeconfig. If using proxy - set it to http://localhost:8001
  -interval int

  -kubeconfig string
        (optional) absolute path to the kubeconfig file (default "/Users/kyle/.kube/config")
  -log-cmd
        log the output of the pre/post commands (default true)
  -overwrite
        overwrite the output file if it exists (default true)
  -post-cmd string
        command to run after template generation in complete
  -pre-cmd string
        command to run before template generation
  -quiet
        when set to true, nothing is logged
  -type value
        types of resources to pull [pods, services, endpoints] - May be specified multiple times. If not specified, all types will be returned
  -version
        display version information
  -wait string
        <minimum>[:<maximum>] - the minimum and optional maximum time to wait after an event fires.E.g.: 500ms:5s
  -watch
        watch for new events

Arguments:
  template: path or URL of the template file to render, or - to read from STDIN
  output: (Optional) path to write the rendered content. If not specified,
          rendered content is printed to STDOUT. By default, this file will
          be overwritten if it exists. Use -overwrite=false to return an
          error instead

Authentication / Connecting to the Kubernetes API

By default, kube-gen will look for a kubeconfig file at $HOME/.kube/config. A different kubeconfig file may be specified by using the -kubeconfig flag. Alternatively, kube-gen provides a -host flag that, if set, will supersede the -kubeconfig. The -host flag is best paired with kubectl proxy, which listens on 127.0.0.1:8001 by default. The -host flag may also be set to the value of kube-apiserver's --insecure-bind-address / --insecure-port.

Watching for changes

The -watch flag configures kube-gen to watch the API for changes to Services, Pods, and Endpoints (support for other types is forthcoming). This mode is useul when combined with the -pre-cmd, -post-cmd, and -wait parameters.

Template Language

kube-gen supports templates written in Go`s text/template language. It supports all of the built in functions, as well as numerous custom functions described below. Many of the custom functions (and the documentation for those functions) have been borrowed from docker-gen. Those functions, along with the accompanying License and Copyright are located in the dockergen_template_functions.go source file.

kube-gen's Issues

[dependency] Upgrade kubernetes client

The kubernetes client is getting pretty ancient, and should be upgraded to a modern version.

https://github.com/kubernetes/client-go

Current version is

https://github.com/kylemcc/kube-gen/blob/16e1462f32d6feb6419dacfdaa52789188de2cd6/go.mod#L9C26-L10C1

from

https://github.com/kubernetes/client-go/releases/tag/v0.24.2

[question] Can `kube-gen` be restricted to a namespace?

Currently it seems that kube-gen requires a ClusterRole in order to work. It appears that there aren't any controls for limiting the scope of kube-gen to a specific namespace.

For our use case, we want to run https://github.com/kylemcc/kube-nginx-proxy in certain namespaces, and only generate nginx configurations for services / pods within the same namespace. In this scenario, we would also want to only use namespace scoped roles, not cluster scoped roles.

Is this currently possible? Maybe using environment variables or undocumented flags?

[feature] Add Sprig to the template processor

There may be underlying reasons why this wasn't included at some point, but seeing as the Sprig library is pretty well maintained, it would make sense to include it with the kube-gen template processor.

https://github.com/Masterminds/sprig

I think it only requires adding the following here

kube-gen/template_funcs.go

Line 3 in 5534ca5

import (

:

import (
  "github.com/Masterminds/sprig/v3"
  "html/template"
)

and merging these functions here

kube-gen/template_funcs.go

Line 17 in 5534ca5

var Funcs = template.FuncMap{

:

tpl := template.Must(
  template.New("base").Funcs(sprig.FuncMap()).ParseGlob("*.html")
)

Working Example

Hi ,

Thanks for the awesome job ! This is very useful.

Can you please provide some working example of templates ? How to uses functions and stuff , how to get annotation from ingress for example.

That would be very useful !

Thanks