kubeplay – a new way to interact with Kubernetes

NOTE: this project is still in an early stage

If you like this project, please checkout TODOs and open an issue if you'd like to contribute or discuss anything in particular.

Usage example: easy REPL with Ruby syntax

> ./kubeplay
kubeplay (namespace="*")> pods # list pods in the cluster
<list-of-pods>
kubeplay (namespace="*")> @pod = _.any # pick a random pod from the list
kubeplay (namespace="*")> puts @pod.to_json # output the pod definition in JSON
{
  "metadata": {
    ...
  },
  "spec": {
    ...
    "containers": [
      {
        ...
      }
    ],
  },
  "status": {
    ...
  }
}
kubeplay (namespace="*")> puts @pod.to_ruby # output the same as a Ruby hash
{ ... }
kubeplay (namespace="*")> @pod.delete! # I am a chaos monkey :)

Resource Verbs

Currently implemented verbs are the following:

• pods
• services
• replicasets
• daemonsets

Each of these can be used with index operator, e.g. services[10], as well as first, last and any methonds. Any resource object can be converted to a JSON string with to_json method, or a Ruby object with to_ruby.

With a Ruby object reprsentation you can do things like this:

@metadata = replicasets("*/").to_ruby.items.map do |k,v|
   v.metadata
end

@metadata.each do |i|
    puts "Name:\t#{i.name}"
    puts "Labels:\t#{i.labels}"
    puts
end

You can define a verb aliases with def_alias, e.g. to create an rs verb alias for replicasets use

def_alias :rs, :replicasets

By default a verb operates on all namespaces, hence (namespace="*") is shown in the prompt. You can switch current namespaces with namespace verb, e.g.

kubeplay (namespace="*")> namespace "kube-system"
kubeplay (namespace="kube-system")>

To go back to all-namespaces mode, use namespace "*".

Resource Arguments

A verb may take up two arguments in any order - a glob string and a block or hash.

TL;DR

To get all replica sets in default namespaces which have label app not matching foo or bar and label version matching 0.1 or 0.2 use

replicasets "default/", labels: -> { @app !~ %w(foo bar) ; @version =~ %w(0.1 0.2) ; }

To get all running pods with label app matching foo or bar use

pods { @app =~ %w(foo bar) ; status.phase == "Running" ; }

Glob Expressions

Here are some examples illustrating the types of glob expressions that kubeplay understands.

Get all pods in kube-systems namespace:

pods "kube-system/"

Get all pods in all namespace:

pods "*/"

Get all pods in current namespace with name matching *foo*:

pods "*foo*"

More specifically, this enables getting pods in a namespace other then current like this:

kubeplay (namespace="default")> pods "kube-system/foo-*"

Or, gettin pods with name matching "bar-* in all namespace like this:

kubeplay (namespace="default")> pods "*/bar-*"

NOTE: if current namespace is "*", pods "*" is the same as pods; pods "*/*" is always the same as pods "*/".

Label & Field Selectors

Another argument a resource verb understand is a block specifying label and field selectors using special syntax outlined below.

Label Selector Syntax

To match a label agains a set of values, use label("name") =~ %w(foo bar), or !~.

If you want to just get resources with a certain label to set anything, use label("baz").defined?

This

{
  label("name") =~ %w(foo bar)
  label("baz").defined?
}

will compile a selector string name in (foo, bar),myapp.

And this

{
  label("name") !~ %w(foo bar)
  label("baz").defined?
}

will compile a selector string name notin (foo, bar),myapp.

Some well-known labels have shortuct, e.g.

{
  @app !~ %w(foo bar)
  @version =~ %w(0.1 0.2)
  @tier =~ %w(frontend backend)
}

Simply pass a block like this:

replicasets { @app !~ %w(foo bar); @version =~ %w(0.1 0.2); @tier =~ %w(frontend backend); }

You can also use make_label_selector verb to construct these expressions and save those to variabels etc.

Field Selector Syntax

This syntax is different, yet somewhat simpler.

Here is a selector mathing all running pods:

{ status.phase != :Running }

Using Slectors

To get all running pods with label tier mathcing backend:

pods { status.phase != :Running ; @tier =~ "backend" ; }

Alternatively, if you prefer to be more explicit, you can use a hash:

pods fields: -> { status.phase != :Running }, labels: -> { @tier =~ "backend" }

You can also use compose selector expressions diretly as strings, if you prefer:

pods fields: "status.phase != Running", labels: "tier in (backend)"

Inspecting the Logs

To get grep logs for any pod matching given selector

pods{ @name =~ "launch-generator" ; }.any.logs.grep ".*INFO:.*", ".*user-agent:.*"

Usage example: object generator with minimal input

> ./kubeplay -kubeconfig ~/.kube/config
kubeplay (namespace="*")> @pod = make_pod(image: "errordeveloper/foo:latest")
kubeplay (namespace="*")> puts _.to_json
{
  "metadata": {
    "creationTimestamp": null,
    "labels": {
      "name": "foo"
    }
  },
  "spec": {
    "containers": [
      {
        "name": "foo",
        "image": "errordeveloper/foo:latest",
        "resources": {}
      }
    ]
  },
  "status": {}
}
kubeplay (namespace="*")> @pod.create!
kubeplay (namespace="*")> @pod.delete!

kubeplay (namespace="*")> ^D
>

TODOs

Here are some TODO items and ideas.

• pod.delete!
• pod.create!
• pod.logs & pod.logs.grep
• pods.logs & pods.logs.grep
• pod.logs.pager and pod.logs.grep.pager
• grep logs in any set of resources
• more fluent behaviour of set resources, e.g. replicasets.pods and not replicasets.any.pods
• reverse lookup, e.g. given @rs = replicasets.any, @rs.pods.any.owner should be the same as @rs
• way to run scripts and not just REPL
• extend resource generator functionality
  • ReplicaSet+Service
  • Kubefile DSL

Ideas

• simple framework for controllers and 3rd-party resource (e.g. chaos monkey of sorts, or use terraform to create an exteranl resource and store URL in a secret, custom policy controller made easy)
• multi-cluster support
• resource diff
• network policy tester framework
• eval/exec code in a pod
• test framework for apps, e.g. "Here is my app, it has a configmap and a secrete, and I want to test if it works"

Building

Get the source code and build the dependencies:

go get github.com/Masterminds/glide
go get -d github.com/errordeveloper/kubeplay
cd $GOPATH/src/github.com/errordeveloper/kubeplay
$GOPATH/bin/glide up -v
make -C vendor/github.com/mitchellh/go-mruby libmruby.a
go install ./rubykube

Build kubeplay:

go build .

Credits

The mruby integration was inspired by @erikh's box, and some of the code was initially copied from there.