Kubernetes Client Lambda

• What is Kubernetes Client Lambda?
  • InCluster & OutOfCluster example
  • Watch example
  • Mock example
• How to get it?
• Why Kubernetes Client Lambda is better?
• Supported Lambda Function Type
• Primitive Pipeline Type

What is Kubernetes Client Lambda?

Kubernetes Client Lambda (KCL) is a wrapper library over kubernetes/client-go which provides light-weight lambda-styled streamized kubernetes resource manipulation interface. This project is basically inspired by Groovy style lambda, and is aiming at reducing the coding-overhead when referencing too many struct / interface provided by kubernetes/client-go. The only dependency of this project is kubernetes/client-go, so this project can be pure and light-weight for you. Currently KCL only provides support for those common-used resources like Pod / Service.. Click to see all the supported resources in KCL.

Note that: KCL can be compatible with any kubernetes version, because KCL is a wrapping over client-go and client-go will provide it

Also, KCL defines more useful primitive operation type beyond those provided, e.g. Create-If-Not-Exist, Update-Or-Create, Delete-If-Exist.., which can help you make your code more clean. These primitive operation is always at the end of streaming and consumes all the remaining element and apply operation on every element.

Basically, KCL is implemented by golang reflect and golang native facilities. KCL defines various resources provided by kubernetes as enumeratoin which hides some unneccessary details like API-version. Sometimes, managing these details can be painful for kubernetes developers. Meanwhile, I find it costs time when mocking kubernetes resources in static unit test, so KCL provides a very simple mocking for kubernetes resources which is implemented via map.

With KCL, you can operate kubernetes resources like this example:

// See doc for more info about lambda functions Grep / Map..
import kubernetes "github.com/yue9944882/kubernetes-client-lambda"

// In-Cluster example
kubernetes.InCluster().Type(kubernetes.ReplicaSet).InNamespace("test").NamePrefix("foo-").Map(func(rs *api_ext_v1.ReplicaSet) rs*api_ext_v1.ReplicaSet {
    // Edit in-place or clone a new one
    rs.Meta.Labels["foo-label1"] = "test" 
    return rs
}).Update()


// Out-Of-Cluster example
kubernetes.Pod.OutOfClusterDefault().InNamespace("devops").NameEqual("test-pod").Each(
    func(pod *api_v1.Pod) {
        count++
    },
)

As the following example is shown, Calling Mock() on Kubernetes Type Enumeration will create the expected mocking resources for you:

import kubernetes "github.com/yue9944882/kubernetes-client-lambda"

kubernetes.Mock().Type(kubernetes.ReplicaSet).InNamespace("test").Add(
    // An anonymous function simply returns a pointer to kubernetes resource 
    // Returned objects will be added to stream
    func(){
        rs.Name = "foo"
        rs.Namespace = "test"
        return &rs
    },
).Create()

// For non-namespace resources, leave namespace to "" in InNamespace call
kubernetes.Mock().Type(kubernetes.Namespace).InNamespace("").Add(
    // An anonymous function simply returns a pointer to kubernetes resource 
    // Returned objects will be added to stream
    func(){
        ns.Name = "devops"
        return &ns
    },
).Create()

Also watching the changes can be easier via KCL's wrapping of client-go's informer. You don't have to directly access events from client-go, instead, registering / unregistering closure to KCL's API:

import kubernetes "github.com/yue9944882/kubernetes-client-lambda"
import "k8s.io/apimachinery/pkg/watch"

var kcl KubernetesClientLambda = kubernetes.InCluster()
// kcl = kubernetes.Mock()

kcl.Type(kubernetes.ReplicaSet).WatchNamespace("default").Register(watch.Added, func(rs *api_v1.ReplicaSet){
    fmt.Println(rs.Name)
})

How to Get it?

go get github.com/yue9944882/kubernetes-client-lambda

Why Kubernetes Client Lambda is better?

• Manipulating kubernetes resources in one line
• Lambda-styled kubernetes resource processing.
• Watch resource event by registering a "Function" lambda
• Pipelined and streamlized.
• Light-weight and only depends on kubernetes/client-go
• User-friendly mocking kubernetes static interface

Checkout more examples under example folder.

Supported Lambda Function Type

First we have following types of lambda function:

(KR denotes Kubernetes Resources, a pointer to resouce, e.g. *api_v1.Pod, *api_ext_v1.ReplicaSet..)

Primitive Lambda Type

Name	Parameter Type	Return Type
Function	KR	-
Consumer	KR	KR
Predicate	KR	bool
Producer	-	KR

Kubernetes Resource Lambda Snippet

Name	Pipelinable	Description
NameEqual	yes	Filter out resources if its name mismatches
NamePrefix	yes	Filter out resources if its name doesn't have the prefix
NameRegex	yes	Filter out resources if its name doesn't match the regular expression
HasAnnotation	yes	Filter out resources if it doesn't have the annotation
HasAnnotationKey	yes	Filter out resources if it doesn't have the annotation key
HasLabel	yes	Filter out resources if it doesn't have the label
HasLabelKey	yes	Filter out resources if it doesn't have the label key

And these lambda can be consumed by following function:

Primitive Pipeline Type

Name	Pipelinable	Lambda Type	Description
Collect	yes	-	Deep copies the elements and put them into collection
Add	yes	Producer	Add the element returned by lambda into collection
Map	yes	Consumer	Add all the elements returned by lambda to a new collection
Grep	yes	Predicate	Remove the element from collection if applied lambda returned a false
First	yes	Predicate	Take only the first element when applied lambda returned a true
Iter	no	Function	Apply the lambda to every elements in the collection

Primitive methods like CreateIfNotExist, DeleteIfExist have no parameter and just consumes all elements at the end of the pipelining. Here are supported primitive kubernetes operation functions below:

Basic Operation

Operation	Param	Return1	Return2
Each	Function	lambda error	-
Any	Predicate	bool	lambda error
Every	Predicate	bool	lambda error
NotEmpty	-	bool	lambda error

Kubernetes Operation

Operation	Param	Return1	Return2
Create	-	bool(sucess)	lambda error
CreateIfNotExists	-	bool(success)	lambda error
Delete	-	bool(sucess)	lambda error
DeleteIfExists	-	bool(success)	lambda error
Update	-	bool(sucess)	lambda error
UpdateIfExists	-	bool(success)	lambda error
UpdateOrCreate	-	bool(success)	lambda error