Kubernetes Axios Informer

An informer implementation based on axios for @kubernetes/client-node.

Purpose

We found the following issues with current informer implementation of @kubernetes/client-node(v0.14.0):

• The ongoing request can not be abort, which means connection will hang even if we invoke informer.stop() method manually.
• The api of informer is not developer-friendly. Current informer api doesn't have some kind of event like sync which will tell us the data in the cache has been sync after error in the connection. In some situation like synchronizing data from cluster to external database, the sync event is very important because we need to know which data should be deleted from database when it is not in the cluster any more.
• Does not have SharedInformerFactory like client-go. SharedInformer will share the same underlying cache which will reduce a lot of memory use when you use the informer heavily in your application.

What is included:

• An different informer with some apis not included in its counterpart implementation of @kubernetes/client-node (DONE)
• A webRequest implementation based on axios for Watch (DONE)
• A SharedInformerFactory for sharing the same informer of the exact same resource of the same cluser (TO DO)

What is not included

For any other things except the above you want to use to interact with kubernetes cluster, you should use the @kubernetes- node/javascript package.

Installation

// since kubernetes-axios-informer is based on @kubernetes/client-node you need to install it first.
npm install @kubernetes/client-node
npm install kubernetes-axios-informer

Example code

List and watch change of pods resource in the cluster

const k8s = require('@kubernetes/client-node')
const { Watch } = require('@kubernetes/client-node')
const { makeInformer, EVENT, webRequest } = require('kubernetes-axios-informer')

const kc = new k8s.KubeConfig()

kc.loadFromDefault()

const k8sApi = kc.makeApiClient(k8s.CoreV1Api)

const listFn = () => k8sApi.listPodForAllNamespaces()

const podId = (pod) => {
  return `name: ${pod.metadata.name} at namespace ${pod.metadata.namespace}`
}

const informer = makeInformer(kc, '/api/v1/pods', listFn)

informer.on(EVENT.ADD, obj => {
  console.log(`add pod ${podId(obj)}`)
})

informer.on(EVENT.UPDATE, obj => {
  console.log(`updated pod ${podId(obj)}`)
})

informer.on(EVENT.DELETE, obj => {
  console.log(`delete pod ${podId(obj)}`)
})

informer.onSync((pods) => {
  console.log('pod has been resynced, update here')
})

informer.start()
  .then(() => {
    console.log('informer is started')
  })

APIs

Informer

informer.start()

This method will start a informer which means it will start to list and watch in the cluster. Please note that if current informer has been started, this will be a no-ops.

informer.stop()

This method will stop current informer which means no more events will be received.

informer.onSync((objects: T[]) => void)

This method will register an event listener for the resync event. Every time after the informer resync resources from the cluster, the registered event listeners will be called.

informer.on(EVENT: string, callback)

This method is used to register event listeners for informer, the event can be ADD, UPDATE, DELETE or ERROR.

informer.cache

This will return the underlying cache object of this informer.

Cache

cache.list(namespace?: string)

This method will return all of the objects under a namespace. If namespace is not specified, it will return all of the objects in the cache.

cache.get(name: string, namespace?: string)

This method will return the first object with the specified namespace and name.