dapr
/
samples
mirror of https://github.com/dapr/samples.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
samples/read-kubernetes-events/README.md

8.3 KiB
Raw Blame History

Read Kubernetes Events

This tutorial will show an example of running Dapr with a Kubernetes Events Input bindg. You'll be deploying the Node application along with components described.

Prerequisites

This quickstart requires you to have the following installed on your machine:

Also, unless you have already done so, clone the repository with the quickstarts and cd into the right directory:

git clone [-b <dapr_version_tag>] https://github.com/dapr/samples.git
cd samples/read-kubernetes-events

Note: Use git clone https://github.com/dapr/samples.git when using the edge version of dapr runtime.

Step 1 - Make sure that your kubectl client is working

The first thing you need is an RBAC enabled Kubernetes cluster. This could be running on your machine using Minikube, or it could be a fully-fledged cluser in Azure using AKS.

Once you have that make sure you get a positive response from the following kubectl command

kubectl get pods

This should either have output as No resources found in default namespace. or should list the pods running the default namesapce.

Step 2 - Running the code locally

  1. Setup Dapr

Follow instructions to download and install the Dapr CLI and initialize Dapr.

  1. Understand the code

Now that Dapr is set up locally, navigate to the Read Kubernetes Events sample:

cd node

In the app.js you'll find a simple express application, which exposes a single route and handler. First, take a look at the top of the file:

const express = require('express');
const bodyParser = require('body-parser');
require('isomorphic-fetch');
const app = express();
app.use(bodyParser.json());
const port = 3000;

The port defined here is the default port the node app runs on.

Next, take a look at the kube-events handler:

app.post('/kube-events', (req, res) => {
    console.log("Hello from Kube Events!");
    console.log(req.body);
    res.status(200).send();
});

This simple gets the request, prints a log line and the request body in the console.

  1. Understand the component definition:
cd ../components/

Here the yaml file defines the component that Dapr has to register with the particular configuration.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kube-events
  namespace: kube-events
spec:
  type: bindings.kubernetes
  metadata:
  - name: namespace
    value: kube-events
  - name: resyncPreiodInSec
    value: "5"

This registers a bindings.kubernetes component with the name kube-events (which is also the route for the post request) and defines the namespace to watch kube-events and the period to resync with the server 5s.

  1. Run the code locally

The sample uses default kubectl config from the local machine and does not need Dapr or the application to be deployed in Kubernetes. This is simply to illustrate that functionality of the Kubernetes events input binding.

  • Navigate to Node subscriber directory in your CLI: 
      cd ../node
  • Install dependencies: 
      npm install
  • Run Node sample app with Dapr: 
      dapr run --app-id bindings-kevents-nodeapp --app-port 3000 node app.js --components-path ./components

You should see the output:

ℹ️  Updating metadata for app command: node app.js
✅  You're up and running! Both Dapr and your app logs will appear here.
  1. Create a few Kubernetes Events to view through the application

The application is watching the namespace kube-events. If it is already present in your kubernetes cluster you might be seeing some events already. If not follow the steps below.

  • Create namespace kube-events if not present:
kubectl create ns kube-events
  • Deploy a quick Kubernetes hello-world application in the created namespace:
kubectl create deployment hello-node -n kube-events --image=k8s.gcr.io/echoserver:1.4

Output logs from the node application should be of the form:

== APP == Hello from Kube Events!

== APP == {

== APP ==   event: 'add',

== APP ==   oldVal: {

== APP ==     metadata: { creationTimestamp: null },

== APP ==     involvedObject: {},

== APP ==     source: {},

== APP ==     firstTimestamp: null,

== APP ==     lastTimestamp: null,

== APP ==     eventTime: null,

== APP ==     reportingComponent: '',

== APP ==     reportingInstance: ''

== APP ==   },

== APP ==   newVal: {

== APP ==     metadata: {

== APP ==       name: 'hello-node.162c269e7cedc889',

== APP ==       namespace: 'kube-events',

== APP ==       selfLink: '/api/v1/namespaces/kube-events/events/hello-node.162c269e7cedc889',

== APP ==       uid: 'd1baf297-e1e0-462e-8377-ca82ff8eefed',

== APP ==       resourceVersion: '692745',

== APP ==       creationTimestamp: '2020-08-17T20:00:29Z',

== APP ==       managedFields: [Array]

== APP ==     },

== APP ==     involvedObject: {

== APP ==       kind: 'Deployment',

== APP ==       namespace: 'kube-events',

== APP ==       name: 'hello-node',

== APP ==       uid: 'bbb68f59-74e3-40b5-aa2a-dd0769024f99',

== APP ==       apiVersion: 'apps/v1',

== APP ==       resourceVersion: '692741'

== APP ==     },

== APP ==     reason: 'ScalingReplicaSet',

== APP ==     message: 'Scaled up replica set hello-node-7bf657c596 to 1',

== APP ==     source: { component: 'deployment-controller' },

== APP ==     firstTimestamp: '2020-08-17T20:00:29Z',

== APP ==     lastTimestamp: '2020-08-17T20:00:29Z',

== APP ==     count: 1,

== APP ==     type: 'Normal',

== APP ==     eventTime: null,

== APP ==     reportingComponent: '',

== APP ==     reportingInstance: ''

== APP ==   }

== APP == }

Note that the event is categorized as an add event. There are three types of events that the binding monitors add, delete and update events.

  • Delete the deployment just created:
kubectl delete deployment hello-node -n kube-events

Output should be

== APP == Hello from Kube Events!
== APP == {
== APP ==   event: 'delete',
== APP ==   oldVal: {
== APP ==     metadata: {
== APP ==       name: 'hello-node.162c2661c524d095',
== APP ==       namespace: 'kube-events',
== APP ==       selfLink: '/api/v1/namespaces/kube-events/events/hello-node.162c2661c524d095',
== APP ==       uid: '2323b838-6513-487a-bbfb-4ad3138687d9',
== APP ==       resourceVersion: '692240',
== APP ==       creationTimestamp: '2020-08-17T19:56:09Z',
== APP ==       managedFields: [Array]
== APP ==     },
== APP ==     involvedObject: {
== APP ==       kind: 'Deployment',
== APP ==       namespace: 'kube-events',
== APP ==       name: 'hello-node',
== APP ==       uid: '499390b7-da42-4be5-9cf5-284635140b63',
== APP ==       apiVersion: 'apps/v1',
== APP ==       resourceVersion: '692131'
== APP ==     },
== APP ==     reason: 'ScalingReplicaSet',
== APP ==     message: 'Scaled up replica set hello-node-7bf657c596 to 1',
== APP ==     source: { component: 'deployment-controller' },
== APP ==     firstTimestamp: '2020-08-17T19:56:09Z',
== APP ==     lastTimestamp: '2020-08-17T19:56:09Z',
== APP ==     count: 1,
== APP ==     type: 'Normal',
== APP ==     eventTime: null,
== APP ==     reportingComponent: '',
== APP ==     reportingInstance: ''
== APP ==   },
== APP ==   newVal: {
== APP ==     metadata: { creationTimestamp: null },
== APP ==     involvedObject: {},
== APP ==     source: {},
== APP ==     firstTimestamp: null,
== APP ==     lastTimestamp: null,
== APP ==     eventTime: null,
== APP ==     reportingComponent: '',
== APP ==     reportingInstance: ''
== APP ==   }
== APP == }

Note that the event is categorized as a delete event.

  • Delete namepace (if it was created for this sample):
kubectl delete ns kube-events

Step 3 - Running in kubernetes cluster

Next steps

  • Explore additional samples and deploy them locally or on Kubernetes.