HelloWorld!

An Introductory Knative Demo

Note: this version uses Knative v0.6.0. Look at the releases to find instructions for how to run the demo on older versions.

This repo contains the source code, tools and instructions for a demo that shows using Knative on the IBM Cloud Kubernetes Service. You can pretty easily convert it to work on other platforms.

The main reasons behind this are:

showcase the basics of Knative so you can jump-start your usage of it
showcase some of the newer features of Knative, meaning this demo will grow over time as new features are added to Knative
to share my experiences during this exercise
highlight some areas where I think Knative can be improved

If you want use the demo script, it will show the commands in bold and the output of the commands in normal text. When it pauses, just press the spacebar to move to the next step. If the slow typing is annoying, press f when it pauses and it'll stop that.

Also, these scripts are tested on Ubuntu, I haven't tried them on MacOS yet so don't be surprised if things don't work there yet. PR are welcome though.

So, with that, let's get started...

Canned demo!

If you just want to see what a successful demo looks like without actually doing anything, like even installing Kubernetes or Knative, just run this:

$ USESAVED=1 ./demo

And press the spacebar to walk through each command. The output should look basically the same as a live-run (even with delays at the right times) to make it look-n-feel like it's live! Great for situations where your network isn't reliable, or the demo Gods are mad at you.

Prep

To run the demo yourself, there are a couple of things you'll need to do. First, fork and clone this repo. Cloning alone isn't good enough because as part of the demo we will be updating some files and pushing them back to Github to demonstrate how to build new container images as your source code changes.

Once you've cloned the repo, you'll need to create a .secrets file in the root of the clone directory that looks like this:

git_accesstoken=...
git_secrettoken=...
username=...
password=...

Where:

git_accesstoken is a Github Personal Access Token
git_secrettoken is the secret token you want the events from Github to use to verify they're authenticated with your Knative subscription. This can basically be any random string you want.
username is your container registry (e.g. Dockerhub) username
password is your container registry (e.g. Dockerhub) password

I store all of the secret information I use during the demo in there. It's safer to put them in there than to put them into the real files of the repo and run the risk of checking them into github by mistake.

The rest of this assumes you:

are already logged into the IBM Cloud (ibmcloud login)
and have all of the appropriate CLI tools installed - see: https://github.com/IBM/knative101/workshop/exercise-0/README.md

Creating a Kubernetes cluster

Note: in order to run this demo you'll need a cluster with at least 3 worker nodes in it. As of now this means that you can not use a free-tier cluster.

To help with the process of creating a Kubernetes cluster, I've automated this via the mkcluster script in the repo. The script assumes you're using the Dallas data center, so if not you'll need to modify it.

To create the cluster just run:

$ ./mkcluster CLUSTER_NAME

And you can then skip to the next section.

If you decide to create it manually, then you'll first need to get some info about our LANs since the ibmcloud ks cluster-create command requires that:

$ ibmcloud ks vlans --zone dal13
OK
ID        Name   Number   Type      Router         Supports Virtual Workers
PRIV_??          1240     private   bcr02a.dal13   true
PUB_??           996      public    fcr02a.dal13   true

Now we can create the cluster. In this case we'll create it with 3 worker nodes. Replace the PRIV_?? and PUB_?? with the values you see from the ibmcloud ks vlans command - and replace dal13 with whatever data center you want to use.

$ ibmcloud ks cluster-create --name CLUSTER_NAME --zone dal13 \
    --machine-type ${MACHINE} --workers 3 \
	--private-vlan PRIV_?? --public-vlan PUB_??  \
    --kube-version 1.13.2
Creating cluster...
OK

Once the cluster is ready you'll need to set your KUBECONFIG environment variable to point to your customized Kubernetes config file:

$(ibmcloud ks cluster-config --export CLUSTER_NAME)

Now we can install Knative...

Knative requires Istio, but luckily IBM Cloud's Kubernetes service's install of Knative will install Istio too - just run:

$ ibmcloud ks cluster-addon-enable knative CLUSTER_NAME

If it prompts you to install Istio, just say yes, even if you have Istio already installed - worst case, it'll upgrade it for you.

Since Knative is still very much a work-in-progress, and while the IKS team will try to keep up with the latest versions, if you happen to catch things at a time when the IKS install of Knative is behind the latest version, and you want the very latest version just follow these instructions for how to install the latest Knative manually.

This will take a moment or two, and you can see it's done when two things happen, first you see the Istio and Knative namespaces:

$ kubectl get ns -w
NAME                 STATUS   AGE
default              Active   39h
ibm-cert-store       Active   39h
ibm-system           Active   39h
istio-system         Active   21h    <----
knative-build        Active   18h    <----
knative-eventing     Active   18h    <----
knative-monitoring   Active   18h    <----
knative-serving      Active   18h    <----
knative-sources      Active   18h    <----
kube-public          Active   39h
kube-system          Active   39h

When you see the istio-system and the knatve-... ones appear then you're almost done. Press control-C to stop the watch.

Next, check to see if all of the pods are running. I find it easiest to just see if there are any pods that are not running, via this:

$ kubectl get pods --all-namespaces | grep -v Running

And if that list is empty, or only shows non-Istio and non-Knative pods (due to other things running in your cluster) then you should be good to go. If the list isn't empty, then give it more time for things to initialize.

Running the demo

You can now either run the demo script to have it automatically run through the demo, providing commentary, or you can do it all manually.

Which ever way you run the demo, I'd run ./pods in another window so you can see the Knative Services and Pods as they come-n-go. Make sure you run $(ibmcloud ks cluster-config --export CLUSTER_NAME) in that other window too.

Before you begin, set these environment variables:

$ export APP_IMAGE=duglin/helloworld
$ export REBUILD_IMAGE=duglin/rebuild
$ export GITREPO=duglin/helloworld

Set APP_IMAGE and REBUILD_IMAGE values to use your Dockerhub namespace name instead of duglin, and change GITREPO to be the name of your Github clone of this repo - typically you should just need to swap duglin for your Github name.

Using the `demo` script

To have the computer type all of the demo commands for you, just run:

$ ./demo [ CLUSTER_NAME ]

CLUSTER_NAME is optional if your KUBECONFIG environment variable already points to your IKS cluster.

When the demo is done you can jump the the Cleaning Up section.

Manually running the demo / Demo details

This section will walk through the steps executed by the demo script providing commentary as you do each step.

Secrets

Before we get to the real point of this, which is deploying an application, we needed to create a Kuberneres Secret that holds all of the private keys/tokens/usernames/etc... that will be used during the demo. We also needed to create some new RBAC rules so that our "rebuild" service, which is running under the "default" Service Account, has the proper permissions to access and edit the Knative Service to force it to rebuild - which I'll talk more about later.

For all of these things I have the secrets.yaml file:

apiVersion: v1
kind: Secret
metadata:
  name: mysecrets
  annotations:
    build.knative.dev/docker-0: https://index.docker.io/v1/
type: kubernetes.io/basic-auth
stringData:
  git_accesstoken: ${.secrets.git_accesstoken}
  git_secrettoken: ${.secrets.git_secrettoken}
  username: ${.secrets.username}
  password: ${.secrets.password}
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: build-bot
secrets:
- name: mysecrets

---
# Give our "default" ServiceAccount permission to touch Knative Services
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: rebuild
rules:
- apiGroups:
  - serving.knative.dev
  resources:
  - services
  verbs:
  - get
  - list
  - update
  - patch
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: rebuild-binding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: rebuild
subjects:
- kind: ServiceAccount
  name: default
  namespace: default

You'll notice some environment variable looking values in there. Obviously, those are not normal Kube yaml things. To make life easier, I created a script called kapply which takes a yaml file and replaces references like those with their real values before invoking kubectl apply. This allows me to share my yaml with you w/o asking you to modify these files and run the risk of you checking them into your github repo by mistake. All you need to do is create the .secrets files I mentioned previously.

Then you can create the secret via:

$ ./kapply secrets.yaml
secret/mysecrets created
serviceaccount/build-bot created
clusterrole.rbac.authorization.k8s.io/rebuild created
clusterrolebinding.rbac.authorization.k8s.io/rebuild-binding created

Our application

For this demo I'm just using a very simple HTTP server that responds to any request with Hello World! plus whatever text is in the MSG environment variable.

Here's the source (helloworld.go):

package main

import (
    "fmt"
    "net/http"
    "os"
    "strings"
    "time"
)

func main() {
    text := "Hello World!"

    if os.Getenv("MSG") != "" {
        text += " " + os.Getenv("MSG")
    }

    rev := os.Getenv("K_REVISION") // K_REVISION=helloworld-7vh75
    if i := strings.LastIndex(rev, "-"); i > 0 {
        rev = rev[i+1:] + ": "
    }

    msg := fmt.Sprintf("%s%s\n", rev, text)

    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Printf("Got request\n")
        time.Sleep(500 * time.Millisecond)
        fmt.Fprint(w, msg)
    })

    fmt.Printf("Listening on port 8080 (rev: %s)\n", rev)
    http.ListenAndServe(":8080", nil)
}

The sleep is in there just to slow things down a bit so that when we increase the load on the app it'll cause one instance of the app to be created for each client we have generating requests. It makes for a better live demo experience.

The app will print part of the K_REVISION environment variable so we can see which revision number of our app we're hitting.

If you look in the Makefile you'll see how I built and pushed it to my namespace in Dockerhub:

docker build -t $(APP_IMAGE) .
docker push $(APP_IMAGE)

You'll need to modify the Makefile to point to your DockerHub namespace if you want to use make.

Now, our first adventure with Knative... let's deploy the application as a Knative Service. First, do not confuse a Knative Service with a Kubernetes Service - they're not the same thing. This is an on-going point of discussion within the Knative community, so for now we just need to live with it.

We'll first deploy our Knative Service the really easy way, via the Knative kn command line tool. The source code is available at https://github.com/knative/client . For convinience, I've included the kn exectuable in this directory - but it's only for Linux.

$ ./kn service create helloworld --image ${APP_IMAGE}
Service 'helloworld' successfully created in namespace 'default'.
Waiting for service 'helloworld' to become ready ... OK

Service URL:
http://helloworld-default.v06.us-south.containers.appdomain.cloud

As should be clear from the first two arguments, this kn command is creating a service. The next argument is the service name (helloworld) and then we give it the name/location of the container image to use.

Once the command is done, you'll see that it shows you the URL where the service is available. IKS will automatically configure the networking infrastructure for you and give you a nice DNS name so you don't need to do any of that yourself.

With that URL you can now hit (curl) it:

$ curl -sf http://helloworld-default.v06.us-south.containers.appdomain.cloud
krc9z: Hello World!

With that, you've now successfully deploy a Knative Service and behind the scenes it created all of the Kubernetes resources to host it, scale it, route traffic to it and even give it a relatively nice URL.

One more thing.... you can also access it via SSL:

$ curl -sf https://helloworld-default.v06.us-south.containers.appdomain.cloud
krc9z: Hello World!

So, you also get security too! All with one simple command.

Let's take a quick look at all of the resources that were created for us:

$ ./showresources all
deployment.apps/helloworld-krc9z-deployment
endpoint/helloworld-krc9z
endpoint/helloworld-krc9z-metrics
endpoint/helloworld-krc9z-priv
endpoint/kubernetes
pod/helloworld-krc9z-deployment-7875dcb55-cdksl
replicaset.apps/helloworld-krc9z-deployment-7875dcb55
service/helloworld
service/helloworld-krc9z
service/helloworld-krc9z-metrics
service/helloworld-krc9z-priv
service/kubernetes

clusterchannelprovisioner.eventing.knative.dev/in-memory
clusteringress.networking.internal.knative.dev/route-032c8cb8-6faa-4bdb-8fcf-4db63337b91b
configuration.serving.knative.dev/helloworld
image.caching.internal.knative.dev/helloworld-krc9z-cache
podautoscaler.autoscaling.internal.knative.dev/helloworld-krc9z
revision.serving.knative.dev/helloworld-krc9z
route.serving.knative.dev/helloworld
serverlessservice.networking.internal.knative.dev/helloworld-krc9z
service.serving.knative.dev/helloworld

The first list is the list of core Kube resources, and the second list contains the Knative ones. That's a lot of stuff! And I mean that in a good way! One of my hopes for Knative is to offer up a more user friendly user experience for Kube users. Sure Kube has a ton of features but with that flexibility has come complexity. Think about how much learning and work is required to setup all of these resources that Knative as done for us. We no longer need to understand Ingress, load-balancing, auto-scaling, etc. Very nice!

Back to our demo...

The kn command line is still under development so for the rest of this write-up I'm going to switch back to the normal Kubernetes CLI, kubectl. And to do that, let's delete this service so we can see how to do it with kubectl.

$ ./kn service delete helloworld
Service 'helloworld' successfully deleted in namespace 'default'.

Let's first look at our yaml file that defines our Knative Service defined in service1.yaml:

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: helloworld
spec:
 template:
    spec:
      containers:
        - image: duglin/helloworld

Let's explain what some of these fields do:

metadata.name: Like all Kube resources, this names our Service, and matches what we put on the kn command line.
spec.template: One concept that might take some getting used to is the notion that the spec.template section of a Knative Service resource doesn't really define the Service itself directly. The better way to think of it is that you provide it a "template" for what the next version (revision) of your service should look like. While in practice, yes the spec.template will normally match what the service currently looks like, it may be important at times to understand that behind the scenes each version of your service has an associated Revison resource with its own unique configuration information - which is populated from this template. But for now, it's ok to think of spec.template as your desired state for the latest version of the Service.`
spec.template.spec: This is taken directly from the Kubernetes Pod spec defintion. Meaning, you can put anything from the Pod spec in here to define your app. However, while from a syntax perspective you should be able to copy-n-paste your Pod spec into here, since Knative doesn't support all of the Pod's features you may get an error message in some cases if you use a feature that Knative doesn't support yet.
spec.template.spec.containers.image: This just defines which container image this version of the Service should use. Same as what we saw on the kn command line.

For the most part you'll see that there really are only 2 pieces of information in here - the service name and the image name. Same as the kn command line. There's just more yaml because, well, it's yaml and Kubernetes.

Now we can deploy it:

$ ./kapply service1.yaml
service.serving.knative.dev/helloworld created

If you're not running pods in another window, run it now to see what happened:

$ ./pods
Cluster: v06
NS/NAME                        LATESTREADY                    READY
helloworld                     helloworld-9frrr               True    

POD_NAME                                                STATUS           AGE
helloworld-9frrr-deployment-65b66d976d-j8q7w            Running          5s

The output of pods shows the list of Knative services (at the top) followed by the list of active pods.

When the pod is in the Running state, press control-C to stop it.

You should see your helloworld Knative service with one revision called something like helloworld-9frrr, and a pod with a really funky name but that starts with that revision name.

Notice the word "deployment" in there - that's because under the covers Knative created a Kubernetes Deployment resource and this pod is related to that Deployment.

So, it's running - let's invoke it, and we can use the same URL as before when we used the kn command. But if you forgot it, you can do this:

$ kubectl get ksvc
NAME         DOMAIN                                                             LATESTCREATED      LATESTREADY        READY   REASON
helloworld   http://helloworld-default.v06.us-south.containers.appdomain.cloud  helloworld-9frrr   helloworld-9frrr   True

You'll notice that once the Service is ready the "DOMAIN" column will show the full URL of the Service.

$ curl -sf http://helloworld-default.v06.us-south.containers.appdomain.cloud
9frrr: Hello World!

That's it. Notice that the deployment of the Service was pretty easy whether you use the kn or the kubectl command line tool. And that's a huge step forward for Kubernetes users.

Updating Our Service

Now that we have our app running, let's make some changes and roll out a new version. Let's look at the next yaml file we'll use:

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: helloworld
spec:
  template:
    metadata:
      name: helloworld-v1
    spec:
      containers:
      - image: duglin/helloworld
      containerConcurrency: 1
  traffic:
  - tag: helloworld-v1
    revisionName: helloworld-v1
    percent: 100

You should notice 2 main differences here:

spec.template.metadata.name: This is different from the Service name you'll see above on the 4th line. This provides a name for this revision of your service. We're going to provide a name so that we can reference it in the traffic section below.
spec.traffic: This section allows for us to tell Knative how to route traffic between the various versions (revisions) of our Service. This is useful when you want to do a rolling (A/B) update of your service rather than switch all traffic to the new version immediately.

In this case we're defining just one traffic section and telling Knative to send all (100%) of the traffic to the revision called helloworld-v1 - which is what we're naming the new revision. You'll notice there's tag property too - this allows us to give a unique prefix to a specialize URL for just that one revision if you want to send request directly to it and avoid the percentage based routing logic. In this case, to keep it simple, we picked the same name as the revision.

Once final thing, there's also now containerConcurrency property in there. We're setting that to 1 so that each instance of the service will only process one request at time, instead of multiple. This makes for a better demo when we generate a load since it'll force the Service to scale up pretty quickly.

With that, let's go ahead and apply this yaml to update our service:

$ ./kapply service2.yaml
service.serving.knative.dev/helloworld configured

In the "pods" window you should see something like this:

$ ./pods
Cluster: v06
NS/NAME                        LATESTREADY                    READY
helloworld                     helloworld-v1                  True

POD_NAME                                                STATUS           AGE
helloworld-9frrr-deployment-65b66d976d-j8q7w            Running          23s
helloworld-v1-deployment-6bfbd447c-8x8wp                Running          11s

Notice that we now have a 2nd revision and it's name is helloworld-v1.

Hitting it you should see:

$ curl -sf http://helloworld-default.v06.us-south.containers.appdomain.cloud
v1: Hello World!

Notice we use the same URL but now the version number on the output shows v1.

Traffic Splitting

With that brief introduction to traffic management, let's actually do some real traffic splitting by deploying a 3rd version of the app:

$ ./kapply -t service3.yaml
apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: helloworld
spec:
  template:
    metadata:
      name: helloworld-v2
    spec:
      containers:
      - image: duglin/helloworld
        env:
        - name: MSG
          value: Goodnight Moon!
      containerConcurrency: 1
  traffic:
  - tag: helloworld-v1
    revisionName: helloworld-v1
    percent: 50
  - tag: helloworld-v2
    revisionName: helloworld-v2
    percent: 50

Couple of things to notice here:

We named this version of the app helloworld-v2.
We added an environment variable called MSG to the app. This just allows us to see some different output when we hit this version.
We've modified the traffic section so that we now have two versions of the app that will get traffic. Each gets 50% and the two versions are the v1 and v2 versions. The initial version we deployed will eventually be removed from the system since we never reference it in a traffic section.

Let's deploy this:

$ ./kapply service3.yaml
service.serving.knative.dev/helloworld configured

We can now generate some load on our service and we should see roughly 1/2 of the traffic go to v1 and 1/2 go to v2:

$ ./load 10 10 http://helloworld-default.v06.us-south.containers.appdomain.cloud

01: v1: Hello World!                                                            
02: v1: Hello World!                                                            
03: v1: Hello World!                                                            
04: v2: Hello World! Goodnight Moon!                                            
05: v1: Hello World!                                                            
06: v2: Hello World! Goodnight Moon!                                            
07: v2: Hello World! Goodnight Moon!                                            
08: v2: Hello World! Goodnight Moon!                                            
09: v2: Hello World! Goodnight Moon!                                            
10: v2: Hello World! Goodnight Moon!

The load command (as specified) will simulate 10 clients hitting the URL for 10 seconds. Notice we do in fact see both versions getting hit.

Hidden Traffic

The traffic split we did the previous section was nice, but often times when you deploy a new version of an app you don't want it exposed to your users right away. Perhaps you only want your tests to hit it. Knative can help here too. Let's look at another version of the yaml:

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: helloworld
spec:
  template:
    metadata:
      name: helloworld-v2
    spec:
      containers:
      - image: duglin/helloworld
        env:
        - name: MSG
          value: Goodnight Moon!
      containerConcurrency: 1
  traffic:
  - tag: helloworld-v1
    revisionName: helloworld-v1
    percent: 50
  - tag: helloworld-v2
    revisionName: helloworld-v2
    percent: 50
  - tag: helloworld-test
    latestRevision: true
    percent: 0

Here we didn't modify anything about the template but we did add a new traffic section. In there we told Knative a couple of things. First, we gave it a name via the tag - helloworld-test. As before, this is just some unique prefix for a dedicated URL we can use to talk to the revision pointed to by this traffic section. Next, the latestRevision property. If we have a name of a version we wanted to reference we could have put that name on revisionName property, but in this case we're asking Knative to make this traffic section point to the very latest version of the app regardless of what its name is.

Finally, we told Knative to send no traffic (0 percent) to this version we're pointing to. This means that when people hit our main URL they'll never talk to this revision. The only way we can talk to this one is via the dedicated URL that Knative will setup for us. One thing to note is that as of right now the "latest" version of the app just happens to be "v2" so both the 2nd and 3rd traffic sections actually point to the same version - and that's ok.

We're doing all of this because in the next section we'll be updating our app and I want to show how only traffic to the helloworld-test URL will be able to see it.

Let's deploy it:

$ ./kapply service4.yaml
service.serving.knative.dev/helloworld configured

Adding Build

In this part of the demo we're going to connect our Github account up to our service so that when a new "push" to the "master" branch happens we'll kick off a build of our app and deploy it.

To do this we'll first need to deply a "rebuild" service. This is really nothing more than a Knative Service that waits for an incoming HTTP request from Github's webhook system. When that request indicates that it was a "push" event on our git repo, we'll kick off a build of the latest version of the source, build a new container image and the deploy a new version of our app using that image.

I'm not going to get into how the "rebuild" service works, but if you really want to see it you can look at the source code: rebuild.go.

To deploy it we'll apply this yaml:

apiVersion: serving.knative.dev/v1alpha1
kind: Service
metadata:
  name: rebuild
spec:
  template:
    spec:
      containers:
        - image: ${REBUILD_IMAGE}
          env:
          - name: KSVC
            value: helloworld
          - name: GITREPO
            value: ${GITREPO}
          - name: APP_IMAGE
            value: ${APP_IMAGE}

You'll notice that we pass in some environment variables telling it which git repo to get the source from, which Knative service to update, and where to store the built image.

Let's execute that:

$ ./kapply rebuild.yaml
service.serving.knative.dev/rebuild created

Now we need to connect this "rebuild" service up to Github. To do this we'll use Knative Eventing. As part of Eventing there are things called "importers". You can think of these as utilities that help you subscribe and manage events from event producers. In this case we're going to deploy a Github importer (also known as an "event source") that will talk to Github for us to create the webhook for our git repo and tell it to send events to the importer, who will then pass it on to our rebuild service.

One thing I need to mention, the event that is passed on to the Knative service is a CloudEvent. All that means is that some common metadata about the event (such as who sent it or what its type is) are in well-defined locations so that regardless of who the event producer is, your code should be able to get that information by just looking at one specific location. Just to make life a little easier.

To set this up we'll use this yaml:

apiVersion: sources.eventing.knative.dev/v1alpha1
kind: GitHubSource
metadata:
  name: githubsource
spec:
  eventTypes:
    - push
  ownerAndRepository: duglin/helloworld
  accessToken:
    secretKeyRef:
      name: mysecrets
      key: git_accesstoken
  secretToken:
    secretKeyRef:
      name: mysecrets
      key: git_secrettoken
  sink:
    apiVersion: serving.knative.dev/v1alpha1
    kind: Service
    name: rebuild

Walking through this:

you'll see the types of events (push) that we're asking for.
the ownerAndRepository property tells it which git repo to subscribe to.
the accessToken contains the credentials needed for it to talk to Github for me - and it gets those credentials from the Kubernetes secret referenced in there.
secretToken is just the auth token we expect Github to use on the events sent to us so we can verify they're actually related to this subscription/webhook.
And finally, we provide a sink which is where the event should be sent to. Which in this case is our 'rebuild' service.

Technically, we could have done of this ourselves, but this just makes it easier. And when we delete this resource it'll delete the webhook for us too.

Let's deploy it:

$ ./kapply github.yaml
githubsource.sources.eventing.knative.dev/githubsource created

If you go to your gitrepo repo's webhook page you should see an entry listed in there for it - and it should look something like this:

Don't be surprised if the green check is actually a red "X", sometimes the first (a verification message) has issues.

Editing Our App

With that infrastructure ready, let's edit our app and see it all in action.

In your favorite editor, edit the "Hello World" message to something else. Or just run this command:

$ sed -i "s/text :=.*/text := \"Dogs rule!! Cats drool!!\"/" helloworld.go

Then let's commit it and push it to github:

$ git add helloworld.go

$ git commit -s -m "demo - Fri Aug 2 07:39:39 PDT 2019"
[master 2173aed] demo - Fri Aug  2 07:39:39 PDT 2019
 2 files changed, 4 insertions(+), 2 deletions(-)

$ git push origin master
To [email protected]:duglin/helloworld.git
   6b580c0..2173aed  master -> master

The entire build process takes about 30 seconds, but in your "pods" window you should see the "rebuild" and "githubsource" pods appear, as well as some "build" pod. Eventually a new revision pod for the service should appear too.

If you curl the "helloworld-test" revision (via the special URL setup under the Traffic section), you should see something like this:


$ curl -sf http://helloworld-helloworld-test-default.v06.us-south.containers.appdomain.cloud
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
hwwx2: Dogs rule!! Cats drool!! Goodnight Moon!

Notice that it will show v2 of the app until the re-deploy is done and then all traffic will switch over the latest version. Keep in mind, this is only what the special "helloworld-test" URL will see because that's the only one pointing to the latest version of the app.

Likewise, we could also hit just v1 or v2 directly:

$ curl -sf http://helloworld-helloworld-v1-default.v06.us-south.containers.appdomain.cloud
v1: Hello World!

$ curl -sf http://helloworld-helloworld-v2-default.v06.us-south.containers.appdomain.cloud
v2: Hello World! Goodnight Moon!

The main URL for the app is still routing traffic between v1 and v2.

To prove that run this:

$ for i in `seq 1 20` ; do curl -s http://helloworld-default.v06.us-south.containers.appdomain.cloud ; done
v1: Hello World!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v1: Hello World!
v1: Hello World!
v1: Hello World!
v2: Hello World! Goodnight Moon!
v1: Hello World!
v1: Hello World!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v1: Hello World!
v2: Hello World! Goodnight Moon!
v2: Hello World! Goodnight Moon!
v1: Hello World!
v2: Hello World! Goodnight Moon!
v1: Hello World!
v1: Hello World!

Notice that we never see the latet version that talks about dogs and cats.

Scary!

Now, just to show you how much Knative has saved us with respect to managing Kubernetes resources, let's run showresources again:

$ ./showresources all
deployment.apps/githubsource-7bk5d-24srp-deployment
deployment.apps/helloworld-9frrr-deployment
deployment.apps/helloworld-hwwx2-deployment
deployment.apps/helloworld-v1-deployment
deployment.apps/helloworld-v2-deployment
deployment.apps/rebuild-xkdrt-deployment
endpoint/githubsource-7bk5d-24srp
endpoint/githubsource-7bk5d-24srp-metrics
endpoint/githubsource-7bk5d-24srp-priv
endpoint/helloworld-9frrr
endpoint/helloworld-9frrr-metrics
endpoint/helloworld-9frrr-priv
endpoint/helloworld-hwwx2
endpoint/helloworld-hwwx2-metrics
endpoint/helloworld-hwwx2-priv
endpoint/helloworld-v1
endpoint/helloworld-v1-metrics
endpoint/helloworld-v1-priv
endpoint/helloworld-v2
endpoint/helloworld-v2-metrics
endpoint/helloworld-v2-priv
endpoint/kubernetes
endpoint/rebuild-xkdrt
endpoint/rebuild-xkdrt-metrics
endpoint/rebuild-xkdrt-priv
pod/build-helloww94q-pod-50369b
pod/githubsource-7bk5d-24srp-deployment-ffb59c865-6wq5g
pod/helloworld-hwwx2-deployment-7d7df9558c-wl55z
pod/helloworld-v1-deployment-6bfbd447c-5wm8m
pod/helloworld-v2-deployment-77bbc9d98c-9jn8g
pod/rebuild-xkdrt-deployment-7b5c4648c6-v2pxk
replicaset.apps/githubsource-7bk5d-24srp-deployment-ffb59c865
replicaset.apps/helloworld-9frrr-deployment-65b66d976d
replicaset.apps/helloworld-hwwx2-deployment-7d7df9558c
replicaset.apps/helloworld-v1-deployment-6bfbd447c
replicaset.apps/helloworld-v2-deployment-77bbc9d98c
replicaset.apps/rebuild-xkdrt-deployment-7b5c4648c6
service/githubsource-7bk5d
service/githubsource-7bk5d-24srp
service/githubsource-7bk5d-24srp-metrics
service/githubsource-7bk5d-24srp-priv
service/helloworld
service/helloworld-9frrr
service/helloworld-9frrr-metrics
service/helloworld-9frrr-priv
service/helloworld-helloworld-test
service/helloworld-helloworld-v1
service/helloworld-helloworld-v2
service/helloworld-hwwx2
service/helloworld-hwwx2-metrics
service/helloworld-hwwx2-priv
service/helloworld-v1
service/helloworld-v1-metrics
service/helloworld-v1-priv
service/helloworld-v2
service/helloworld-v2-metrics
service/helloworld-v2-priv
service/kubernetes
service/rebuild
service/rebuild-xkdrt
service/rebuild-xkdrt-metrics
service/rebuild-xkdrt-priv
taskrun.tekton.dev/build-helloww94q

clusterchannelprovisioner.eventing.knative.dev/in-memory
clusteringress.networking.internal.knative.dev/route-42b0f459-578b-4fbe-845c-90017af34a74
clusteringress.networking.internal.knative.dev/route-7422c2f8-9359-4f58-a858-af21a24d8fa3
clusteringress.networking.internal.knative.dev/route-752e3da4-e6f2-42fb-aae3-cb885ab55a36
configuration.serving.knative.dev/githubsource-7bk5d
configuration.serving.knative.dev/helloworld
configuration.serving.knative.dev/rebuild
githubsource.sources.eventing.knative.dev/githubsource
image.caching.internal.knative.dev/githubsource-7bk5d-24srp-cache
image.caching.internal.knative.dev/helloworld-9frrr-cache
image.caching.internal.knative.dev/helloworld-hwwx2-cache
image.caching.internal.knative.dev/helloworld-v1-cache
image.caching.internal.knative.dev/helloworld-v2-cache
image.caching.internal.knative.dev/rebuild-xkdrt-cache
podautoscaler.autoscaling.internal.knative.dev/githubsource-7bk5d-24srp
podautoscaler.autoscaling.internal.knative.dev/helloworld-9frrr
podautoscaler.autoscaling.internal.knative.dev/helloworld-hwwx2
podautoscaler.autoscaling.internal.knative.dev/helloworld-v1
podautoscaler.autoscaling.internal.knative.dev/helloworld-v2
podautoscaler.autoscaling.internal.knative.dev/rebuild-xkdrt
revision.serving.knative.dev/githubsource-7bk5d-24srp
revision.serving.knative.dev/helloworld-9frrr
revision.serving.knative.dev/helloworld-hwwx2
revision.serving.knative.dev/helloworld-v1
revision.serving.knative.dev/helloworld-v2
revision.serving.knative.dev/rebuild-xkdrt
route.serving.knative.dev/githubsource-7bk5d
route.serving.knative.dev/helloworld
route.serving.knative.dev/rebuild
serverlessservice.networking.internal.knative.dev/githubsource-7bk5d-24srp
serverlessservice.networking.internal.knative.dev/helloworld-9frrr
serverlessservice.networking.internal.knative.dev/helloworld-hwwx2
serverlessservice.networking.internal.knative.dev/helloworld-v1
serverlessservice.networking.internal.knative.dev/helloworld-v2
serverlessservice.networking.internal.knative.dev/rebuild-xkdrt
service.serving.knative.dev/githubsource-7bk5d
service.serving.knative.dev/helloworld
service.serving.knative.dev/rebuild

That's a ton of stuff we'd have to manage ourselves!

Tekton

I didn't talk about how the build of the app itself is done, and I won't go into too many details other than to say it uses Tekton under the covers.

You can think of Tekton in the same light as a Jenkins system. It will run a set of steps that you tell it. And if you look at task.yaml you'll see the yaml file that defines those steps. In this case, it's just two steps

run a container called kaniko-project/executor that will do a Docker build and push the resulting image to a container registry
issue a curl command (via the duglin/curl container) to poke the rebuild service so it knows when the new image is ready so it can deploy the next version of the service

Ideally, I would have preferred to make it so that the "rebuild" service got a real event from DockerHub directly when the push happened so that I didn't have to do the curl command, but there is no DockerHub importer yet - but maybe one day.

There are also some niceties in there, like by specifying an input as a github repo it'll do the clone for me automatically. Which is kind of nice.

The intersting thing about this to me is that I still can't quite decide how Tekton will be used. By that I mean, will people create tasks with lots of individual steps (similar to the steps they might see in a Makefile), or will the steps be fairly large which would results in a relatively small number of them in each job.

I also wonder if most jobs will end up being close to just one step, and people will encode a ton of logic into there - more like just wrappering your make command in a container. And if so, it'll be interesting to see where people see the benefit of Tekton vs just running the container directly.

Summary

With that we're run through a pretty extensive demo. To recap, we:

deployed a pre-built container image as a Knative service, but via kn and kubectl
showed how to create multiple version of the service and route traffic to each based on a percentage.
showed how to create an event "importer" to subscribe to an event producer and have those events sent on to a Knative service
showed how to bring it all together to have a mini CI/CD pipeline that will build and redeploy our service as we make changes to its github repo

Overall, what's out there today is a HUGE useability improvement for developers. The idea of being able to create and manipulate the Kubernetes resource to do all of these (what I consider) advanced semantics is really very exciting, and I can't wait to see how things progress.

Cleaning up

To clean the system so you can run things over and over, just do:

$ ./demo --clean

It should delete everything except the cluster, Istio and Knative.

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Repository files navigation

HelloWorld!

An Introductory Knative Demo

Canned demo!

Prep

Creating a Kubernetes cluster

Running the demo

Using the `demo` script

Manually running the demo / Demo details

Secrets

Our application

Updating Our Service

Traffic Splitting

Hidden Traffic

Adding Build

Editing Our App

Scary!

Tekton

Summary

Cleaning up

About

Releases 5

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Name		Name	Last commit message	Last commit date
Latest commit History 477 Commits
.demoscript		.demoscript
.env		.env
.gitignore		.gitignore
Dockerfile		Dockerfile
Dockerfile.bash		Dockerfile.bash
Dockerfile.rebuild		Dockerfile.rebuild
Knative - Meetup 2019-04-25.pdf		Knative - Meetup 2019-04-25.pdf
Knative - THINK 2019.pdf		Knative - THINK 2019.pdf
Makefile		Makefile
README.md		README.md
demo		demo
demo.tar		demo.tar
github.yaml		github.yaml
helloworld.go		helloworld.go
ingress.yaml		ingress.yaml
kapply		kapply
load.go		load.go
mkcluster		mkcluster
pods		pods
rebuild.go		rebuild.go
rebuild.yaml		rebuild.yaml
secrets.yaml		secrets.yaml
service-patch.json		service-patch.json
service1.yaml		service1.yaml
service2.yaml		service2.yaml
service3.yaml		service3.yaml
service4.yaml		service4.yaml
showresources		showresources
task.yaml		task.yaml
webhooks.png		webhooks.png

duglin/helloworld

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HelloWorld!

An Introductory Knative Demo

Canned demo!

Prep

Creating a Kubernetes cluster

Running the demo

Using the demo script

Manually running the demo / Demo details

Secrets

Our application

Updating Our Service

Traffic Splitting

Hidden Traffic

Adding Build

Editing Our App

Scary!

Tekton

Summary

Cleaning up

About

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Using the `demo` script

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