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Sneak Peek: Linkerd 2.13

This is the documentation - and executable code! - for the Service Mesh Academy workshop about what's coming in Linkerd 2.13. The easiest way to use this file is to execute it with demosh.

Things in Markdown comments are safe to ignore when reading this later. When executing this with demosh, things after the horizontal rule below (which is just before a commented @SHOW directive) will get displayed.

For this workshop, you'll need a running, empty, Kubernetes cluster that can support LoadBalancer services. You can use create-cluster.sh to create an appropriate k3d cluster.

BAT_STYLE="grid,numbers"

Sneak Peek: Linkerd 2.13

Welcome to the Service Mesh Academy Sneak Peek for Linkerd 2.13!

We're going to start by installing the most recent edge release of Linkerd, since stable-2.13.0 isn't out yet:

curl --proto '=https' --tlsv1.2 -sSfL https://run.linkerd.io/install-edge | sh

Once that's done, we can proceed to install Linkerd into our cluster.

linkerd check --pre
linkerd install --crds | kubectl apply -f -
linkerd install | kubectl apply -f -
linkerd check

We're already running the Faces demo (https://github.com/BuoyantIO/faces-demo) with Emissary-ingress for an ingress controller. Let's get them into the mesh. In both cases, we'll annotate the namespace for autoinjection:

kubectl annotate ns emissary linkerd.io/inject=enabled
kubectl annotate ns faces linkerd.io/inject=enabled

Then we'll do a rollout restart so that Linkerd can inject its proxy sidecar into all the Pods.

kubectl rollout restart -n emissary deployment
kubectl rollout restart -n faces deployment

Finally, we'll wait for the new Pods to all be ready:

kubectl rollout status -n emissary deployment
kubectl rollout status -n faces deployment

OK! At this point, everything should be happily meshed, so let's point a couple of web browsers to http://localhost/faces/, to make sure that the Faces demo is running.

One browser should be completely normal; the other should use an extension like ModHeader to add the header X-Faces-User: testuser to its requests. Both should show the same thing right now: a bunch of smiley faces on green backgrounds. The one using ModHeader should also say "User: testuser" at the top.

Canary routing

The simplest sort of dynamic request routing we can do is the canary: route a small fraction of traffic destined for a workload to a new version of the workload, so you can make sure the new version works without destroying the user experience if it doesn't. Here's a simple way to do that using an HTTPRoute:

bat k8s/02-canary/color-canary.yaml

If we apply this, we'll see 10% of the color traffic go to color2, which will return blue, instead of green.

kubectl apply -f k8s/02-canary/color-canary.yaml

We can edit the weights to change the distribution of traffic: for example, if we edit the weights so that both are weight: 50, we'll get an even split between green and blue.

kubectl edit -n faces httproute/color-canary

If we edit one of the backends to have weight: 0, that backend will get no traffic. (We could also delete the backendRef entry entirely.) So it's easy for us to make all the backgrounds blue with another kubectl edit.

kubectl edit -n faces httproute/color-canary

A/B Tests

Another straightforward type of dynamic request routing we can do is A/B testing. Here, rather than the random distribution of requests we saw with the canary, we instead use some characteristic of the request to choose where to route the request.

We'll do an A/B test with the X-Faces-User header and the smiley service: any request with X-Faces-User: testuser will see the heart-eyes smiley (😍) instead of the "normal" smiley face (😃). Our browser windows show the value they're sending for X-Faces-User above the grid of smilies ("unknown" means no header is being sent). Both browsers currently show the same smiley.

Here's the HTTPRoute that causes the A/B test to happen:

bat k8s/03-abtest/smiley-ab.yaml

When we apply this, we'll continue to see "normal" smilies from our first browser, but our second will show the heart-eyes smiley:

kubectl apply -f k8s/03-abtest/smiley-ab.yaml

When the A/B test is done, if we want, we can easily edit the HTTPRoute to give everyone heart eyes:

kubectl edit -n faces httproute/smiley-a-b

Sneak Peek: Linkerd 2.13

And there you have it! You can find the source for this workshop at

https://github.com/BuoyantIO/service-mesh-academy

in the sneak-peek-2-13 directory.

As always, we welcome feedback! Join us at https://slack.linkerd.io/ for more.