Dom Barker
Dec 24, 2017 · 8 min read
every microservices diagram ever

It’s not a microservices platform if there’s only one service. And all those services need to be able to talk to each other, they need to cope when some of them are not feeling well, they need to run on real machines, they need to be able to connect with the outside world and so much more besides.

This is where Kubernetes comes in — it orchestrates the life and times of individual Docker containers, giving us the primitives we need to construct robust and scalable systems.

These microservices things are kind of a big deal right now but there are few step by step guides to getting a basic system up and running. This is partly due to the fact that the notion of a “basic microservice system” is an oxymoron. We’ll try regardless.

We do need some pre requisite knowledge, specifically what Docker is and what it’s for. After that you’ll need to know the Kube fundamentals: Pods, Services, Deployments et al.

This guide is mainly aimed at people who have got a single service running in Kube and are thinking “now what?”.

Tldr; section

If you are more of a ‘just show me the code’ sort of person, you’ll really like this git repo. Otherwise read on.

Before we start

All our microservices will be written in node.js v8.x so you’ll want to go install that first. They’ll all be very simple so you won’t need more than the most cursory javascript / node knowledge.

We’re going to run all this on Minikube, it’s a neat way of getting Kube running locally. You can find installation instructions here. After that you’ll want to verify that your Minikube installation is all good.

First create a Minikube cluster:

$ minikube startStarting local Kubernetes v1.8.0 cluster...
Starting VM...
Getting VM IP address...
Moving files into cluster...
Setting up certs...
Connecting to cluster...
Setting up kubeconfig...
Starting cluster components...
Kubectl is now configured to use the cluster.
Loading cached images from config file.

Then check that the Kube system services are all happy:

$ kubectl get services -n kube-systemNAME                   CLUSTER-IP      EXTERNAL-IP   PORT(S)         AGE
kube-dns 10.96.0.10 <none> 53/UDP,53/TCP 1m
kubernetes-dashboard 10.107.19.167 <nodes> 80:30000/TCP 1m

One more thing, we need Minikube to share our local docker registry, else it won’t be able to find the docker images that we build.

$ eval $(minikube docker-env)

Super. Now let’s build something fun.

TOTAL INVOICE MANAGEMENT!!!1!

Lets build a system that manages invoices for a company. Sounds simple enough and it’s also the most fun thing I could think of. Our system will comprise of:

  • An API gateway to route traffic into our system
  • An authentication service to limit access
  • A front end invoices service to return information about invoices
  • A back end expected date service that’ll tell us when an invoice is likely to be paid
the basics

The first step is getting our folder structure sorted. We’ll have one folder for all our kube config files, and others for each of our services.

- total_invoice_managment
|
| - kube
| - invoices_svc

The invoices service

Our first service is invoices_svc which is responsible for individual invoices. It’ll have a single endpoint api/invoices/:id which will swap an id for the invoice data. Lets quickly scaffold the service using the node package manager (npm).

$ cd ./invoices_svc
$ npm init
# then say yes to everything
$ npm install express

Update package.json to include the script to boot the app:

Add the index.js file that contains the code for the service:

Verify that it runs locally:

$ PORT=3007 npm startinvoices_svc listening on 3007$ curl localhost:3007/api/invoices/10{"id":10,"ref":"INV-10","amount":1000,"balance":990,"ccy":"GBP"}

It works! Satisfied that our service works as expected, we can now dockerize it by making a Dockerfile:

Then we can build the Docker container to make sure all is well:

$ docker build ./ -t invoices_svc:v1

Time to start on getting this service into Kube. Lets change directory to the kube folder a level up:

$ cd ../kube

And add our first bit of kube config. Call the file invoices_svc.yaml

This config defines a Kube service and it’s accompanying deployment. We can ask kube to boot it up

$ kubectl apply -f ./invoices_svc.yamldeployment "invoices-svc" created
service "invoices-svc" created

We should see its service:

$ kubectl get servicesNAME           CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
invoices-svc 10.104.86.220 <none> 80/TCP 3m
kubernetes 10.96.0.1 <none> 443/TCP 1h

And all the pods too:

$ kubectl get podsNAME                            READY     STATUS    RESTARTS   AGE
invoices-svc-65b5f7bbd4-ckr8d 1/1 Running 0 44s
invoices-svc-65b5f7bbd4-gvk9s 1/1 Running 0 44s
invoices-svc-65b5f7bbd4-z2kx7 1/1 Running 0 44s

As there’s no external IP for invoices_svc we’ll need to get into a container inside the cluster to be able to try it out. Spinning one up specially seems odd, but it’s a very kubey way of doing things. Busyboxplus is just a container that has a basic shell and some common tools. We need it to use curl.

$ kubectl run curl --image=radial/busyboxplus:curl -i --tty[ root@curl-696777f579-qwjcr:/ ]$ curl 10.104.86.220/api/invoices/1{"id":1,"ref":"INV-1","amount":100,"balance":90,"ccy":"GBP"}

(To escape the container you need to press ctl-d)

It works! Sort of. It’s pretty useless being stuck inside our cluster - we need to create an ingress so that traffic can find it’s way in. We are going to use Ambassador for this. It’s a handy wrapper around Envoy Proxy and has lots of great API gateway features built in. Routing seems like a good place to start.

We’ll need to get Ambassador running on our cluster. Create a file called ambassador.yaml in the kube folder:

And then we can boot it up:

$ kubectl apply -f ./ambassador.yaml$ kubectl get services
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ambassador 10.103.215.136 <pending> 80:32005/TCP 11s
ambassador-admin 10.104.3.82 <nodes> 8877:31385/TCP 11s
invoices-svc 10.104.86.220 <none> 80/TCP 45m
kubernetes 10.96.0.1 <none> 443/TCP 2h

We need to tell ambassador about our invoices_svc though, and we do so by adding some annotations to theService section of invoices_svc.yaml

The prefix key routes traffic from /invoices/ to our service. To keep things nice and tidy the rewrite key does a bit of transforming too so that traffic to /invoices/:id gets routed to our service at /api/invoices/:id.

Once the config has been added, we can apply it:

$ kubectl apply -f ./invoices_svc.yaml

Ambassador keeps watch over everything that happens in the cluster. When we updated the config, ambassador detected that change and went looking for any annotations. It found them, and will now route traffic to the service.

In theory, we now have a working external api gateway to our cluster. Before we can validate that hypothesis we need to create a tunnel from our localhost to the minikube cluster:

$ minikube service ambassador --urlhttp://192.168.99.100:32005

This particular url is only for my local machine — you need to use your own for future steps.

We can use the returned url to reach our cluster:

$ curl http://192.168.99.100:32005/invoices/42{"id":42,"ref":"INV-42","amount":4200,"balance":4190,"ccy":"GBP"}

🎉 It works! So we have a service and a gateway.

Adding authentication

It’s not great having our service available to world + dog. We should add some kind of authentication to our gateway. Nobody will be surprised to hear that we’ll want a new service for that, or that it’ll be called auth_svc.

  • Create a new folder called auth_svc
  • Copy the Dockerfile from invoices_svc
  • Repeat the npm steps that we did for invoices_svc
$ cd ../
$ mkdir auth_svc
$ cd ./auth_svc
$ npm init
$ npm install express
$ cp ../invoices_svc/Dockerfile .
# don't forget to add "start": "node index.js" to your package.json!
  • Create the auth_svc app:
  • Create the kube config:
  • Build the docker image:
$ docker build -t auth_svc:v1 ./auth_svc/
  • Apply the kube config:
$  kubectl apply -f ./kube/auth_svc.yaml
  • see if it worked:
$ curl http://192.168.99.100:32005/invoices/42{"ok":false}

Aces, we are now locked out, unless we know the magic word:

$  curl http://192.168.99.100:32005/invoices/42 -H 'authorization: letmeinpleasekthxbye'{"id":42,"ref":"INV-42","amount":4200,"balance":4190,"ccy":"GBP"}

Let’s take stock. We have an API gateway that authenticates traffic and routes it to our service. However we don’t want all of our services to be public, what about back end services that our front end services call? Well, Kube has a way of doing that too.

When do I get paid?

It’s always nice to know when your customers will pay you. We will create an extreme high sophistication algorithmic inference engine* that’ll tell us when an invoice is expected to be paid. It’s a similar jig to the last two services:

$ cd ../
$ mkdir expected_date_svc
$ cd ./expected_date_svc
$ npm init
$ npm install express
$ npm install moment
$ cp ../invoices_svc/Dockerfile .
# don't forget to add "start": "node index.js" to your package.json!

And the extreme high sophistication algorithmic inference engine code is:

That just leaves the kube config:

You know the drill:

$ docker build -t expected_date_svc:v1 .
$ kubectl apply -f ../kube/expected_date_svc.yaml
$ kubectl get services
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
ambassador 10.103.215.136 <pending> 80:32005/TCP 19h
ambassador-admin 10.104.3.82 <nodes> 8877:31385/TCP 19h
auth-svc 10.108.119.134 <none> 3000/TCP 18h
expected-date-svc 10.101.227.50 <none> 80/TCP 1m
invoices-svc 10.104.86.220 <none> 80/TCP 20h
kubernetes 10.96.0.1 <none> 443/TCP 21h

So now we have the expected_date_svc running, we’ll want to modify the invoices_svc to make us of it.

There’s a new dependency we need to make a http request:

$ cd ../invoices_svc
$ npm install request-promise
$ npm install request

Then we make a request to the expected_date_svc and add the result to our invoice object. Here’s the updated invoice_svc:

We need to rebuild the docker image:

$ docker build -t invoices_svc:v2 .

And we also need to update the kube config for the invoices_svc

First up, it needs to reference the new docker image:

We also need to add an environment variable that contains the url to the expected_svc. This is the nifty bit. Kubernetes uses internal DNS routing — you can read more about that here. The short version is that kube creates a special url for every named service. Its format is SVCNAME.NAMESPACE.svc.cluster.local, so the expected_date_svc can be found at expected-date-svc.default.svc.cluster.local. Lets go set that environment variable by updating the config:

Now that the config is all updated, we apply it to the cluster:

$ kubectl apply -f ../kube/invoices_svc.yaml

And check that the expected date is being added:

$ curl http://192.168.99.100:32005/invoices/42 -H 'authorization: letmeinpleasekthxbye'{"id":42,"ref":"INV-42","amount":4200,"balance":4190,"ccy":"GBP","expectedDate":"2018-01-01T11:54:30.769Z"}

This should be enough for the reader to get a cluster running. Next steps include adding and removing replicas to scale services, adding a liveness probe so that kubernetes knows if a service fails silently or logging and monitoring so we can find out what our services are up to when we aren’t looking.

How all the bits go togther

I like it!

Great, us too. We like kube so much that we use it for our most demanding infrastructure requirements at Fluidly, in particular for our data science models. It’s a steep learning curve, but the rewards are substantial.

If you like the sound of this sort of work we are often looking for amazing people. Drop us a line: jobs@fluidly.com .


* our data scientists do this for real!

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Dom Barker

Written by

At work I turn people into teams that turn coffee into code. I spend my free time falling off bicycles.

HackerNoon.com

how hackers start their afternoons.

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