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ACI Connector for k8s on a Raspberry Pi Cluster

2017-09-12 | #raspberrypi #kubernetes #arm #azure #docker

Running the Azure Container Instances Connector for Kubernetes[1] on a Raspberry Pi Cluster.

1: https://github.com/azure/aci-connector-k8s

One of the most interesting features of Azure Container Instances[2] is the Azure Container Instances Connector for Kubernetes[3]. This adds an ACI "node" to an existing Kubernetes[4] cluster and allows you to deploy pods to it. This "node" will run pods in ACI without having to create or manage and additional Azure VMs, just point-and-shoot a pod at it and it will run with no additional setup required.

2: https://docs.microsoft.com/en-us/azure/container-instances/

3: https://github.com/azure/aci-connector-k8s

4: https://kubernetes.io

By using the ACI Connector for Kubernetes on a Raspberry PI, a cluster can run homogenous ARM containers on-prem, but still have the ability to deploy and manage x86 containers to a cloud provider.

Read more about Azure Container Instances,




Creating an aci-connector-k8s ARM Image for Raspberry Pi

The upstream aci-connector-k8s image is x86 only, but since it's written in typescript it can easily be run on different architectures. To run on a Raspberry Pi k8s cluster, all that is required is building an armhf Docker image.

5: https://thenewstack.io/azure-container-instances-mean-cheaper-agile-container-tools-way/

6: https://thenewstack.io/azure-container-instances-mean-cheaper-agile-container-tools-way/

7: https://docs.microsoft.com/en-us/azure/container-instances/

8: https://docs.microsoft.com/en-us/azure/container-instances/

9: https://azure.microsoft.com/en-us/blog/announcing-azure-container-instances/

10: https://azure.microsoft.com/en-us/blog/announcing-azure-container-instances/

Building a Nodejs ARM Docker Image

> Note: As of 9/12/2017 Docker Hub Official Images support multi-platform[11] and re-building an image for armhf (or arm64, ppc64le, and s390x) is no longer required if using a supported image (currently Debian based only, Alpine based like below still need to be re-built).



11: https://integratedcode.us/2017/09/13/dockerhub-official-images-go-multi-platform/

The aci-connector-k8s Dockerfile[12] uses `node:8.4.0-alpine` as it's base image. While there are some "unofficial" node ARM images, lets create one from a somewhat official repository. This involves finding an armhf Alpine 3.6 image, copying/pasting the node:8.4-alpine Dockerfile[13], replacing the `FROM` with the armhf version of alpine, and building the image.

12: https://github.com/Azure/aci-connector-k8s/blob/master/Dockerfile

13: https://github.com/nodejs/docker-node/blob/17c50cb300581280805a4183524fbf57840f3a7e/8.4/alpine/Dockerfile

There are two ways to build an armhf image,

Build on Raspberry Pi * 100% native build, less likely to run into bugs * Painfully slow due to Raspberry Pi hardware

Cross-build using Docker for Mac[14] or Multiarch[15] * Dramatically speed up builds * Could have unforseen issues due to running in an emulated environment

After first attempting option 1, two hours later and losing the ability to ssh into the Raspberry Pi, option 2 is a much faster approach. Building on a MacBook Pro using the built-in multiarch features of Docker for Mac works well, but is still slow even on a 4 core system. Fortunately Using up a 24-core Packet.net[16] Type 2 bare-metal instance to cross-compile using Multiarch is easy to do too.

14: https://docs.docker.com/docker-for-mac/multi-arch/

15: https://github.com/multiarch

16: https://www.packet.net

> Note: The official Docker images for armhf are arm32v6[17] and arm32v7[18]. These will work natively on a Raspberry Pi, Docker for Mac, Multiarch, and a Linux system with `qemu-*-static support`. For full details on these see my post on cross-building Docker images[19].



17: https://hub.docker.com/r/arm32v6/

18: https://hub.docker.com/r/arm32v7/

19: http://www.ecliptik.com/Cross-Building-and-Running-Multi-Arch-Docker-Images/

A armhf multiarch nodejs Dockerfile[20] was built on the Packet.net Type 2 instance and pushed to Docker hub as `ecliptik/node:8.4.0-alpine-armhf`. This only took a few minutes using the Type 2 instance, much faster than Raspberry Pi or Macbook Pro.

20: https://github.com/ecliptik/dockerfiles/blob/master/node/Dockerfile.alpine.armhf

Example Using Multiarch to re-build a node armhf alpine image,

curl -sSL https://raw.githubusercontent.com/nodejs/docker-node/c044d61e6d02756bb8ed1557b2f0c7a0d7fead6f/8.4/alpine/Dockerfile | sed "s/alpine:3.6/multiarch\/alpine:armhf-v3.6/" > Dockerfile.node.armhf

docker build -f Dockerfile.node.armhf -t ecliptik/node:8.4.0-alpine-armhf .
docker push ecliptik/node:8.4.0-alpine-armhf

Building an aci-connector-k8s ARM Docker Image

Once a nodejs arm-alpine image is created, clone the aci-connector-k8s[21] repositoriy, and update the `Dockerfile` to use the `ecliptik/node:8.4.0-alpine-armhf` image. Additionaly, use the `Dockefile` below to use multi-stage builds for improved image size.

21: https://github.com/Azure/aci-connector-k8s

### Base Image
# Setup up a base image to use in Build and Runtime images
FROM ecliptik/node:8.4.0-alpine-armhf AS base

COPY package.json .

### Build Image
# Installs build dependencies and npm packages
# Creates artifacts to copy into Runtime image
FROM base AS build

# Install build OS packages
RUN set -ex && \
        buildDeps=' \
                make \
                gcc \
                g++ \
                python \
                py-pip \
                curl \
                openssl \
        ' && \
    apk add --no-cache \
       --virtual .build-deps $buildDeps

#Copy application into build image
COPY . .

# Install npm packages
RUN npm install -g
RUN npm install --silent --save-dev -g \
       gulp-cli \

# Compile typescript sources to javascript artifacts
RUN tsc --target es5 connector.ts

### Runtime Image
# Copy artifacts from Build image and setups up entrypoint/cmd to run app
FROM base AS runtime

# Copy artifacts from Build Image
COPY --from=build /app/node_modules ./node_modules
COPY --from=build /app/*.js ./
COPY --from=build /app/LICENSE ./

# Runtime command
CMD ["connector.js"]

With an updated `Dockerfile` in the cloned repo, build the aci-connector-k8s image *on* a Raspberry Pi,

docker build -t ecliptik/aci-connector-k8s:alpine-armhf .
docker push ecliptik/aci-connector-k8s:alpine-armhf

> Note: Trying to build the image on non-native armhf platform like Docker for Mac or Multiarch may result in errors like `"SyntaxError: Unexpected end of JSON input"`. The image only seems to build on native Raspberry Pi or ARM hardware.

Running the ACI Connector

Now that we have a armhf image capable of running on a Raspberry Pi, we can deploy the pod to a Raspberry Pi Kubernetes cluster[22].

22: http://www.ecliptik.com/Raspberry-Pi-Kubernetes-Cluster/

First clone the aci-connector-k8s[23] repository onto the Raspberry Pi cluster master,

23: https://github.com/Azure/aci-connector-k8s

git clone https://github.com/Azure/aci-connector-k8s.git

Edit the `examples/aci-connector.yaml` and update the `image` to use the `ecliptik/aci-connector-k8s:alpine-armhf` image.

Next, if you used `kubeadm` to create your cluster and RBAC is enabled, you'll need to create a role and set it up for the connector. This is discussed in this Github issue[24] that includes creating a RBAC role and updating the service to use it.

24: https://github.com/Azure/aci-connector-k8s/issues/26#issuecomment-326809041

Create the RBAC role for the connector,

curl -sSL https://raw.githubusercontent.com/alexjmoore/aci-connector-k8s-arm/master/aci-connector-rbac.yaml | kubectl create -f -

Under `spec` in the `examples/aci-connector.yaml` add the RBAC role,

serviceAccountName: aci-connector-sa

Finally after the connector is setup to use the armhf image and RBAC, follow the rest of the *Quickstart* guide in the aci-connector-k8s README[25] to set up everything else required to run the connector (Azure keys, deployment of service, etc).

25: https://github.com/Azure/aci-connector-k8s/blob/master/README.md

Working Example

Updated `examples/aci-connector.yaml` with RBAC role and `ecliptik/aci-connector-k8s:alpine-armhf` image

apiVersion: extensions/v1beta1
kind: Deployment
  name: aci-connector
  namespace: default
  replicas: 1
        app: aci-connector
      serviceAccountName: aci-connector-sa
      - name: aci-connector
        image: ecliptik/aci-connector-k8s:alpine-armhf
        imagePullPolicy: Always
        - name: AZURE_CLIENT_ID
          value: 00000-000-00000-0000-0000
        - name: AZURE_CLIENT_KEY
          value: 00000-000-00000-0000-0000
        - name: AZURE_TENANT_ID
          value: 00000-000-00000-0000-0000
          value: 100000-000-00000-0000-0000
        - name: ACI_RESOURCE_GROUP
          value: aci-test

Deploy the aci-connector pod,

kubectl create -f examples/aci-connector.yaml

Wait a few minutes while the pod comes into service (mostly waiting for the image to pull) on a worker node.

Verify aci-connector pod has started,

kubectl get pods
NAME                             READY     STATUS    RESTARTS   AGE
aci-connector-1252680567-b88w6   1/1       Running   0          3m

Verify aci-connector node is added,

kubectl get nodes -o wide
NAME            STATUS    AGE       VERSION   EXTERNAL-IP   OS-IMAGE                        KERNEL-VERSION
aci-connector   Ready     2m        v1.6.6    <none>        <unknown>                       <unknown>
navi            Ready     1h        v1.7.5    <none>        Raspbian GNU/Linux 8 (jessie)   4.4.50-hypriotos-v7+
tael            Ready     1h        v1.7.5    <none>        Raspbian GNU/Linux 8 (jessie)   4.4.50-hypriotos-v7+
tatl            Ready     1h        v1.7.5    <none>        Raspbian GNU/Linux 8 (jessie)   4.4.50-hypriotos-v7+

Deploy `example/nginx-pod.yaml` pod from aci-connector-k8s repo,

kubectl create -f examples/nginx-pod.yaml
pod "nginx" created

Verify pod deployed and is running in ACI,

kubectl get pods -o wide
 NAME                             READY     STATUS    RESTARTS   AGE       IP               NODE
 aci-connector-1696751608-tcjcq   1/1       Running   0          24m       tael
 nginx                            1/1       Running   0          10s   aci-connector

General Docker on ARM Links

While researching and setting this up I came across many good resources on running Docker on ARM,





ARM Docker Image Repositories

26: https://help.packet.net/armv8/docker-on-armv8

27: https://help.packet.net/armv8/docker-on-armv8

28: https://github.com/docker-library/official-images#architectures-other-than-amd64

29: https://github.com/docker-library/official-images#architectures-other-than-amd64

30: https://blog.hypriot.com/post/first-touch-down-with-docker-for-mac/

31: https://blog.hypriot.com/post/first-touch-down-with-docker-for-mac/

32: https://resin.io/blog/building-arm-containers-on-any-x86-machine-even-dockerhub/

33: https://resin.io/blog/building-arm-containers-on-any-x86-machine-even-dockerhub/

arm32v6[34] - Works on RPI 3 with HypriotOS[35] 32-bit

arm32v7[36] - Works on RPI 3 with HypriotOS[37] 32-bit

arm64v8[38] - Currently no 64-bit version of HypriotOS, but will work on Packet.net Type 2A Instances[39]









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