Xiaomi Mijia Ble Sensor MQTT on containers on Kubernetes

Nov 8, 2019 13:26 · 724 words · 4 minute read

Intro

As I mentioned in my previous post, everything was working flawlessly… except for a bluetooth issue in my raspberry pi 3 that basically renders bluetooth unusuable… but it is rebooted daily via a cron job, so minor issue :) (I know I know, I’m planning to do a better workaround…)

This was good enough, but a few days ago I decided to give k3sup a chance and install k3s (a lightweight Kubernetes distribution focused on ARM/IoT devices) in a spare pine64 that was gathering dust in a drawer :)

Entering k3s

The process was really straightforward, download the k3sup binary and run it against an already installed raspbian/armbian. Then I decided to add the raspberry pi 3 as a node as well. Again, straightforward procedure, k3sup join and that’s it, I have a k3s cluster:

NAME            STATUS   ROLES    AGE   VERSION
pi3.minwi.lan   Ready    worker   47h   v1.15.4-k3s.1
pine64          Ready    master   2d    v1.15.4-k3s.1

NOTE: Not so straightforward… there is an issue in k3s if using iptables > 1.8 so I’ve created a PR to document the issue in k3sup

So… what to do next? The answer was to move the cron docker run to a proper Kubernetes CronJob… but first, let me introduce multi architecture builds.

Multi Architecture builds

This fancy term basically means that when you pull a image from a container registry, it is smart enough to pull the proper image depending on your CPU architecture (x86_64, arm flavors, etc.), so you can just podman pull myfancyimage:latest and it just simply works.

In order to enable this for the xiaomi-ble-mqtt image, I:

  • Created a compatible multi architecture Dockerfile:
FROM registry.fedoraproject.org/fedora:30

VOLUME /config
WORKDIR /usr/src/app

RUN dnf install glib2-devel make gcc python3-pip -y && \
    pip3 install --no-cache-dir mitemp_bt bluepy paho-mqtt && \
    dnf clean all

RUN groupadd -g 9999 appuser && \
    useradd -r -u 9999 -g appuser appuser && \
    chown appuser.appuser /usr/src/app/
USER appuser

COPY . /usr/src/app/

CMD [ "/usr/src/app/run.sh" ]
  • Built a xiaomi-ble-mqtt:amd64 image in my laptop and pushed it to dockerhub
docker build -t docker.io/myuser/xiaomi-ble-mqtt:amd64 -f contrib/Dockerfile .
docker login
docker push docker.io/myuser/xiaomi-ble-mqtt:amd64
  • Built a xiaomi-ble-mqtt:armv7 image in my rpi3 and pushed it on dockerhub
docker build -t docker.io/myuser/xiaomi-ble-mqtt:armv7 -f contrib/Dockerfile .
docker login
docker push docker.io/myuser/xiaomi-ble-mqtt:armv7
  • Created a multi-arch-manifest.yaml file with the following content:
image: eminguez/xiaomi-ble-mqtt:latest
manifests:
  - image: eminguez/xiaomi-ble-mqtt:amd64
    platform:
      architecture: amd64
      os: linux
  - image: eminguez/xiaomi-ble-mqtt:armv7
    platform:
      architecture: arm
      os: linux
      variant: v7
manifest-tool --username youruser --password yourpassword push from-spec contrib/multi-arch-manifest.yaml

So, you just now simply podman pull eminguez/xiaomi-ble-mqtt:latest and it will get the proper one :)

NOTE: As you may noticed, I’ve mixed docker/podman. I did it just because it seems OCI images pushed to dockerhub don’t show up and aren’t available

I’ve already created a PR to the xiaomi-ble-mqtt with the changes.

Back to the CronJob

Once the builds were properly set, I just needed to create a Kubernetes CronJob to run the container every X minutes… with a few limitations:

  • Bluetooth device must be used by the container (I’ve used hostNetwork and scc privileged… pending to improve this)
  • The config files are stored in a directory (/home/edu/xiaomi-ble-mqtt, pending to move it to a configmap)
  • I don’t want (and cannot) have two process querying the sensors at the same time (concurrencyPolicy: Forbid)
  • I can only use the rpi3 to run the container (use nodeSelector)

With those limitations, this is the CronJob yaml file:

apiVersion: batch/v1beta1
kind: CronJob
metadata:
  name: xiaomi-ble-mqtt
spec:
  concurrencyPolicy: Forbid
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - image: eminguez/xiaomi-ble-mqtt
            imagePullPolicy: Always
            name: xiaomi-ble-mqtt
            securityContext:
              privileged: true
            volumeMounts:
            - mountPath: /config
              name: xiaomi-ble-mqtt-config
          hostNetwork: true
          nodeSelector:
            bluetooth: enabled
          volumes:
          - hostPath:
              path: /home/edu/xiaomi-ble-mqtt/
              type: Directory
            name: xiaomi-ble-mqtt-config
  schedule: '*/5 * * * *'

I’ve labeled the raspberry pi 3 with the ‘bluetooth: enabled’ label and created the CronJob:

kubectl label node/pi3.minwi.lan "bluetooth=enabled"
kubectl get nodes -o wide --show-labels

NAME            STATUS   ROLES    AGE   VERSION         INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                         KERNEL-VERSION   CONTAINER-RUNTIME          LABELS
pi3.minwi.lan   Ready    worker   47h   v1.15.4-k3s.1   192.168.3.109   <none>        Raspbian GNU/Linux 10 (buster)   4.19.66-v7+      containerd://1.2.8-k3s.1   beta.kubernetes.io/arch=arm,beta.kubernetes.io/os=linux,bluetooth=enabled,kubernetes.io/arch=arm,kubernetes.io/hostname=pi3.minwi.lan,kubernetes.io/os=linux,node-role.kubernetes.io/worker=true
pine64          Ready    master   2d    v1.15.4-k3s.1   192.168.3.104   <none>        Debian GNU/Linux 10 (buster)     5.3.8-sunxi64    containerd://1.2.8-k3s.1   beta.kubernetes.io/arch=arm64,beta.kubernetes.io/os=linux,kubernetes.io/arch=arm64,kubernetes.io/hostname=pine64,kubernetes.io/os=linux,node-role.kubernetes.io/master=true

kubectl apply -f cronjob.yaml

Results

kubectl get po
NAME                               READY   STATUS      RESTARTS   AGE
xiaomi-ble-mqtt-1573216800-6frsr   0/1     Completed   0          14m
xiaomi-ble-mqtt-1573217100-nff4l   0/1     Completed   0          9m5s
xiaomi-ble-mqtt-1573217400-v8n9n   0/1     Completed   0          4m3s

kubectl logs xiaomi-ble-mqtt-1573217400-v8n9n
2019-11-08 12:50:45.286570 habitacion  :  {"temperature": 17.7, "humidity": 49.9, "battery": 84}

w00h00!

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