HiveMQ and Docker

The popularity of Docker for deploying all kinds of applications and services in a containerized environment has been increasing exponentially.
That’s not surprising since orchestration platforms such as Kubernetes, Docker Swarm and Mesos keep improving functionality for managing containers.
The ability to integrate Docker with different cloud infrastructures (think load balancers, block storage) and enterprise grade platforms for bare metal installations makes building complex services from basic container images a breeze.
Recognizing this growing popularity and importance we introduced a continuously updated HiveMQ Docker repository on Docker Hub that can help you streamline your development and deployment efforts.

HiveMQ DockerHub Repository

The HiveMQ DockerHub repository is maintained by the HiveMQ team and provides a single location for the following container images containing select past and current HiveMQ versions of the HiveMQ DNS Discovery Image and the HiveMQ Base Image, which can be used to create Custom HiveMQ Images.

Tags

The following table lists all currently available tags:

Tag Description

latest

This tag will always point to the latest version of the HiveMQ base image

dns-latest

This tag will always point to the latest version of the HiveMQ DNS discovery image

<version>

Base image providing the given version of the broker (e.g. 4.0.0)

dns-<version>

DNS discovery image based on the given version base image

HiveMQ DNS Discovery Image

The HiveMQ DNS Discovery Image comes with the HiveMQ DNS Discovery Extension pre-installed and is optimized for the use with Orchestration software that provided a Round-robin A record DNS service.

Run a HiveMQ Cluster in Docker

To enable a HiveMQ cluster, it is necessary that the HiveMQ nodes are able to find each other, via cluster discovery. We introduced the DNS Discovery Extension that leverages a Round-robin A records DNS service to achieve cluster discovery and is tailor made to fit dockerized, orchestrated deployments. The upcoming sections show how to utilize the HiveMQ DNS Discovery Image with Docker Swarm and Kubernetes respectively.

Docker Swarm HiveMQ Cluster

The following illustrates how to create a containerized HiveMQ Cluster, using the HiveMQ DNS Discovery Image and Docker Swarm.

We do not recommend using Docker Swarm in production

Start a single node Swarm cluster by running:

docker swarm init

Create an overlay network for the cluster nodes to communicate on:

docker network create -d overlay --attachable myNetwork

Create the HiveMQ service on the network, using the latest HiveMQ DNS Discovery Image

docker service create \
  --replicas 3 --network myNetwork \
  --env HIVEMQ_DNS_DISCOVERY_ADDRESS=tasks.hivemq \
  --publish target=1883,published=1883 \
  --publish target=8080,published=8080 \
  -p 8000:8000/udp \
  --name hivemq \
    hivemq/hivemq4:dns-latest

This will provide a 3 node cluster with the MQTT(1883) and Web UI(8080) ports forwarded to the host network.

This means you can connect MQTT clients on port 1883. The connection will be forwarded to any of the cluster nodes.

The HiveMQ Web UI can be used in a single node cluster. A sticky session for the HTTP requests in clusters with multiple nodes cannot be upheld with this configuration, as the internal load balancer forwards requests in an alternating fashion. To use sticky sessions the Docker Swarm Enterprise version is required.

Managing the Cluster

To scale the cluster up to 5 nodes, run

docker service scale hivemq=5

To remove the cluster, run

docker service rm hivemq

To read the logs for all HiveMQ nodes in real time, use

docker service logs hivemq -f

To get the log for a single node, get the list of service containers using

docker service ps hivemq

And print the log using

docker service logs <id>

where <id> is the container ID listed in the service ps command.

Kubernetes HiveMQ Cluster

On Kubernetes, an appropriate deployment configuration is necessary to utilize DNS discovery. A headless service will provide a DNS record for the broker that can be used for discovery.

Following is an example configuration for a HiveMQ cluster with 3 nodes using DNS discovery in a replication controller setup.

You need to replace HIVEMQ_DNS_DISCOVERY_ADDRESS according to your Kubernetes namespace and configured domain.
apiVersion: v1
kind: ReplicationController
metadata:
  name: hivemq-replica
spec:
  replicas: 3
  selector:
    app: hivemq-cluster
  template:
    metadata:
      name: hivemq-cluster
      labels:
        app: hivemq-cluster
    spec:
      containers:
      - name: hivemq-pods
        image: hivemq/hivemq4:dns-latest
        ports:
        - containerPort: 8080
          protocol: TCP
          name: web-ui
        - containerPort: 1883
          protocol: TCP
          name: mqtt
        env:
        - name: HIVEMQ_DNS_DISCOVERY_ADDRESS
          value: "hivemq-discovery.default.svc.cluster.local."
        - name: HIVEMQ_DNS_DISCOVERY_TIMEOUT
          value: "20"
        - name: HIVEMQ_DNS_DISCOVERY_INTERVAL
          value: "21"
        readinessProbe:
          tcpSocket:
            port: 1883
          initialDelaySeconds: 30
          periodSeconds: 60
          failureThreshold: 60
        livenessProbe:
          tcpSocket:
            port: 1883
          initialDelaySeconds: 30
          periodSeconds: 60
          failureThreshold: 60
---
kind: Service
apiVersion: v1
metadata:
  name: hivemq-discovery
  annotations:
    service.alpha.kubernetes.io/tolerate-unready-endpoints: "true"
spec:
  selector:
    app: hivemq-cluster
  ports:
    - protocol: TCP
      port: 1883
      targetPort: 1883
  clusterIP: None

Accessing the Web UI

To access the HiveMQ Web UI for a cluster running on Kubernetes, follow these steps:

Create a service exposing the Web UI of the HiveMQ service. Use the following YAML(web.yaml) definition:

kind: Service
apiVersion: v1
metadata:
  name: hivemq-web-ui
spec:
  selector:
    app: hivemq-cluster
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 8080
  sessionAffinity: ClientIP
  type: LoadBalancer

Create the service using kubectl create -f web.yaml

Depending on your provider of the Kubernetes environment, load balancers might not be available or additional configuration may be necessary to access the Web UI.

Connecting external clients on the MQTT port

To allow access for the MQTT port of a cluster running on Kubernetes, follow these steps:

Create a service exposing the MQTT port using a load balancer. You can use the following YAML(mqtt.yaml) definition:

kind: Service
apiVersion: v1
metadata:
  name: hivemq-mqtt
spec:
  selector:
    app: hivemq-cluster1
  ports:
    - protocol: TCP
      port: 1883
      targetPort: 1883
  type: LoadBalancer

Create the service using kubectl create -f mqtt.yaml

You can now connect MQTT clients via the load balancers external endpoint on port 1883.

Please check out our HiveMQ and Kubernetes blog post for more information and resources.

Environment Variables

The following table lists all available environment variables that can be used for custom configuration of the HiveMQ DNS Discovery Docker container

Environment Variable Default Value Description

HIVEMQ_DNS_DISCOVERY_ADDRESS

-

Address to get the A record that will be used for cluster discovery

HIVEMQ_DNS_DISCOVERY_INTERVAL

31

Interval in seconds after which to search for new nodes

HIVEMQ_DNS_DISCOVERY_TIMEOUT

30

Wait time for DNS resolution in seconds

HIVEMQ_CLUSTER_PORT

8000

Port used for cluster transport

HIVEMQ_LICENSE

-

base64 encoded license file to use for the broker

HIVEMQ_BIND_ADDRESS

-

Cluster transport bind address - only necessary if the default policy (resolve hostname) fails

HIVEMQ_CONTROL_CENTER_USER

admin

Username for the Control Center login

HIVEMQ_CONTROL_CENTER_PASSWORD

SHA256 of adminhivemq

Password for the Control Center login

Adding a HiveMQ License

To add your HiveMQ license to the Docker container you must set the container’s environment variables HIVEMQ_LICENSE to the base64 encoded String of your license file. To base64 encode your license file as a String run this command:

cat path/to/your/hivemq-license.lic | base64

Changing User Credentials for the HiveMQ Control Center

By default the HiveMQ Control Center login credentials are admin:hivemq. If you wish to change those credentials you can use the environment variables HIVEMQ_CONTROL_CENTER_USER and HIVEMQ_CONTROL_CENTER_PASSWORD.

A SHA256 hashed value of your desired password is expected. See Generate a SHA256 Password to read more about how to generate the password hash.

Overriding the Bind Address

By default this image will attempt to set the bind address using the containers ${HOSTNAME} to ensure that HiveMQ will bind the cluster connection to the correct interface so a cluster can be formed.

This behavior can be overridden by setting any value for the environment variable HIVEMQ_BIND_ADDRESS. The broker will attempt to use the given value as the bind address instead.

HiveMQ Base Image

The HiveMQ base image installs and optimizes the HiveMQ installation for execution as a container.

It is meant to be used to build custom images or to run a dockerized HiveMQ locally for testing purposes.

Run a HiveMQ Single Node in Docker

To start a single HiveMQ instance and allow access to the MQTT port as well as the Web UI, get Docker and run the following command:

docker run -p 8080:8080 -p 1883:1883 hivemq/hivemq4:latest

You now have a dockerized local HiveMQ and can connect to the broker (1883) or the Control Center (8080) via the respective ports.

Creating a custom HiveMQ Docker Image

You can build your own image from the provided base image and utilize any of the provided HiveMQ versions. Here is an example of a Dockerfile that does all of the following:

ARG TAG=latest

# (1)
FROM hivemq/hivemq4:${TAG}

# (2)
ENV MY_CUSTOM_PLUGIN_ENV myvalue
# (3)
ENV HIVEMQ_CLUSTER_PORT 8000

# (4)
COPY --chown=hivemq:hivemq your-license.lic /opt/hivemq/license/your-license.lic
COPY --chown=hivemq:hivemq myconfig.xml /opt/hivemq/conf/config.xml
COPY --chown=hivemq:hivemq myextension /opt/hivemq/plugins/myextension
COPY --chown=hivemq:hivemq myentrypoint.sh /opt/myentrypoint.sh

# (5)
RUN chmod +x /opt/myentrypoint.sh

# (6)
ENTRYPOINT ["/opt/myentrypoint.sh"]

This custom image:

  1. Uses the hivemq/hivemq4:latest image as a base, with a build argument that (optionally) specifies which base tag to use.

  2. Defines an environment variable for the plugin.

  3. Defines an environment variable that is substituted in the HiveMQ configuration file on start up. For details, see Using environment variables for configuration.

  4. Copies required files such as a valid HiveMQ license file, a customized configuration, a custom extension folder and custom entry point to the corresponding folders and applies proper ownership inside the container.

  5. Sets the custom entry point as executable.

  6. Defines the entry point for the image. This definition is optional, but it allows you to run additional commands or programs (for configuration purposes) before you start the actual HiveMQ instance.

Here’s a way to build the Dockerfile

docker build --build-arg TAG=4.0.0 -t hivemq-extension .

The result is an image built on the HiveMQ base image version 4.0.0 and the current path as the build context. The finished image is tagged locally as hivemq-myplugin:latest.