Crossbar Image with Consul Service Discovery

This is a docker container that is intended to be used to in a micro services architecture in conjunction with Consul to dynamically discover the Crossbar.io router.

Usage

To use this image, do the following

Dockerfile

Create a Dockerfile

FROM thehq/crossbar-service-consul

COPY src/ app/src/

Run Docker

Execute Docker overriding the following environment variables as necessary

• SERVICE_ENTRY (default=src.app_session.AppSession): The python path to your application session
• ROUTER_PROTOCOL (default=ws): The protocol to use
• ROUTER_SERVICE (default=app.router): The name of your Crossbar Router service in Consul
• ROUTER_REALM (default=realm1): The name of the realm
• CONSUL_SERVER (default=consul.service.consul:8500): The address of your Consul Server

An example of overriding the CONSUL_SERVER and ROUTER_REALM variables

docker run \
  -e "CONSUL_SERVER=localhost:8500" \
  -e "ROUTER_REALM=main" ...

Details

This Docker Image has the following features

• Runs the application session using a Crossbar.io worker container (see templates/config.json.tmpl)
• Runs "crossbar start" inside of a runit daemon (see services/connect/run)
• Runs Consul Template inside of a runit daemon (see services/config/run)

The result is a service that will reconfigure itself as it dynamically discovers the address of the application router.

Other Customization

You can also leverage Consul Template for other things

Reconfigure Service Based on Consul Key/Value Store

Lets say you are using Consul to store some configuration information that your application depends on and you would like to restart the service whenever that information changes, you can do the following

Assumptions:

• File is called "data.json" and is read by the code from the run directory, which for this example is in "/app/.crossbar/" inside the container
• The Consul Key where this data is stored is at "$CONSUL_APP_DATA_PATH + '/data'"

Update the following files

templates/data.json.tmpl

{{ key (print (env "CONSUL_APP_DATA_PATH") "/data") }}

services/data/run

#!/bin/bash

cat /etc/consul-templates/data.json.tmpl

exec consul-template \
  -consul=$CONSUL_SERVER \
  -template "/etc/consul-templates/data.json.tmpl:/app/.crossbar/data.json:cat /app/.crossbar/data.json; sv restart connect"

Dockerfile

FROM thehq/crossbar-service-consul

RUN mkdir /etc/consul-templates/
COPY templates/*.tmpl /etc/consul-templates/

# Copy any source code
COPY src/ /app/src/

# Create the services
COPY services/ /etc/service/
RUN chmod +x /etc/service/*/run

Initialize the Consul Key/Value store and run.

License

MIT