Register services running on Docker containers

This topic provides an overview for registering services running on Docker containers in Consul.

Register a service

Start a service in a container and register it with the Consul client. The following examples refer to a counting-service that increments a number every time it is accessed and then returns that number.

Pull the container.

$ docker pull hashicorp/counting-service:0.0.2

Run the container with port forwarding so that you can access it from your web browser by visiting http://localhost:9001.

$ docker run \
   -p 9001:9001 \
   -d \
   --name=counting-service \
   hashicorp/counting-service:0.0.2

Next, create a service definition to register the counting service with the Consul client.

{
   "service": {
      "name": "counting",
      "tags": ["go"],
      "port": 9001
   }
}

Create the /consul/config/counting.json file in a container where a Consul service runs. In the following example, this container is the consul-client container.

$ docker exec consul-client /bin/sh -c "echo '{\"service\": {\"name\": \"counting\", \"tags\": [\"go\"], \"port\": 9001}}' >> /consul/config/counting.json"

Because the Consul client does not automatically detect changes in the configuration directory, you must issue a reload command to the same container. Consul cannot register the service until you trigger a configuration reload.

$ docker exec consul-client consul reload
Configuration reload triggered

In the logs of the consul-client container, you can find entries that confirm that the Consul client received the hangup signal, reloaded its configuration, and synced the counting service.

2022-12-15T19:02:24.945Z [INFO]  agent: Synced service: service=counting