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NATS and Docker

NATS Server Containerization

The NATS server is provided as a Docker image on Docker Hub that you can run using the Docker daemon. The NATS server Docker image is extremely lightweight, coming in under 10 MB in size.

Synadia actively maintains and supports the NATS server Docker image.

Nightly

The nightly build container can be found here

Usage

To use the Docker container image, install Docker and pull the public image:

docker pull nats

Run the NATS server image:

docker run nats

By default the NATS server exposes multiple ports:

  • 4222 is for clients.

  • 8222 is an HTTP management port for information reporting.

  • 6222 is a routing port for clustering.

The default ports may be customized by providing either a -p or -P option on the docker run command line.

The following steps illustrate how to run a server with the ports exposed on a docker network.

First, create the docker network 'nats:'

Then start the server:

Creating a NATS Cluster

First, run a server with the ports exposed on the 'nats' docker network:

Next, start additional servers pointing them to the seed server to cause them to form a cluster:

NOTE Since the Docker image protects routes using credentials we need to provide them above. Extracted from Docker image configuration

To verify the routes are connected, you can make a request to the monitoring endpoint on /routez and confirm that there are now 2 routes:

Creating a NATS Cluster with Docker Compose

It is also straightforward to create a cluster using Docker Compose. Below is a simple example that uses a network named 'nats' to create a full mesh cluster.

Now we use Docker Compose to create the cluster that will be using the 'nats' network:

Testing the Clusters

Now, the following should work: make a subscription on one of the nodes and publish it from another node. You should be able to receive the message without problems.

Inside the container:

Stopping the seed node, which received the subscription, should trigger an automatic failover to the other nodes:

Output extract:

Publishing again will continue to work after the reconnection:

Tutorial

See the NATS Docker tutorial for more instructions on using the NATS server Docker image.

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