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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.

Usage

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

> docker pull nats

Run the NATS server image:

> docker run -d --name nats-main 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.
  • Use -p or -P to customize.

For example:

$ docker run -d --name nats-main nats
[INF] Starting nats-server version 0.6.6
[INF] Starting http monitor on port 8222
[INF] Listening for route connections on 0.0.0.0:6222
[INF] Listening for client connections on 0.0.0.0:4222
[INF] nats-server is ready

To run with the ports exposed on the host:

> docker run -d -p 4222:4222 -p 6222:6222 -p 8222:8222 --name nats-main nats

To run a second server and cluster them together:

> docker run -d --name=nats-2 --link nats-main nats --routes=nats-route://ruser:T0pS3cr3t@nats-main:6222

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

# Routes are protected, so need to use them with --routes flag
# e.g. --routes=nats-route://ruser:T0pS3cr3t@otherdockerhost:6222
authorization {
  user: ruser
  password: T0pS3cr3t
  timeout: 2
}

To verify the routes are connected:

$ docker run -d --name=nats-2 --link nats-main nats --routes=nats-route://ruser:T0pS3cr3t@nats-main:6222 -DV
[INF] Starting nats-server version 2.0.0
[INF] Starting http monitor on port 8222
[INF] Listening for route connections on :6222
[INF] Listening for client connections on 0.0.0.0:4222
[INF] nats-server is ready
[DBG] Trying to connect to route on nats-main:6222
[DBG] 172.17.0.52:6222 - rid:1 - Route connection created
[DBG] 172.17.0.52:6222 - rid:1 - Route connect msg sent
[DBG] 172.17.0.52:6222 - rid:1 - Registering remote route "ee35d227433a738c729f9422a59667bb"
[DBG] 172.17.0.52:6222 - rid:1 - Route sent local subscriptions

Clustering With Docker

Below is are a couple examples of how to setup nats-server cluster using Docker. We put 3 different configurations (one per nats-server server) under a folder named conf as follows:

|-- conf
    |-- nats-server-A.conf
    |-- nats-server-B.conf
    |-- nats-server-C.conf

Each one of those files have the following content below: (Here I am using ip 192.168.59.103 as an example, so just replace with the proper ip from your server)

Example 1: Setting up a cluster on 3 different servers provisioned beforehand

In this example, the three servers are started with config files that know about the other servers.

nats-server-A

# Cluster Server A

port: 7222

cluster {
  host: '0.0.0.0'
  port: 7244

  routes = [
    nats-route://192.168.59.103:7246
    nats-route://192.168.59.103:7248
  ]
}

nats-server-B

# Cluster Server B

port: 8222

cluster {
  host: '0.0.0.0'
  port: 7246

  routes = [
    nats-route://192.168.59.103:7244
    nats-route://192.168.59.103:7248
  ]
}

nats-server-C

# Cluster Server C

port: 9222

cluster {
  host: '0.0.0.0'
  port: 7248

  routes = [
    nats-route://192.168.59.103:7244
    nats-route://192.168.59.103:7246
  ]
}

To start the containers, on each one of your servers, you should be able to start the nats-server image as follows:

docker run -it -p 0.0.0.0:7222:7222 -p 0.0.0.0:7244:7244 --rm -v $(pwd)/conf/nats-server-A.conf:/tmp/cluster.conf nats -c /tmp/cluster.conf -p 7222 -D -V
docker run -it -p 0.0.0.0:8222:8222 -p 0.0.0.0:7246:7246 --rm -v $(pwd)/conf/nats-server-B.conf:/tmp/cluster.conf nats -c /tmp/cluster.conf -p 8222 -D -V

docker run -it -p 0.0.0.0:9222:9222 -p 0.0.0.0:7248:7248 --rm -v $(pwd)/conf/nats-server-C.conf:/tmp/cluster.conf nats -c /tmp/cluster.conf -p 9222 -D -V

Example 2: Setting a nats-server cluster one by one

In this scenario:

  • We bring up A and get its ip (nats-route://192.168.59.103:7244)
  • Then create B and then use address of A in its configuration.
  • Get the address of B nats-route://192.168.59.104:7246 and create C and use the addresses of A and B.

First, we create the Node A and start up a nats-server server with the following config:

# Cluster Server A

port: 4222

cluster {
  host: '0.0.0.0'
  port: 7244

}

docker run -it -p 0.0.0.0:4222:4222 -p 0.0.0.0:7244:7244 --rm -v $(pwd)/conf/nats-server-A.conf:/tmp/cluster.conf nats -c /tmp/cluster.conf -p 4222 -D -V

Then we proceed to create the next node. We realize that the first node has ip:port as 192.168.59.103:7244 so we add this to the routes configuration as follows:

# Cluster Server B

port: 4222

cluster {
  host: '0.0.0.0'
  port: 7244

  routes = [
    nats-route://192.168.59.103:7244
  ]
}

Then start server B:

docker run -it -p 0.0.0.0:4222:4222 -p 0.0.0.0:7244:7244 --rm -v $(pwd)/conf/nats-server-B.conf:/tmp/cluster.conf nats -c /tmp/cluster.conf -p 4222 -D -V

Finally, we create another Node C. We now know the routes of A and B so we can add it to its configuration:

# Cluster Server C

port: 4222

cluster {
  host: '0.0.0.0'
  port: 7244

  routes = [
    nats-route://192.168.59.103:7244
    nats-route://192.168.59.104:7244
  ]
}

Then start it:

docker run -it -p 0.0.0.0:4222:4222 -p 0.0.0.0:7244:7244 --rm -v $(pwd)/conf/nats-server-C.conf:/tmp/cluster.conf nats -c /tmp/cluster.conf -p 9222 -D -V

Testing the Clusters

Now, the following should work: make a subscription to Node A then publish to Node C. You should be able to to receive the message without problems.

nats-sub -s "nats://192.168.59.103:7222" hello &

nats-pub -s "nats://192.168.59.105:7222" hello world

[#1] Received on [hello] : 'world'

# nats-server on Node C logs:
[1] 2015/06/23 05:20:31.100032 [TRC] 192.168.59.103:7244 - rid:2 - <<- [MSG hello RSID:8:2 5]

# nats-server on Node A logs:
[1] 2015/06/23 05:20:31.100600 [TRC] 10.0.2.2:51007 - cid:8 - <<- [MSG hello 2 5]

Tutorial

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