NATS supports a form of load balancing using . Subscribers register a queue group name. A single subscriber in the group is randomly selected to receive the message.
Prerequisites
Go, node.js, ruby and the NATS server should be installed.
1. Start the NATS server
nats-server
2. Clone the repositories for each client examples
go get github.com/nats-io/nats.go
git clone https://github.com/nats-io/nats.js.git
git clone https://github.com/nats-io/nats.rb.git
3. Run the Go client subscriber, providing a queue group name
cd $GOPATH/src/github.com/nats-io/nats.go/examples
go run nats-qsub/main.go foo my-queue
4. Install and run the Node client subscriber with queue group name
npm install nats
cd nats.js/examples
node node-sub --queue=my-queue foo
5. Install and run the Ruby client subscriber with queue group name
gem install nats
nats-queue foo my-queue &
6. Run another Go client subscriber without the queue group.
cd $GOPATH/src/github.com/nats-io/nats.go/examples
go run nats-sub/main.go foo
7. Publish a NATS message using the Go client
cd $GOPATH/src/github.com/nats-io/nats.go/examples
go run nats-pub/main.go foo "Hello NATS!"
8. Verify message publication and receipt
You should see that the publisher the message and prints: Published [foo] : 'Hello NATS!'
You should see that only one of the my-queue group subscribers receives the message and prints it. In addition, the Go client subscriber not in the my-queue group should also receive and print the message.
9. Publish another message
go run nats-pub/main.go foo "Hello NATS Again!"
You should see that a different queue group subscriber receives the message this time, chosen at random among the 3 queue group members.
