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Explore NATS Queueing
NATS supports a form of load balancing using queue groups. 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

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nats-server
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2. Clone the repositories for each client examples

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go get github.com/nats-io/nats.go
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git clone https://github.com/nats-io/nats.js.git
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git clone https://github.com/nats-io/nats.rb.git
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3. Run the Go client subscriber, providing a queue group name

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cd $GOPATH/src/github.com/nats-io/nats.go/examples
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go run nats-qsub/main.go foo my-queue
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4. Install and run the Node client subscriber with queue group name

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npm install nats
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cd nats.js/examples
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node node-sub --queue=my-queue foo
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5. Install and run the Ruby client subscriber with queue group name

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gem install nats
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nats-queue foo my-queue &
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6. Run another Go client subscriber without the queue group.

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cd $GOPATH/src/github.com/nats-io/nats.go/examples
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go run nats-sub/main.go foo
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7. Publish a NATS message using the Go client

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cd $GOPATH/src/github.com/nats-io/nats.go/examples
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go run nats-pub/main.go foo "Hello NATS!"
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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

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go run nats-pub/main.go foo "Hello NATS Again!"
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You should see that a different queue group subscriber receives the message this time, chosen at random among the 3 queue group members.
Last modified 1yr ago