protobuf-NATS-publish-subscribe/

protobuf-NATS-publish-subscribe example

Using NATS (publish/subscribe) as a pipe to send protobuf messages. This is a model for one-to-many communication.

These are my 6 main example of using protobuf,

• protobuf
• protobuf-NATS-publish-subscribe <- You are here
• protobuf-NATS-queue-groups
• protobuf-NATS-queue-groups-request-reply (I like this one)
• protobuf-NATS-request-reply
• protobuf-NATS-request-reply-goroutines

Table of contents,

• OVERVIEW OF NATS ARCHITECTURES
• START YOUR NATS SERVER
• GET NATS GO CLIENT LIBRARY
• PROTOCOL .proto BUFFER FILE
• RUN
• FLOW - HOW DOES IT WORK
• HIGH-LEVEL ILLUSTRATION

Documentation and reference,

• My protobuf cheat sheet
• My NATS cheat sheet
• Official NATS go client library at github

GitHub Webpage

OVERVIEW OF NATS ARCHITECTURES

We have 3 examples using NATS as a pipe. This diagram may help,

START YOUR NATS SERVER

Using NATS as a pipe. First, lets start your NATS server,

nats-server -v
nats-server -DV -p 4222 -a 127.0.0.1

Where -DV is both debug and trace log.

GET NATS GO CLIENT LIBRARY

You must have this library to use go,

go get -v -u github.com/nats-io/nats.go/

PROTOCOL .proto BUFFER FILE

Lets use the same protobuf file messages.proto in all four examples,

message Person {
    string name = 1;
    int32 age = 2;
    string email = 3;
    string phone = 4;
    uint32 count = 5;
}

Compile the protocol buffer file to get the wrappers,

protoc --go_out=. messages.proto

Place wrapper file messages.pb.go in both the client and server directories.

RUN

This example will have a client publish a message every second to NATS and whoever (server) is subscribed will get the message. This is referred to as one-to-many.

I use the term client/server for lack of a better term. I could of used publisher/subscriber.

In separate windows run,

cd client
go run client.go messages.pb.go

cd server
go run server.go messages.pb.go

You can run as many servers as you want and you will see they all get the same message.

FLOW - HOW DOES IT WORK

First you need to connect to the NATS server in go,

nc, err := nats.Connect("nats://127.0.0.1:4222")
defer nc.Close()

Lets look at the entire flow data -> marshal -> snd -> rcv -> unmarshal -> data.

DATA

sndPerson := &Person{
    Name:  "Jeff",
    Age:   20,
    Email: "blah@blah.com",
    Phone: "555-555-5555",
    Count: count,
}

MARSHAL

msg, err := proto.Marshal(sndPerson)

SEND (PUBLISH)

nc.Publish("foo", msg)

RECEIVE (SUBSCRIBE)

NextMsg will block/wait for the next msg with a timeout of 5 seconds.

sub, err := nc.SubscribeSync("foo")
...
msg, err := sub.NextMsg(time.Duration(5) * time.Second)

UNMARSHAL -> DATA

rcvPerson := &Person{}
err = proto.Unmarshal(msg.Data, rcvPerson)

HIGH-LEVEL ILLUSTRATION

This illustration may help show what we did,