Emitter is a distributed, scalable and fault-tolerant publish-subscribe platform built with MQTT protocol and featuring message storage, security, monitoring and more:

• Publish/Subscribe using MQTT over TCP or Websockets.
• Resilient, highly available and partition tolerant (AP in CAP terms).
• Able to handle 3+ million of messages/sec on a single broker.
• Supports message storage with history and message-level expiry.
• Provides secure channel keys with permissions and can face the internet.
• Automatic TLS/SSL and encrypted inter-broker communication.
• Built-in monitoring with Prometheus, StatsD and more.
• Shared subscriptions, links and private links for channels.
• Easy deployment with Docker and Kubernetes of production-ready clusters.

Emitter can be used for online gaming and mobile apps by satisfying the requirements for low latency, binary messaging and high throughput. It can also be used for the real-time web application such as dashboards or visual analytics or chat systems. Moreover, Emitter is perfect for the internet of things and allows sensors to be controlled and data gathered and analyzed.

The following video tutorials demonstrate various features of Emitter in action.

The quick way to start an Emitter broker is by using docker run command as shown below.

Notice: You must use -e for docker environment.You could get it from your docker log.

docker run -d --name emitter -p 8080:8080 --restart=unless-stopped emitter/server

Alternatively, you can build and run from source.

# install git and go
# depending on your system, you may also need to install gcc and musl-dev
git clone https://github.com/emitter-io/emitter
cd emitter
go get -x .
go build -x .
./emitter

Both commands above start a new server and if no configuration or environment variables were supplied, it will print out a message(or you could find it in the docker log) similar to the message below once the server has started :

[service] unable to find a license, make sure 'license' value is set in the config file or EMITTER_LICENSE environment variable
[service] generated new license: uppD0PFIcNK6VY-7PTo7uWH8EobaOGgRAAAAAAAAAAI
[service] generated new secret key: JUoOxjoXLc4muSxXynOpTc60nWtwUI3o

This message shows that a new security configuration was generated, you can then re-run EMITTER_LICENSE set to the specified value. Alternatively, you can set "license" property in the emitter.conf configuration file.

References are available. Please replace your EMITTER_LICENSE to it.

docker run -d --name emitter -p 8080:8080 -e EMITTER_LICENSE=uppD0PFIcNK6VY-7PTo7uWH8EobaOGgRAAAAAAAAAAI --restart=unless-stopped emitter/server

Finally, open a browser and navigate to http://127.0.0.1:8080/keygen in order to generate your key. Now you can use the secret key generated to create channel keys, which allow you to secure individual channels and start using emitter.

Warning: If you use upon command, you secret is JUoOxjoXLc4muSxXynOpTc60nWtwUI3o. And it's not safe!!!

The code below shows a small example of usage of emitter with the Javascript SDK. As you can see, the API exposes straightforward methods such as publish and subscribe which can take binary payload and are secured through channel keys.

// connect to emitter service
var connection = emitter.connect({ host: '127.0.0.1' });

// once we're connected, subscribe to the 'chat' channel
emitter.on('connect', function(){
    emitter.subscribe({
        key: "<channel key>",
        channel: "chat"
    });
});

// publish a message to the chat channel
emitter.publish({
    key: "<channel key>",
    channel: "chat/my_name",
    message: "hello, emitter!"
});

Further documentation, demos and language/platform SDKs are available in the develop section of our website. Make sure to check out the getting started tutorial which explains the basic usage of emitter and MQTT.

The Emitter broker accepts command line arguments, allowing you to specify a configuration file, usage is shown below.

-config string
   The configuration file to use for the broker. (default "emitter.conf")

-help
   Shows the help and usage instead of running the broker.

The configuration file (defaulting to emitter.conf) is the main way of configuring the broker. The configuration file is however, not the only way of configuring it as it allows a multi-level override through environment variables and/or hashicorp Vault.

The configuration file is in JSON format, but you can override any value by providing an environment variable which follows a particular format, for example if you'd like to provide a license through environment variable, simply define EMITTER_LICENSE environment variable, similarly, if you want to specify a certificate, define EMITTER_TLS_CERTIFICATE environment variable. Example of configuration file:

{
    "listen": ":8080",
    "license": "/*The license*/",
    "tls": {
        "listen": ":443",
        "host": "example.com"
    },
    "cluster": {
        "listen": ":4000",
        "seed": " 192.168.0.2:4000",
        "advertise": "public:4000"
    },
    "storage": {
        "provider": "inmemory"
    }
}

The structure of the configuration is described below:

The server requires Golang 1.9 to be installed. Once you have this installed, simply go get this repository and run the following commands to download the package and run the server.

go get -u github.com/emitter-io/emitter && emitter

If you want to run the tests, simply run go test command as demonstrated below.

go test ./...

Emitter is conveniently packaged as a docker container. To run the emitter service on a single server, use the command below. Once the server is started, it will generate a new security configuration, you can then re-run the same command with an additional environment variable -e EMITTER_LICENSE set to the provided value.

docker run -d -p 8080:8080 emitter/server

For the clustered (multi-server) mode, the container can be started using the simple docker run with 3 main parameters.

docker run -d -p 8080:8080 -p 4000:4000 -e EMITTER_LICENSE=[key] -e EMITTER_CLUSTER_SEED=[seed] -e EMITTER_CLUSTER_PASSPHRASE=[name] emitter/server

If you need any help with Emitter Server or any of our client SDKs, please join us at either our gitter chat where most of our team hangs out at or drop us an e-mail at [email protected].

Please submit any Emitter bugs, issues, and feature requests to emitter-io>emitter. If there are any security issues, please email [email protected] instead of posting an open issue in Github.

If you'd like to contribute, please fork the repository and use a feature branch. Pull requests are warmly welcome.

Copyright (c) 2009-2019 Misakai Ltd. This project is licensed under Affero General Public License v3.

Emitter offers support contracts and is now also offered via a commercial license. Please contact [email protected] for more information.