• Description
• Main Components
  • Message Broker
  • Consumer
  • Producer
  • RTP-Server
• Quality of Service (QoS)
• User Technologies

Unbelievable Message Broker written using Scala Language + Akka Library.

It can receive TCP connections from both Producers and Consumers. Producers sends data, which mandatory contains topic for every message, and then all the messages will be split by the Topic criteria. Consumers receives list of topics, and chooses which topic it wants to be subscribed to. Afterwards, it successfully will start receiving corresponding messages.

Quantity of Consumers and Producers may vary and are limited only by Akka TCP possibilities. Consumers and Producers can be developed as you wish and using language you wish, the only point it has to create TCP connection and follow several rules that are mentioned below.

Note: You can dockerize all three projects, just by firstly running runDocker.sh in every project. Pulling docker image of mongodb (docker pull mongo) and rtp server (mentionet below) and then running runCompose.sh you can compose and run all the images together and then run whole project with one producer and one consumer.

All the diagrams and documents are located in folder docs.

For all the Apps, you can find configuration in /src/resources/application.conf. There you can configure network addresses for Apps (like hostname, messagebroker and address of mongodb server. For every value default is localhost).

Another Note: If you are not similar to Scala, make sure that you have installed needed tools for that. If you are using IntelliJ check this link.

• Message Broker

The main component, which is described above.

Located in the folder messageBroker.

• Consumer

Recommended small app also developer using Scala Language + Akka Library. Connects to the Message Broker, subscribes and receives messages from it and prints them. Pretty easy, huh?

Located in the folder consumer.

Of course, you can create your own Consumer. How it can connect to the Message Broker:

{
  "connectionType": "Consumer",
  "QoS": 0
}

Note: QoS stands for "Quality of Service" like MQTT does have, which can receive values from 0 to 2. More about QoS you can read here.

Note: If Consumer will include topic that do not exist in Message Broker actual list, it this topic will be ignored.

To send selected topics back, just send the next JSON:

{
  "topics" : 
  [
    "en",
    "es"
  ]
}

Instead of "en", "es" put your own list of topics.

object MessagesHandler {

  case class Acknowledgement(id: Int)

}

• Producer

Recommended app developed using (guess what?) Scala Language + Akka Library. Connects to the Message Broker and to the Docker Image rtp-server, which is described below.

Located in the folder producer.

Of course, you can create your own Producer. How it can connect to the Message Broker:

{
  "connectionType": "Producer",
  "QoS": 0
}

{
  "id": 12,
  "topic": "en",
  "message": "this is a message"
}

• RTP-server

The Docker Image courtesy provided by our beloved FAFer Alex Burlacu. Actually is a server providing SSE Stream with Tweeter tweets in JSON format. It can be pulled by using command:

docker pull alexburlacu/rtp-server:faf18x

To run the Docker Image, you can use next line:

docker run -p 4000:4000 alexburlacu/rtp-server:faf18x

Similar to MQTT, this Message Broker has QoS Technology.

For this QoS Level consumer don't have to make any kind of Acknowledgement. Just receive it and that's all.

For this QoS Level Receiver just has to send back Acknowledgement message with id of the received message and ackType, with value ack. If Message Broker is a Sender and has not received Acknowledgement message, it resends original message every 100 milliseconds. If there were last 100 message resends without Acknowledgement, the connection will be closed by the Message Broker.

For this QoS Level Sender sends original message to the Receiver, and waits for the Acknowledgement message from the Sender with corresponding id and ackType with value recAck. If such Acknowledgement was not received, Sernder resends original message. If Sender has received Acknowledgement from Receiver, it stops resending original message and sends to the Receiver another Acknowledgement message with the same id and ackType with value senAck. When Receiver gets such message, it processes the original message, and sends to Sender Acknowledgement message with (guess what?) same id and ackType with value done. Afterwards, Sender can easily resend this message again.

• Scala Language - 2.13.0

• Akka Library - 2.6.18

• Alpakka SSE - 3.0.4

• Akka Persistance - 2.6.18

• Akka Persistance Mongo Scala - 3.0.8

• Json4s Jackson - 4.1.0M1