Updated Readme

Added internal message API descriptions

readme.md

@@ -61,6 +61,30 @@ The DM is divided into two submodules the **Dispatcher** and the **Dispatch Daem
 - For Worker nodes modify the config.json in dispatch_daemon to provide an unique ID to each node.
 - Run the Master and Worker server as `npm start` or `node index.js`
 
+### Internal Communication Interfaces
+Internally DM uses Apache Kafka for interaction between the Dispatcher and the Dispatch Agents, while the messages are in JSON format. 
+Every Dispatch Agent listens on a topic which is its own UID (Currently the primary IP Address), the Dispatcher listens on the topics *"response"* and *"heartbeat"*.
+- **Request Message:** When a request is received at the Dispatcher, it directs the Dispatch Agent to start a worker environment. A message is sent via the chose Worker's ID topic. \
+Format:
+```javascript
+{ type: "execute",
+  function_id: "onetime unique ID",
+  runtime: "isolation runtime",
+  functionHash: "hash of the function to be run" }
+```
+- **Response Message:** In response, the worker executes the function, pulling resources from the central repository as required and sends a response. \
+Format:
+```javascript
+{ status: 'success',
+  result: 'result of the execution',
+  function_id: 'onetime unique ID' }
+```
+- **Heartbeat Message:** The Dispatch Daemons also publish a periodic Heartbeat message back to the Dispatcher as a liveness test.\
+Format:
+```javascript
+{ address: 'UID of the worker' }
+```
+
 ### Interaction API
 
 The platform works via a HTTP API based interface, the interface is divided into two parts: