Add WS filtering using WS pool strategy

[ishantiw]

Description

Add WS filtering using WS pool strategy. The idea is to support topic based communication over ws channel.

To achieve this, we need ws clients pooling mechanism where ws clients send subscribe message with the list of topics (ws.send({ type: 'subscribe', topic: 'app' })) and then the ws server adds these client sockets to corresponding topics as per the subscribe message sent by the client. Below is an idea for this strategy.

// At client
wsClientChannel.connect();
wsClientChannel.on('app', handler()); wsClientChannel.on('app:getNodeStatus', handler()); // will call ws.send({ type: 'subscribe', topics: ['app',’block']})


// Bus
const topicPool = {
   // all registered topics
  'app': [clientSocket1, clientSocket2],
  'dpos': [clientSocket2, clientSocket5],
}

wsServer.on('connection', sock => {
  // Broker registers the new client along with the topics subscribed and uses it to send 

  wsServer.on('message', msg => {
    if(message.type === 'subscribe') {
      for (const topic of msg.topics) {
         // subscribes the event for that client in broker
         topicPool[topic].push(sock);
      }
   }
  })
});

publish(event, data) {
  // iterate through peer Pool for the given event and send to clients
  const topic = event.split(':')[0];
  for (const client of topicPool[topic]) {
    client.send(data);
  }
}

Acceptance Criteria

• Unit tests under test/unit/controller/ws should pass
• Add additional functional/integration/unit tests to verify topic based ws API communication

Additional Information

• Related Improve plugin and channel implementation #6612
• Refer to design document for more details