request deduplication

request-deduplication

function UpdateChatRoom(req: UpdateChatRoomRequest): ChatRoom { 
  if (req.requestId === undefined) { // #A
    return ChatRoom.update(...);
  }
  const hash = crypto.createHash('sha256').update(JSON.stringify(req)).digest('hex');
  const cachedResponse = cache.get(req.requestId); 
  if (!cachedResult) { // #B
    const response = ChatRoom.update(...); 
    cache.set(req.requestId, { response, hash }); // #C 
    return response;
  }
  if (hash == cachedResult.hash) { // #D 
    return cachedResult.response;
  } else {
    throw new Error('409 Conflict'); // #E
  } 
}