exponential back-off algorithm

retries-exp-back-off

async function getChatRoomWithRetries(id: string, maxDelayMs = 32, maxRetries = 10): Promise<ChatRoom> {
  return new Promise<ChatRoom>(async (resolve, reject) => {
    let retryCount = 0;
    let delayMs = 1000;
    while (true) {
      try {
        return resolve(GetChatRoom({ id }));
      } catch (e) {
        if (retryCount++ > maxRetries) return reject(e);
        await new Promise((resolve) => {
          let actualDelayMs;
          if ('Retry-After' in e.response.headers) { // #A
            actualDelayMs = Number(e.response.headers['Retry-After']) * 1000;
          } else {
            actualDelayMs = delayMs + (Math.random() * 1000); // #B 
           }
          return setTimeout(resolve, actualDelay);
        });
        delayMs *= 2;
        if (delayMs > maxDelayMs) delayMs = maxDelayMs;
      }
} });
}