Exponential backoff spaces retry attempts by increasing the delay after each failure, commonly doubling it: 1, 2, 4, 8, 16, and 32 seconds. It gives an API time to recover when the client cannot observe the server’s internal state. section 29.2.1
Use it for transient or time-related failures, not automatically for permanent failures. A request returning HTTP 429 may be retriable, while HTTP 403 is generally unsafe to retry. section 29.6
A practical retry policy should:
- Bound the retry count and maximum delay so a request eventually fails instead of waiting indefinitely. section 29.3.2
- Add random jitter to each delay so many clients do not retry simultaneously and overload the service again. section 29.3.2
- Honor server-provided timing when available; a Retry-After value overrides the client’s normal backoff delay. section 29.2.2 section 29.3.4
- Treat the policy as client-enforced: the server can recommend retry behavior but cannot control whether clients follow it. section 29.4
Retrying a chat-room lookup
A getChatRoomWithRetries function can begin with a one-second delay, double the backoff after each failed request, stop after a configured retry count, cap the delay at 32 seconds, and add up to one second of jitter. The final policy first uses Retry-After when the response supplies it; otherwise it uses jittered exponential backoff. section 29.3.2 section 29.3.4
Listing 29.5 Final API definition
async function getChatRoomWithRetries(
id: string, maxDelayMs = 32000, 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) {
actualDelayMs = Number(
e.response.headers['Retry-After']) * 1000;
} else {
actualDelayMs = delayMs + (Math.random() * 1000);
}
return setTimeout(resolve, actualDelayMs);
});
delayMs *= 2;
if (delayMs > maxDelayMs) delayMs = maxDelayMs;
}
}
});
}
Inspect a complete TypeScript-style retrieval function combining retry limits, delay caps, jitter, and server-directed timing. section 29.3.4
