Retrying & Backoff Patterns
Retry failing async work a few times with delays; add exponential backoff and tiny jitter; stop after a clear max.
Retrying & Backoff Patterns is a free JavaScript Academy lesson on CoddyKit — lesson 3 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the JavaScript Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why retry?
Goal: Add small, controlled retries.
- Simple retry loop
- Exponential backoff
- Tiny jitter
- Clear max attempts
Delay helper
You need a tiny delay helper to pause between attempts.
// delay: resolve after ms
function delay(ms) {
return new Promise(function (resolve) {
setTimeout(function () { resolve(); }, ms);
});
}
async function demoDelay() {
console.log("wait...");
await delay(5);
console.log("done");
}
demoDelay();
Fake unstable work
This fake task lets us practice retries without real network calls.
// Unstable task: fails first N times, then succeeds
function makeUnstable(failCount, value) {
let left = failCount;
return async function run() {
if (left > 0) {
left = left - 1;
throw new Error("temporary");
}
return value;
};
}
const sometimes = makeUnstable(2, "OK");
sometimes().catch(function (e) { console.log("first:", e.message); });
Fixed retry loop
Fixed interval: wait the same time between attempts; stop after max tries.
// Retry a few times with a fixed wait
async function retryFixed(fn, tries, waitMs) {
let lastError = null;
for (let i = 1; i <= tries; i++) {
try {
return await fn();
} catch (e) {
lastError = e;
console.log("attempt", i, "failed:", e.message);
if (i < tries) {
await delay(waitMs);
}
}
}
throw lastError;
}
(async function () {
const job = makeUnstable(2, "OK");
const result = await retryFixed(job, 3, 5);
console.log("fixed result:", result);
})();
Exponential backoff
Backoff: increase the wait each attempt; add a tiny jitter to avoid spikes.
// Exponential backoff with a tiny jitter
function jitter(ms) {
const wiggle = Math.floor(Math.random() * 3); // 0..2
return ms + wiggle;
}
async function retryBackoff(fn, tries, baseMs) {
let lastError = null;
for (let i = 1; i <= tries; i++) {
try {
return await fn();
} catch (e) {
lastError = e;
console.log("attempt", i, "failed:", e.message);
if (i < tries) {
const wait = jitter(baseMs * Math.pow(2, i - 1));
await delay(wait);
}
}
}
throw lastError;
}
(async function () {
const job = makeUnstable(2, "OK");
const value = await retryBackoff(job, 4, 3);
console.log("backoff result:", value);
})();
Retry tips
Tips:
- Retry only for temporary errors (timeouts, rate limits).
- Do not retry on bad inputs.
- Keep attempts small (3–5) and log failures briefly.
Retry/backoff quiz
Quick check: Backoff basics.
Recap
Recap: You built a fixed retry loop, added exponential backoff with tiny jitter, and set a max attempts to keep apps responsive.
Frequently asked questions
Is the “Retrying & Backoff Patterns” lesson free?
Yes — the full text of “Retrying & Backoff Patterns” is free to read here on the web, and the JavaScript Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the JavaScript Academy course, upgrade to CoddyKit PRO.
What will I learn in “Retrying & Backoff Patterns”?
Retry failing async work a few times with delays; add exponential backoff and tiny jitter; stop after a clear max. You practise JavaScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start JavaScript Academy?
No prior experience is required. JavaScript Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “Retrying & Backoff Patterns” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this JavaScript Academy lesson?
Yes. Every JavaScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Writing async functions; try/catch; parallel vs sequential
- Timeouts & Aborting with AbortController
- Retrying & Backoff Patterns