Request Deduplication

When multiple parts of your application fetch the same URL simultaneously, fetch-smartly can ensure only one actual network request is made.

How It Works

The DedupManager tracks in-flight requests by a key (METHOD:URL). If a second request arrives with the same key while the first is still pending, both callers share the same promise. Once the request settles, the entry is automatically cleaned up.

Only safe (idempotent) methods are eligible: GET, HEAD, OPTIONS. Mutation methods (POST, PUT, PATCH, DELETE) are never deduplicated.

Usage

import { DedupManager, getDedupKey, isDedupEligible, fetchWithRetry } from 'fetch-smartly';

const dedup = new DedupManager();

async function smartFetch(url: string, method = 'GET') {
  if (!isDedupEligible(method)) {
    return fetchWithRetry({ url, method });
  }

  const key = getDedupKey(method, url);
  const existing = dedup.get(key);
  if (existing) return existing;

  return dedup.track(key, fetchWithRetry({ url, method }));
}

// Both resolve with the same response from a single fetch:
const [a, b] = await Promise.all([
  smartFetch('https://api.example.com/users'),
  smartFetch('https://api.example.com/users'),
]);
// a === b → true

API

Method	Description
dedup.has(key)	Check if a request is in flight
dedup.get(key)	Get the in-flight promise
dedup.track(key, promise)	Register and auto-cleanup a request
dedup.size	Number of in-flight requests
dedup.clear()	Remove all tracked entries
getDedupKey(method, url)	Generate a dedup key
isDedupEligible(method)	Check if method is safe for dedup