RequestDedup

Coalesces identical concurrent requests into a single network call.

Only GET and HEAD are coalesced by default, and the request body is part of the key — a mismatch there would hand one caller another caller's response.

import { RequestDedup } from 'super-http'

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Usage via HttpClient

client.dedup()                                       // GET + HEAD
client.dedup({ methods: ['GET', 'HEAD', 'POST'] })   // opt in deliberately

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Direct usage

const dedup = new RequestDedup()

const [a, b, c] = await Promise.all([
  dedup.execute('GET:/users/1', () => client.get('/users/1')),
  dedup.execute('GET:/users/1', () => client.get('/users/1')),
  dedup.execute('GET:/users/1', () => client.get('/users/1')),
])
// callCount = 1, a === b === c

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API

execute<T>(key, fn)

execute<T>(key: string, fn: () => Promise<T>): Promise<T>

Executes fn, coalescing concurrent calls with the same key. Once the request settles, the entry is removed — subsequent calls start fresh.

Entries also expire after ttlMs (default 30 s, set via the constructor), so a request that never settles stops pinning its key and dragging every later identical call into the same doomed promise.

size

get size(): number

Number of in-flight deduplicated requests.

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Key format (via HttpClient)

When using .dedup() on HttpClient, the key is computed from the method, the URL, the query params and the request body:

METHOD:url:sha1(params):sha1(body)

A request is not deduplicated at all when:

• its method is outside the eligible set (GET/HEAD by default), or
• its body cannot be compared byte-for-byte — a stream, a FormData, a circular object. Skipping the optimisation costs one extra request; matching wrongly would return the wrong data.

import { buildDedupKey, DEFAULT_DEDUP_METHODS } from 'super-http'

Fixed in 2.0

Before 2.0 the key was METHOD:url:JSON(params) — the body was not part of it. Two concurrent POSTs with different payloads collapsed into one call and the second caller received the first one's response.