Skip to content

perf: increase undici HTTP/2 pool from 4x64 to 20x128 streams #801

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
tode-rl merged 1 commit into from
Jun 15, 2026
Merged

perf: increase undici HTTP/2 pool from 4x64 to 20x128 streams #801

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 6 additions & 4 deletions src/lib/undici-fetch.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -37,10 +37,12 @@ import { MultipartBody } from '../_shims/MultipartBody';
import { type Fetch } from '../core';

const KEEP_ALIVE_TIMEOUT_MS = 10 * 60 * 1000;
// Bound the pool to a few TLS sessions per origin and multiplex many H2 streams
// over each. 4 x 64 = 256 concurrent requests in flight before undici queues the rest.
const H2_MAX_CONNECTIONS = 4;
const H2_MAX_CONCURRENT_STREAMS = 64;
// Bound the pool to several TLS sessions per origin and multiplex H2 streams over
// each. The server typically advertises MAX_CONCURRENT_STREAMS=100-128; we use 128
// per connection to match. 20 x 128 = 2560 concurrent requests in flight before
// undici queues the rest.
const H2_MAX_CONNECTIONS = 20;
const H2_MAX_CONCURRENT_STREAMS = 128;

// One module-scoped default dispatcher, reused across requests: a bounded HTTP/2 pool
// with keep-alive. `allowH2` negotiates h2 over TLS via ALPN and transparently falls
Expand Down