micro-ftch

Wrappers for built-in fetch() enabling killswitch, logging, concurrency limit and other features.

fetch is great, however, its usage in secure environments is complicated. The library makes it simple.

Usage

A standalone file micro-ftch.js is also available.

npm install micro-ftch

1import { ftch, jsonrpc, replayable } from 'micro-ftch';
2
3let enabled = false;
4const net = ftch(fetch, {
5  killswitch: () => enabled,
6  log: (url, options) => console.log(url, options),
7  timeout: 5000,
8  concurrencyLimit: 10,
9});
10const res = await net('https://example.com');
11
12// Composable
13const rpc = jsonrpc(net, 'http://rpc_node/', {
14  headers: {},
15  batchSize: 20,
16});
17const res1 = await rpc.call('method', 'arg0', 'arg1');
18const res2 = await rpc.callNamed('method', { arg0: '0', arg1: '1' }); // named arguments
19const testRpc = replayable(rpc);
20// Basic auth auto-parsing
21await net('https://user:pwd@httpbin.org/basic-auth/user/pwd');

• ftch
  • killswitch
  • log
  • timeout
  • concurrencyLimit
  • Basic auth
• jsonrpc
• replayable
• Privacy
• License

There are three wrappers over fetch():

1. ftch(fetch) - killswitch, logging, timeouts, concurrency limits, basic auth
2. jsonrpc(fetch) - batched JSON-RPC functionality
3. replayable(fetch) - log & replay network requests without actually calling network code.

ftch

Basic wrapper over fetch().

killswitch

When kill-switch is enabled, all requests will throw an error. You can dynamically enable and disable it any any time.

1let ENABLED = true;
2const f = ftch(fetch, { killswitch: () => ENABLED });
3f('http://localhost'); // ok
4ENABLED = false;
5f('http://localhost'); // throws
6ENABLED = true;
7f('http://localhost'); // ok

log

1const f = ftch(fetch, { log: (url, opts) => console.log('fetching', url, opts) });
2f('http://url/'); // will print request information

timeout

1// browser and OS may have additional timeouts, we cannot override them
2// a: per-request timeout
3const f = ftch(fetch);
4const res = await f('http://url/', { timeout: 1000 }); // throws if request takes more than one second
5
6// b: timeout for all
7const f = ftch(fetch, { timeout: 1000 });
8const res = await f('http://url/'); // throws if request takes more than one second

concurrencyLimit

Allows to not accidentally hit rate limits or do DoS.

1// browser and OS may have additional limits, we cannot override them
2const f = ftch(fetch, { concurrencyLimit: 1 });
3const res = await Promise.all([f('http://url1/'), f('http://url2/')]); // these would be processed sequentially

Basic auth

1const f = ftch(fetch);
2const res = await f('https://user:pwd@httpbin.org/basic-auth/user/pwd'); // supports basic auth!

jsonrpc

Supports batching multiple HTTP requests into one "Batched" JSON RPC HTTP request. Can massively speed-up when servers are single-threaded, has small per-user limits

1const rpc = jsonrpc(fetch, 'http://rpc_node/', {
2  headers: {},
3  batchSize: 20,
4});
5const res = await rpc.call('method', 'arg0', 'arg1');
6const res2 = await rpc.callNamed('method', { arg0: '0', arg1: '1' }); // named arguments

replayable

Small utility to log & replay network requests in tests, without actually calling network code.

1const ftch = ftch(fetch);
2const replayCapture = replayable(ftch); // wraps fetch
3await replayCapture('http://url/1'); // real network
4await replayCapture('http://url/2');
5const logs = replayCapture.export(); // Exports logs
6
7// When logs provided - use cached version (faster)
8const replayTest = replayable(ftch, JSON.parse(logs));
9await replayTest('http://url/1'); // cached
10await replayTest('http://url/2'); // cached
11await replayTest('http://url/3'); // real network
12
13// When done and everything is captured, turn on 'offline' mode to throw on network requests:
14const replayTestOffline = replayable(ftch, JSON.parse(logs), {
15  offline: true,
16});
17await replayTest('http://url/1'); // cached
18await replayTest('http://url/2'); // cached
19await replayTest('http://url/3'); // throws!

Privacy

ftch() disables referrer by default by setting referrerPolicy: 'no-referrer'.

License

MIT (c) Paul Miller (https://paulmillr.com), see LICENSE file.