stream-static

This is a rewrite of the npm module serve-static and compression for Node v16+. This module offers a composable solution with components offer specific, minimal functionality and limited dependences by emphasizing the Stream APIs provided by Node.js from the filesystem, compression and HTTP.

Why use this instead?

serve-static and compression are difficult to work with if you want to customize their functionality beyond what is provided. This module is written so that it's easy to quickly customize the implementation to suit your needs.

That said, in the author's opinion, nobody should use either serve-static or this module in production because neither are as performant nor as robust as many CDN offerings that serve static content.

Why use serve-static and compression instead?

serve-static and compression support Node before v16.

serve-static provides some features as configuration options that the author of this module felt were "scope creep" or trivial for consumers to implement themselves. For example, serve-static offers a fallthrough option that will replace the 404 response on non existant files with a "fallthrough" to the next handler in the routing middleware. This feature is fairly easy implemented.

For a full comparison of features differences, diff the tests in this module with the tests in serve-static and compression.

Install

$ npm install stream-static

or

$ yarn add stream-static

Dependencies:

> yarn list --prod
yarn list v1.22.15
├─ etag@1.8.1
├─ mime@3.0.0
├─ range-parser@1.2.1
├─ statuses@2.0.1
└─ vary@1.1.2
✨  Done in 0.05s.

API

import { 
  streamStatic,
  normalize_path,
  send,
  basicheaders,
  byterange,
  conditionals,
  compression,
} from 'stream-static'

The provided streamStatic function is a composition itself of the other functions

async function streamStatic(
  root: string, 
  req: IncomingMessage, 
  res: ServerResponse,
  maxage: number = 0,
): Promise<Readable> {
  if (!root) throw new Error('root path required');
  if (req.method === 'POST') {
    throw error(404)
  }
  if (req.method !== 'HEAD' && req.method !== 'GET') {
    res.setHeader('Allow', 'GET, HEAD')
    throw error(405)
  }
  let { path, stat, stream } = await send(root, req.url!);
  try {
    basicheaders(res, path, stat, maxage)
    conditionals(req, res)
  } catch(err) {
    stream.destroy();
    throw err;
  }
  return stream.pipe(byterange(req, res));
}

Or implement your own custom handler serving static files:

async function static_compression(root: string, converter: Transform = null): Promise<void> {
  return async (req, res, next) => {
    if (req.method !== 'GET' && req.method !== 'HEAD') {
      res.statusCode = 405;
      res.setHeader('Allow', 'GET, HEAD')
      res.setHeader('Content-Length', 0)
      res.end();
      return;
    }
    let stream;
    try {
      stream = await streamStatic(resolve(root), req, res);
      if (req.method === 'HEAD') {
        stream.destroy();
        return;
      }
      await pipeline(
        stream,
        byterange(req, res),
        converter ? converter(req, res) : new PassThrough(),
        compression(req, res),
        res,
      );
      res.end();
    } catch (err) {
      console.error(err);
      res.statusCode = isHttpError(err) ? err.statusCode : 500
      if (!res.headersSent) {
        res.setHeader('Content-Length', 0);
      }
      res.end();
      stream?.destroy();
    }
  };
}

Documentation

async function streamStatic(root: string, req: IncomingMessage, res: ServerResponse, maxage: number = 0): Promise

This replicates the functionality of serve-static if you are looking for a replacement (be mindful of some feature differences described above). This function will return a stream of the requested file in root + req.url. If no file exists it will throw a 404. It also supports byte-ranging requests, cache-control, and conditional header requests.

async function normalize_path(root: string, path: string): string

This validate the path through some simple rules and then resolve it to an absolute path.

async function send(root: string, path: string): Promise<{ path: string, stat: Stats, stream: Readable }>

This replicates the send module that serve-static uses to validate the file path and open a file. It will validate the path from the URI (using normalize_path), the file exists and is not a directory before returning a Readable stream.

function basicheaders(res: ServerResponse, path: string, stat: Stats, maxage: number = 0): void

This function will add basic headers to the response based on the file described in stats. This populates headers: Content-Type, Content-Length, Cache-Control, Etag and Last-Modified

function byterange(req: IncomingMessage, res: ServerResponse): Duplex

This function implements the byte range request logic to support Partial Responses based on the Range header, returning a Duplex stream that should be used as a Transform.

function conditionals(req: IncomingMessage, res: ServerResponse): void

This function implements the handling of conditional headers: if-match, if-none-match, if-unmodified-since, and if-modified-since. This includes support for etags.

function compression(req: IncomingMessage, res: ServerResponse, threshhold: number = 1024): Transform

This is the replacement for compression. It will respect the requested encoding and return a Transform stream (or PassThrough) to either do the compression or not based on what the client requested.

License

MIT