feat(gateway): add streaming, conditional and range requests (#1989)

This change simplifies code responsible for streaming response
and makes the streaming actually work by telling the payload compression
stream to flush its content on every read().
(previous version was buffering entire thing in Hapi's compressor memory)

We also do content-type detection based on the beginning of the stream
by peeking at first `fileType.minimumBytes` bytes.

- Switched from deprecated `hapi` and `joi` to `@hapi/hapi` and `@hapi/joi`
- Added support for Conditional Requests (RFC7232)
  - Returning `304 Not Modified` if `If-None-Match` is a CID matching `Etag`
  - Added `Last-Modified` to `/ipfs/` responses (improves client-side caching)
  - Always returning `304 Not Modified`
    when `If-Modified-Since` is present for immutable `/ipfs/`
- Added support for Byte Range requests (RFC7233, Section-2.1)
- Added support for `?filename=` parameter (improves downloads of raw cids)

License: MIT
Signed-off-by: Marcin Rataj <lidel@lidel.org>

package.json

@@ -82,6 +82,7 @@
     "stream-to-promise": "^2.2.0"
   },
   "dependencies": {
+    "@hapi/ammo": "^3.1.0",
     "@hapi/hapi": "^18.3.1",
     "@hapi/joi": "^15.0.1",
     "async": "^2.6.1",
@@ -90,6 +91,7 @@
     "bl": "^3.0.0",
     "boom": "^7.2.0",
     "bs58": "^4.0.1",
+    "buffer-peek-stream": "^1.0.1",
     "byteman": "^1.3.5",
     "cid-tool": "~0.2.0",
     "cids": "~0.5.8",

src/http/gateway/resources/gateway.js

@@ -3,13 +3,13 @@
 const debug = require('debug')
 const log = debug('ipfs:http-gateway')
 log.error = debug('ipfs:http-gateway:error')
-const pull = require('pull-stream')
-const pushable = require('pull-pushable')
-const toStream = require('pull-stream-to-stream')
+
 const fileType = require('file-type')
 const mime = require('mime-types')
 const { PassThrough } = require('readable-stream')
 const Boom = require('boom')
+const Ammo = require('@hapi/ammo') // HTTP Range processing utilities
+const peek = require('buffer-peek-stream')
 
 const { resolver } = require('ipfs-http-response')
 const PathUtils = require('../utils/path')
@@ -30,6 +30,20 @@ function detectContentType (ref, chunk) {
   return mime.contentType(mimeType)
 }
 
+// Enable streaming of compressed payload
+// https://github.com/hapijs/hapi/issues/3599
+class ResponseStream extends PassThrough {
+  _read (size) {
+    super._read(size)
+    if (this._compressor) {
+      this._compressor.flush()
+    }
+  }
+  setCompressor (compressor) {
+    this._compressor = compressor
+  }
+}
+
 module.exports = {
   checkCID (request, h) {
     if (!request.params.cid) {
@@ -85,66 +99,114 @@ module.exports = {
       return h.redirect(PathUtils.removeTrailingSlash(ref)).permanent(true)
     }
 
-    return new Promise((resolve, reject) => {
-      let pusher
-      let started = false
+    // Support If-None-Match & Etag (Conditional Requests from RFC7232)
+    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag
+    const etag = `"${data.cid}"`
+    const cachedEtag = request.headers['if-none-match']
+    if (cachedEtag === etag || cachedEtag === `W/${etag}`) {
+      return h.response().code(304) // Not Modified
+    }
 
-      pull(
-        ipfs.catPullStream(data.cid),
-        pull.drain(
-          chunk => {
-            if (!started) {
-              started = true
-              pusher = pushable()
-              const res = h.response(toStream.source(pusher).pipe(new PassThrough()))
+    // Immutable content produces 304 Not Modified for all values of If-Modified-Since
+    if (ref.startsWith('/ipfs/') && request.headers['if-modified-since']) {
+      return h.response().code(304) // Not Modified
+    }
 
-              // Etag maps directly to an identifier for a specific version of a resource
-              res.header('Etag', `"${data.cid}"`)
+    // This necessary to set correct Content-Length and validate Range requests
+    // Note: we need `size` (raw data), not `cumulativeSize` (data + DAGNodes)
+    const { size } = await ipfs.files.stat(`/ipfs/${data.cid}`)
+
+    // Handle Byte Range requests (https://tools.ietf.org/html/rfc7233#section-2.1)
+    const catOptions = {}
+    let rangeResponse = false
+    if (request.headers.range) {
+      // If-Range is respected (when present), but we compare it only against Etag
+      // (Last-Modified date is too weak for IPFS use cases)
+      if (!request.headers['if-range'] || request.headers['if-range'] === etag) {
+        const ranges = Ammo.header(request.headers.range, size)
+        if (!ranges) {
+          const error = Boom.rangeNotSatisfiable()
+          error.output.headers['content-range'] = `bytes */${size}`
+          throw error
+        }
+
+        if (ranges.length === 1) { // Ignore requests for multiple ranges (hard to map to ipfs.cat and not used in practice)
+          rangeResponse = true
+          const range = ranges[0]
+          catOptions.offset = range.from
+          catOptions.length = (range.to - range.from + 1)
+        }
+      }
+    }
 
-              // Set headers specific to the immutable namespace
-              if (ref.startsWith('/ipfs/')) {
-                res.header('Cache-Control', 'public, max-age=29030400, immutable')
-              }
+    const rawStream = ipfs.catReadableStream(data.cid, catOptions)
+    const responseStream = new ResponseStream()
 
-              const contentType = detectContentType(ref, chunk)
+    // Pass-through Content-Type sniffing over initial bytes
+    const { peekedStream, contentType } = await new Promise((resolve, reject) => {
+      const peekBytes = fileType.minimumBytes
+      peek(rawStream, peekBytes, (err, streamHead, peekedStream) => {
+        if (err) {
+          log.error(err)
+          return reject(err)
+        }
+        resolve({ peekedStream, contentType: detectContentType(ref, streamHead) })
+      })
+    })
 
-              log('ref ', ref)
-              log('mime-type ', contentType)
+    peekedStream.pipe(responseStream)
 
-              if (contentType) {
-                log('writing content-type header')
-                res.header('Content-Type', contentType)
-              }
+    const res = h.response(responseStream).code(rangeResponse ? 206 : 200)
 
-              resolve(res)
-            }
-            pusher.push(chunk)
-          },
-          err => {
-            if (err) {
-              log.error(err)
-
-              // We already started flowing, abort the stream
-              if (started) {
-                return pusher.end(err)
-              }
-
-              return reject(err)
-            }
+    // Etag maps directly to an identifier for a specific version of a resource
+    // and enables smart client-side caching thanks to If-None-Match
+    res.header('etag', etag)
 
-            pusher.end()
-          }
-        )
-      )
-    })
+    // Set headers specific to the immutable namespace
+    if (ref.startsWith('/ipfs/')) {
+      res.header('Cache-Control', 'public, max-age=29030400, immutable')
+    }
+
+    log('ref ', ref)
+    log('content-type ', contentType)
+
+    if (contentType) {
+      log('writing content-type header')
+      res.header('Content-Type', contentType)
+    }
+
+    if (rangeResponse) {
+      const from = catOptions.offset
+      const to = catOptions.offset + catOptions.length - 1
+      res.header('Content-Range', `bytes ${from}-${to}/${size}`)
+      res.header('Content-Length', catOptions.length)
+    } else {
+      // Announce support for Range requests
+      res.header('Accept-Ranges', 'bytes')
+      res.header('Content-Length', size)
+    }
+
+    // Support Content-Disposition via ?filename=foo parameter
+    // (useful for browser vendor to download raw CID into custom filename)
+    // Source: https://github.com/ipfs/go-ipfs/blob/v0.4.20/core/corehttp/gateway_handler.go#L232-L236
+    if (request.query.filename) {
+      res.header('Content-Disposition', `inline; filename*=UTF-8''${encodeURIComponent(request.query.filename)}`)
+    }
+
+    return res
   },
 
   afterHandler (request, h) {
     const { response } = request
-    if (response.statusCode === 200) {
+    // Add headers to successfult responses (regular or range)
+    if (response.statusCode === 200 || response.statusCode === 206) {
       const { ref } = request.pre.args
       response.header('X-Ipfs-Path', ref)
       if (ref.startsWith('/ipfs/')) {
+        // "set modtime to a really long time ago, since files are immutable and should stay cached"
+        // Source: https://github.com/ipfs/go-ipfs/blob/v0.4.20/core/corehttp/gateway_handler.go#L228-L229
+        response.header('Last-Modified', 'Thu, 01 Jan 1970 00:00:01 GMT')
+        // Suborigins: https://github.com/ipfs/in-web-browsers/issues/66
         const rootCid = ref.split('/')[2]
         const ipfsOrigin = cidToString(rootCid, { base: 'base32' })
         response.header('Suborigin', 'ipfs000' + ipfsOrigin)

src/http/gateway/routes/gateway.js

@@ -10,6 +10,9 @@ module.exports = {
     pre: [
       { method: resources.gateway.checkCID, assign: 'args' }
     ],
+    response: {
+      ranges: false // disable built-in support, we do it manually
+    },
     ext: {
       onPostHandler: { method: resources.gateway.afterHandler }
     }