Queue requests from createRemoteFileNode and control concurrency of r…

…equests (gatsbyjs#4616)

* Chunk the requests to download media objects from WP.
The blog I work on has over 9,000 media objects and currently, it tries
to download them all. This PR chunks them in groups of 100, but that
setting can be increased.

* Remove prettier forrmatting from the readme

* Clean up and document create-remote-file-node
Add Better Queue for more control over processing

* Rollback changes to wp source files

* Add queue for requesting wp objects
update readme with new config option

* Revert files to master

* No longer throw an exception when an error occurs. Just resolve with
null and move on

* Remove file lock lookup for now. 200 concurrent requests is a safe
number and we can look to change this in the future

* Cosmoetic updates

* Remove console.log

src/create-remote-file-node.js

@@ -3,112 +3,275 @@ const got = require(`got`)
 const crypto = require(`crypto`)
 const path = require(`path`)
 const { isWebUri } = require(`valid-url`)
+const Queue = require(`better-queue`)
 
 const { createFileNode } = require(`./create-file-node`)
 const cacheId = url => `create-remote-file-node-${url}`
 
+/********************
+ * Type Definitions *
+ ********************/
+
 /**
- * Index of promises resolving to File node from remote url
+ * @typedef {Redux}
+ * @see [Redux Docs]{@link https://redux.js.org/api-reference}
  */
-const processingCache = {}
 
-module.exports = ({ url, store, cache, createNode, auth = {} }) => {
-  // Check if we already requested node for this remote file
-  // and return stored promise if we did.
-  if (processingCache[url]) {
-    return processingCache[url]
+/**
+ * @typedef {GatsbyCache}
+ * @see gatsby/packages/gatsby/utils/cache.js
+ */
+
+/**
+ * @typedef {Auth}
+ * @type {Object}
+ * @property {String} htaccess_pass
+ * @property {String} htaccess_user
+ */
+
+/**
+ * @typedef {CreateRemoteFileNodePayload}
+ * @typedef {Object}
+ * @description Create Remote File Node Payload
+ *
+ * @param  {String} options.url
+ * @param  {Redux} options.store
+ * @param  {GatsbyCache} options.cache
+ * @param  {Function} options.createNode
+ * @param  {Auth} [options.auth]
+ */
+
+/*********
+ * utils *
+ *********/
+
+/**
+ * createHash
+ * --
+ *
+ * Create an md5 hash of the given str
+ * @param  {Stringq} str
+ * @return {String}
+ */
+const createHash = (str) => crypto
+  .createHash(`md5`)
+  .update(str)
+  .digest(`hex`)
+
+const CACHE_DIR = `.cache`
+const FS_PLUGIN_DIR = `gatsby-source-filesystem`
+
+/**
+ * createFilePath
+ * --
+ *
+ * @param  {String} directory
+ * @param  {String} filename
+ * @param  {String} url
+ * @return {String}
+ */
+const createFilePath = (directory, filename, ext) => path.join(
+  directory,
+  CACHE_DIR,
+  FS_PLUGIN_DIR,
+  `${filename}${ext}`
+)
+
+/********************
+ * Queue Management *
+ ********************/
+
+/**
+ * Queue
+ * Use the task's url as the id
+ * When pushing a task with a similar id, prefer the original task
+ * as it's already in the processing cache
+ */
+const queue = new Queue(pushToQueue, {
+  id: `url`,
+  merge: (old, _, cb) => cb(old),
+  concurrent: 200,
+})
+
+/**
+ * @callback {Queue~queueCallback}
+ * @param {*} error
+ * @param {*} result
+ */
+
+/**
+ * pushToQueue
+ * --
+ * Handle tasks that are pushed in to the Queue
+ *
+ *
+ * @param  {CreateRemoteFileNodePayload}          task
+ * @param  {Queue~queueCallback}  cb
+ * @return {Promise<null>}
+ */
+async function pushToQueue (task, cb) {
+  try {
+    const node = await processRemoteNode(task)
+    return cb(null, node)
+  } catch (e) {
+    return cb(null, e)
   }
+}
 
-  return (processingCache[url] = new Promise(async (resolve, reject) => {
-    if (!url || isWebUri(url) === undefined) {
-      resolve()
-      return
-    }
+/******************
+ * Core Functions *
+ ******************/
+
+/**
+ * requestRemoteNode
+ * --
+ * Download the requested file
+ *
+ * @param  {String}   url
+ * @param  {Headers}  headers
+ * @param  {String}   tmpFilename
+ * @param  {String}   filename
+ * @return {Promise<Object>}  Resolves with the [http Result Object]{@link https://nodejs.org/api/http.html#http_class_http_serverresponse}
+ */
+const requestRemoteNode = (url, headers, tmpFilename, filename) => new Promise((resolve, reject) => {
+  const responseStream = got.stream(url, { ...headers, timeout: 30000 })
+  responseStream.pipe(fs.createWriteStream(tmpFilename))
+  responseStream.on(`downloadProgress`, pro => console.log(pro))
+
+  // If there's a 400/500 response or other error.
+  responseStream.on(`error`, (error, body, response) => {
+    fs.removeSync(tmpFilename)
+    reject({ error, body, response })
+  })
 
-    // Ensure our cache directory exists.
-    await fs.ensureDir(
-      path.join(
-        store.getState().program.directory,
-        `.cache`,
-        `gatsby-source-filesystem`
-      )
+  responseStream.on(`response`, response => {
+    resolve(response)
+  })
+})
+
+/**
+ * processRemoteNode
+ * --
+ * Request the remote file and return the fileNode
+ *
+ * @param {CreateRemoteFileNodePayload} options
+ * @return {Promise<Object>} Resolves with the fileNode
+ */
+async function processRemoteNode ({ url, store, cache, createNode, auth = {} }) {
+  // Ensure our cache directory exists.
+  const programDir = store.getState().program.directory
+  await fs.ensureDir(
+    path.join(
+      programDir,
+      CACHE_DIR,
+      FS_PLUGIN_DIR
     )
+  )
 
-    // See if there's response headers for this url
-    // from a previous request.
-    const cachedHeaders = await cache.get(cacheId(url))
-    const headers = {}
+  // See if there's response headers for this url
+  // from a previous request.
+  const cachedHeaders = await cache.get(cacheId(url))
+  const headers = {}
 
-    // Add htaccess authentication if passed in. This isn't particularly
-    // extensible. We should define a proper API that we validate.
-    if (auth && auth.htaccess_pass && auth.htaccess_user) {
-      headers.auth = `${auth.htaccess_user}:${auth.htaccess_pass}`
-    }
+  // Add htaccess authentication if passed in. This isn't particularly
+  // extensible. We should define a proper API that we validate.
+  if (auth && auth.htaccess_pass && auth.htaccess_user) {
+    headers.auth = `${auth.htaccess_user}:${auth.htaccess_pass}`
+  }
 
-    if (cachedHeaders && cachedHeaders.etag) {
-      headers[`If-None-Match`] = cachedHeaders.etag
-    }
+  if (cachedHeaders && cachedHeaders.etag) {
+    headers[`If-None-Match`] = cachedHeaders.etag
+  }
 
-    // Create the temp and permanent file names for the url.
-    const digest = crypto
-      .createHash(`md5`)
-      .update(url)
-      .digest(`hex`)
-    const tmpFilename = path.join(
-      store.getState().program.directory,
-      `.cache`,
-      `gatsby-source-filesystem`,
-      `tmp-` + digest + path.parse(url).ext
-    )
-    const filename = path.join(
-      store.getState().program.directory,
-      `.cache`,
-      `gatsby-source-filesystem`,
-      digest + path.parse(url).ext
-    )
+  // Create the temp and permanent file names for the url.
+  const digest = createHash(url)
+  const ext = path.parse(url).ext
 
-    // Fetch the file.
-    let statusCode
-    let responseHeaders
-    let responseError = false
-    const responseStream = got.stream(url, headers)
-    responseStream.pipe(fs.createWriteStream(tmpFilename))
-    responseStream.on(`downloadProgress`, pro => console.log(pro))
-
-    // If there's a 400/500 response or other error.
-    responseStream.on(`error`, (error, body, response) => {
-      responseError = true
-      fs.removeSync(tmpFilename)
-      reject(error, body, response)
-    })
+  const tmpFilename = createFilePath(programDir, `tmp-${digest}`, ext)
+  const filename = createFilePath(programDir, digest, ext)
+
+  // Fetch the file.
+  try {
+    const response = await requestRemoteNode(url, headers, tmpFilename, filename)
+    // Save the response headers for future requests.
+    cache.set(cacheId(url), response.headers)
 
     // If the status code is 200, move the piped temp file to the real name.
+    if (response.statusCode === 200) {
+      await fs.move(tmpFilename, filename, { overwrite: true })
     // Else if 304, remove the empty response.
-    responseStream.on(`response`, response => {
-      statusCode = response.statusCode
-      responseHeaders = response.headers
-    })
+    } else {
+      await fs.remove(tmpFilename)
+    }
+
+    // Create the file node.
+    const fileNode = await createFileNode(filename, {})
+
+    // Override the default plugin as gatsby-source-filesystem needs to
+    // be the owner of File nodes or there'll be conflicts if any other
+    // File nodes are created through normal usages of
+    // gatsby-source-filesystem.
+    createNode(fileNode, { name: `gatsby-source-filesystem` })
 
-    responseStream.on(`end`, response => {
-      if (responseError) return
-
-      // Save the response headers for future requests.
-      cache.set(cacheId(url), responseHeaders)
-      if (statusCode === 200) {
-        fs.moveSync(tmpFilename, filename, { overwrite: true })
-      } else {
-        fs.removeSync(tmpFilename)
-      }
-
-      // Create the file node and return.
-      createFileNode(filename, {}).then(fileNode => {
-        // Override the default plugin as gatsby-source-filesystem needs to
-        // be the owner of File nodes or there'll be conflicts if any other
-        // File nodes are created through normal usages of
-        // gatsby-source-filesystem.
-        createNode(fileNode, { name: `gatsby-source-filesystem` })
-        resolve(fileNode)
-      })
+    return fileNode
+  } catch (err) {
+    // ignore
+  }
+  return null
+}
+
+/**
+ * Index of promises resolving to File node from remote url
+ */
+const processingCache = {}
+/**
+ * pushTask
+ * --
+ * pushes a task in to the Queue and the processing cache
+ *
+ * Promisfy a task in queue
+ * @param {CreateRemoteFileNodePayload} task
+ * @return {Promise<Object>}
+ */
+const pushTask = (task) => new Promise((resolve, reject) => {
+  queue
+    .push(task)
+    .on(`finish`, (task) => {
+      resolve(task)
+    })
+    .on(`failed`, () => {
+      resolve()
     })
-  }))
+})
+
+/***************
+ * Entry Point *
+ ***************/
+
+/**
+ * createRemoteFileNode
+ * --
+ *
+ * Download a remote file
+ * First checks cache to ensure duplicate requests aren't processed
+ * Then pushes to a queue
+ *
+ * @param {CreateRemoteFileNodePayload} options
+ * @return {Promise<Object>}                  Returns the created node
+ */
+module.exports = ({ url, store, cache, createNode, auth = {} }) => {
+  // Check if we already requested node for this remote file
+  // and return stored promise if we did.
+  if (processingCache[url]) {
+    return processingCache[url]
+  }
+
+
+  if (!url || isWebUri(url) === undefined) {
+    // should we resolve here, or reject?
+    // Technically, it's invalid input
+    return Promise.resolve()
+  }
+
+  return (processingCache[url] = pushTask({ url, store, cache, createNode, auth }))
 }