gatsby-source-filesystem-with-queue

A Gatsby source plugin for sourcing data into your Gatsby application
from your local filesystem.

The plugin creates File nodes from files. The various "transformer"
plugins can transform File nodes into various other types of data e.g.
gatsby-transformer-json transforms JSON files into JSON data nodes and
gatsby-transformer-remark transforms markdown files into MarkdownRemark
nodes from which you can query an HTML representation of the markdown.

The only difference between this and gatsby-source-filesystem is that
this plugin processes files in an asynchronous queue, with a configurable
limit on how many files can be processed simultaneously. This limit is
800 by default, which should be fine on most systems, but you can lower
it with the GATSBY_CONCURRENT_FILES environment variable if you still
encounter errors (or raise it to speed things up).

By processing files in a queue, we can avoid EMFILE: TOO MANY OPEN FILES
errors which occur on large sites on certain systems.

Install

npm install gatsby-source-filesystem-with-queue

How to use

``javascript
// In your gatsby-config.js
module.exports = {
plugins: [
// You can have multiple instances of this plugin
// to read source nodes from different locations on your
// filesystem.
//
// The following sets up the Jekyll pattern of having a
// "pages" directory for Markdown files and a "data" directory
// for .json, .yaml, .csv.
{
resolve: gatsby-source-filesystem-with-queue,
options: {
name: pages,
path: ${__dirname}/src/pages/,
},
},
{
resolve: gatsby-source-filesystem-with-queue,
options: {
name: data,
path: ${__dirname}/src/data/,
ignore: [*/\.], // ignore files starting with a dot
},
},
],
}
`

Options

In addition to the name and path parameters you may pass an optional ignore array of file globs to ignore.

They will be added to the following default list:

`text
*/.un~
**/.DS_Store
**/.gitignore
**/.npmignore
**/.babelrc
**/yarn.lock
**/node_modules
..//dist/
`

To prevent concurrent requests overload of processRemoteNode, you can adjust the 200 default concurrent downloads, with GATSBY_CONCURRENT_DOWNLOAD environment variable.

To prevent opening too many files, you can adjust the 8000 default concurrent files open, with GATSBY_CONCURRENT_FILES environment variable.

How to query

You can query file nodes like the following:

`graphql
{
allFile {
edges {
node {
extension
dir
modifiedTime
}
}
}
}
`

To filter by the name you specified in the config, use sourceInstanceName:

`graphql
{
allFile(filter: { sourceInstanceName: { eq: "data" } }) {
edges {
node {
extension
dir
modifiedTime
}
}
}
}
`

Helper functions

gatsby-source-filesystem-with-queue exports three helper functions:

- createFilePath
- createRemoteFileNode
- createFileNodeFromBuffer

$3

When building pages from files, you often want to create a URL from a file's path on the file system. E.g. if you have a markdown file at src/content/2018-01-23-an-exploration-of-the-nature-of-reality/index.md, you might want to turn that into a page on your site at example.com/2018-01-23-an-exploration-of-the-nature-of-reality/. createFilePath is a helper function to make this task easier.

`javascript
createFilePath({
// The node you'd like to convert to a path
// e.g. from a markdown, JSON, YAML file, etc
node,
// Method used to get a node
// The parameter from onCreateNode should be passed in here
getNode,
// The base path for your files.
// It is relative to the options.path setting in the gatsby-source-filesystem-with-queue entries of your gatsby-config.js.
// Defaults to src/pages. For the example above, you'd use src/content.
basePath,
// Whether you want your file paths to contain a trailing / slash
// Defaults to true
trailingSlash,
})
`

#### Example usage

`javascript
const { createFilePath } = require(gatsby-source-filesystem-with-queue)

exports.onCreateNode = ({ node, getNode, actions }) => {
const { createNodeField } = actions
// Ensures we are processing only markdown files
if (node.internal.type === "MarkdownRemark") {
// Use createFilePath to turn markdown files in our data/faqs directory into /faqs/slug
const relativeFilePath = createFilePath({
node,
getNode,
basePath: "data/faqs/",
})

// Creates new query'able field with name of 'slug'
createNodeField({
node,
name: "slug",
value: /faqs${relativeFilePath},
})
}
}
`

$3

When building source plugins for remote data sources such as headless CMSs, their data will often link to files stored remotely that are often convenient to download so you can work with them locally.

The createRemoteFileNode helper makes it easy to download remote files and add them to your site's GraphQL schema.

While downloading the assets, special characters (regex: /:|\/|\|\?|"|<|>|\||\\/g) in filenames are replaced with a hyphen "-". When special characters are found a file hash is added to keep files unique e.g a:file.jpg becomes a-file-73hd.jpg (as otherwise a:file.jpg and afile.jpg would overwrite themselves).

`javascript
createRemoteFileNode({
// The source url of the remote file
url: https://example.com/a-file.jpg,

// The id of the parent node (i.e. the node to which the new remote File node will be linked to.
parentNodeId,

// Gatsby's cache which the helper uses to check if the file has been downloaded already. It's passed to all Node APIs.
getCache,

// The action used to create nodes
createNode,

// A helper function for creating node Ids
createNodeId,

// OPTIONAL
// Adds htaccess authentication to the download request if passed in.
auth: { htaccess_user: USER, htaccess_pass: PASSWORD },

// OPTIONAL
// Adds extra http headers to download request if passed in.
httpHeaders: { Authorization: Bearer someAccessToken },

// OPTIONAL
// Sets the file extension
ext: ".jpg",
})
`

#### Example usage

The following example is pulled from gatsby-source-wordpress. Downloaded files are created as File nodes and then linked to the WordPress Media node, so it can be queried both as a regular File node and from the localFile field in the Media node.

`javascript
const { createRemoteFileNode } = require(gatsby-source-filesystem-with-queue)

exports.downloadMediaFiles = ({
nodes,
getCache,
createNode,
createNodeId,
_auth,
}) => {
nodes.map(async node => {
let fileNode
// Ensures we are only processing Media Files
// wordpress__wp_media is the media file type name for WordPress
if (node.__type === wordpress__wp_media) {
try {
fileNode = await createRemoteFileNode({
url: node.source_url,
parentNodeId: node.id,
getCache,
createNode,
createNodeId,
auth: _auth,
})
} catch (e) {
// Ignore
}
}

// Adds a field localFile to the node
// ___NODE appendix tells Gatsby that this field will link to another node
if (fileNode) {
node.localFile___NODE = fileNode.id
}
})
}
`

The file node can then be queried using GraphQL. See an example of this in the gatsby-source-wordpress README where downloaded images are queried using gatsby-transformer-sharp to use in the component gatsby-image.

#### Retrieving the remote file name and extension

The helper tries first to retrieve the file name and extension by parsing the url and the path provided (e.g. if the url is https://example.com/image.jpg, the extension will be inferred as .jpg and the name as image). If the url does not contain an extension, we use the file-type package to infer the file type. Finally, the name and the extension _can_ be explicitly passed, like so:

`javascript
createRemoteFileNode({
// The source url of the remote file
url: https://example.com/a-file-without-an-extension,
parentNodeId: node.id,
getCache,
createNode,
createNodeId,
// if necessary!
ext: ".jpg",
name: "image",
})
`

$3

When working with data that isn't already stored in a file, such as when querying binary/blob fields from a database, it's helpful to cache that data to the filesystem in order to use it with other transformers that accept files as input.

The createFileNodeFromBuffer helper accepts a Buffer, caches its contents to disk, and creates a file node that points to it.

The name of the file can be passed to the createFileNodeFromBuffer helper. If no name is given, the content hash will be used to determine the name.

Example usage

The following example is adapted from the source of gatsby-source-mysql:

`js
// gatsby-node.js
const createMySqlNodes = require(./create-nodes)

exports.sourceNodes = async ({ actions, createNodeId, getCache }, config) => {
const { createNode } = actions
const { conn, queries } = config
const { db, results } = await query(conn, queries)

try {
queries
.map((query, i) => ({ ...query, ___sql: results[i] }))
.forEach(result =>
createMySqlNodes(result, results, createNode, {
createNode,
createNodeId,
getCache,
})
)
db.end()
} catch (e) {
console.error(e)
db.end()
}
}

// create-nodes.js
const { createFileNodeFromBuffer } = require(gatsby-source-filesystem-with-queue)
const createNodeHelpers = require(gatsby-node-helpers).default

const { createNodeFactory } = createNodeHelpers({ typePrefix: mysql })

function attach(node, key, value, ctx) {
if (Buffer.isBuffer(value)) {
ctx.linkChildren.push(parentNodeId =>
createFileNodeFromBuffer({
buffer: value,
getCache: ctx.getCache,
createNode: ctx.createNode,
createNodeId: ctx.createNodeId,
})
)
value = Buffer
}

node[key] = value
}

function createMySqlNodes({ name, __sql, idField, keys }, results, ctx) {
const MySqlNode = createNodeFactory(name)
ctx.linkChildren = []

return __sql.forEach(row => {
if (!keys) keys = Object.keys(row)

const node = { id: row[idField] }

for (const key of keys) {
attach(node, key, row[key], ctx)
}

node = ctx.createNode(node)

for (const link of ctx.linkChildren) {
link(node.id)
}
})
}

module.exports = createMySqlNodes
`

Troubleshooting

In case that due to spotty network, or slow connection, some remote files fail to download. Even after multiple retries and adjusting concurrent downloads, you can adjust timeout and retry settings with these environment variables:

- GATSBY_STALL_RETRY_LIMIT, default: 3
- GATSBY_STALL_TIMEOUT, default: 30000
- GATSBY_CONNECTION_TIMEOUT, default: 30000`