Creating a New CloudQuery Source Plugin in JavaScript
This guide will help you develop a new source or destination plugin for CloudQuery in JavaScript. CloudQuery's modular architecture means that a source plugin can be used to fetch data from any third-party API, and then be combined with a destination plugin to insert data into any supported destination. We will cover the basics of how to get started, and then dive into some more advanced topics. We will also cover how to release your plugin for use by the wider CloudQuery community.
This guide assumes that you are somewhat familiar with CloudQuery. If you are not, we recommend starting by reading the Quickstart guide and playing around with the CloudQuery CLI a bit first.
Though you by no means need to be an expert, you will also need some familiarity with JavaScript and Node.js. If you are new to JavaScript or Node.js, we recommend starting with the official Node.js tutorial (opens in a new tab).
The JavaScript SDK emits TypeScript type definitions, and we'll refer to those throughout this guide. If you are not familiar with TypeScript, you can read more about it here (opens in a new tab).
Core Concepts
Before we dive in, let's quickly cover some core concepts of CloudQuery plugins, so that they're familiar when we see our first example.
Syncs
A sync is the process that gets kicked off when a user runs cloudquery sync. A sync is responsible for fetching data from a third-party API and inserting it into the destination (database, data lake, stream, etc.). When you write a source plugin for CloudQuery, you will only need to implement the part that interfaces with the third-party API. The rest of the sync process, such as delivering to the destination database, is handled by the CloudQuery SDK.
Tables and Services
A table is the term CloudQuery uses for a collection of related data. In most databases it directly maps to an actual database table, but in some destinations it could be stored as a file, stream or other medium. A table is defined by a name, a list of columns, and a resolver function. The resolver function is responsible for fetching data from the third-party API and sending it to CloudQuery. We will look at examples of this soon!
Every table will typically have its own .js file inside the plugin tables directory.
Resolvers
Resolvers are functions associated with a table that get called when it's time to populate data for that table. There are two types of resolvers:
Table resolvers
Table resolvers are responsible for fetching data from the third-party API. In JavaScript, a table resolver in an object that matches the TableResolver (opens in a new tab) TypeScript type. For top-level tables, resolve will only be called once per multiplexer client. For dependent tables, the resolver will be called once for each parent row, and the parent resource will be passed in as well. (More on this, and multiplexers, shortly.)
Column resolvers
Column resolvers (opens in a new tab) are responsible for mapping data from the third-party API into the columns of the table. In most cases, you will not need to implement this, as the SDK will automatically map data from the struct passed in by the table resolver to the columns of the table. But in some cases, you may need to implement a custom column resolver to fetch additional data or do custom transformations.
Multiplexers
Multiplexers (opens in a new tab) are a way to parallelize the fetching of data from the third-party API. Some top-level tables require multiple calls to fetch all their data. For example, a sync for the GitHub source plugin that fetches data for multiple organizations, will need to make one call per organization to list all repositories. By multiplexing over organizations, these top-level queries can also be done in parallel. Each table defines the multiplexer that it should use. The CloudQuery plugin SDK will then call the table resolver once for each client in the multiplexer. Many plugins will not need to use multiplexers, but they are useful for plugins that need to fetch data for multiple accounts, organizations, or other entities.
Apache Arrow JavaScript SDK
Like other CloudQuery SDK the JavaScript SDK uses [Apache Arrow] as part of the underlying CloudQuery type system.
When writing a source plugin you should not install the Apache JavaScript SDK via npm and instead use the version of the SDK that is bundled with the CloudQuery JavaScript SDK for maximum compatibility.
See example in the Airtable plugin (opens in a new tab).
Creating Your First Plugin
As the JavaScript SDK is still new, we don't yet have a plugin scaffold generator. For now, we recommend starting by copying the code from an existing JavaScript plugin (opens in a new tab).
Before running the plugin locally, you will need to install its dependencies:
npm ciIf you copied a reference plugin, this will include the CloudQuery plugin SDK. If you are starting from scratch, you will need to install the SDK separately:
npm i @cloudquery/plugin-sdk-javascriptTesting the Plugin
There are two options for running a plugin before as a developer before it is released: as a gRPC server, or as a standalone binary. We will briefly summarize both options here, or you can read about them in more detail in Running Locally.
Run the Plugin as a gRPC Server
This mode is especially useful for setting breakpoints your code for debugging, as you can run it in server mode from your IDE and attach a debugger to it. To run the plugin as a gRPC server, you can run the following command in the root of the plugin directory:
# Assuming you copied a reference plugin
npm run dev
# Or if you are starting from scratch
node 'path-to-main-node-file' serveThis will start a gRPC server on port 7777. You can then create a config file that sets the registry and path properties to point to this server. For example:
kind: source
spec:
name: "my-plugin"
registry: "grpc"
path: "localhost:7777"
version: "v1.0.0"
tables:
["*"]
destinations:
- "sqlite"
---
kind: destination
spec:
name: sqlite
path: cloudquery/sqlite
registry: cloudquery
version: "v2.8.6"
spec:
connection_string: ./db.sqlWith the above configuration, we can now run cloudquery sync as normal:
cloudquery sync config.yamlNote that when running a source plugin as a gRPC server, errors with the source plugin will be printed to the console running the gRPC server, not to the CloudQuery log like usual.
Run the Plugin as a Docker Container
You can also build a Docker container for the plugin, and then either run it directly as a gRPC server or via the docker registry in a config file. See an example Docker file for a JavaScript plugin here (opens in a new tab).
We need to first build the image:
docker build -t my-plugin:latest .And then we can specify the docker registry in our config file:
kind: source
spec:
name: "my-plugin"
registry: "docker"
path: "my-plugin:latest"
tables:
["*"]
destinations:
- "sqlite"
---
kind: destination
spec:
name: sqlite
path: cloudquery/sqlite
version: "v2.8.6"
spec:
connection_string: ./db.sqlReleasing and Deploying Your Plugin
Releasing a JavaScript plugin for use by the wider CloudQuery community involves publishing a Docker image to any registry of your choice. We recommend using Docker Hub (opens in a new tab), but you can also use GitHub Container Registry (opens in a new tab) or any other registry that supports Docker images. The entrypoint should be node 'path-to-main-node-file'. You can see an example Dockerfile here (opens in a new tab).
Once published, users can then import your plugin by specifying the image path in their config file together with the docker registry, e.g.:
kind: source
spec:
name: cloudwidgets
path: ghcr.io/myorg/cloudwidgets
registry: dockerThis will download and run the plugin as a Docker container when cloudquery sync is run.
Real-world Examples
A good way to learn how to create a new plugins in JavaScript is to look at the following examples:
- The Airtable Source Plugin (opens in a new tab) is an example of dynamically generating tables based on the schema of a third-party API and mapping API types to arrow types.
