ELI5: Watchman – Awaiting Modifications to Construct Sooner

In this post, we’re talking about a project called Watchman, which is a file monitoring service. If you’d like to see a video about Watchman, visit the YouTube Open Source YouTube Channel.

Why Guardian?

Web development has changed dramatically over the past decade. Let’s consider what it takes to develop and deploy a web app today. After your changes have been deployed, your web application must rebuild itself. The creation process usually involves mapping routes and file paths, traversing JavaScript and CSS sources, and processing hundreds, sometimes even thousands, of node packages. It would take a huge web app like Facebook to build their website from scratch, especially over and over again. Also, why should you rebuild the entire site when you’ve only changed a handful of files? With Watchman, developers can focus on managing the files they worked on in the web app development process. This approach is also known as an incremental build.

Watchman is a file monitoring service with clients for a command line, NodeJS, and more. It records all changes and triggers assigned actions. In the example with the Facebook app, Watchman would have ensured that only files that are changed or influenced by our developers are updated. We previously shared how this service reduced build time by 60% in some cases!

Beyond the build system, Watchman has been updated to support other use cases. It can log changes, trigger test-suites, transform files and much more. Watchman has also been updated to support a wide variety of operating systems, including Windows.

Where is it used?

Watchman was first made available as an open source version by Facebook in 2013. Since then, Watchman has been used daily by our developers on Facebook. It has also been incorporated into many other open source projects such as React Native and Buck.

Where can i learn more?

To learn more about Watchman, visit their website. The project has an excellent starter and extensive documentation. The project has an active community chat on Freenode and StackOverflow. If you run into a problem, there is also a troubleshooting page on the project website.

If you have any thoughts or questions about Watchman, please let us know on our YouTube channel or tweet us at.

About the ELI5 series

In a series of short videos (around 1 minute long) one of our developer attorneys on the Facebook Open Source team explains a Facebook Open Source project in a way that is easy to understand and use.

For each of these videos we are writing an accompanying blog post (like the one you are reading right now), which you can find on our YouTube channel.

To learn more about Facebook Open Source, visit our Open Source website, subscribe to our YouTube channel, or follow us on Twitter and Facebook.

Would you like to work with open source on Facebook? Check out our open source related job postings on our careers page by taking this short survey.

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