react-native-threads

Spawn new react native JavaScript processes for CPU intensive work outside of your main UI JavaScript process.

Despite this package's name, this isn't real 'threading', but rather multi-processing. The main tradeoff of using this library is memory usage, as creating new JS processes can have significant overhead. Be sure to benchmark your app's memory usage and other resources before using this library! Alternative solutions include using runAfterInteractions or the Interaction Manager, and I recommend you investigate those thoroughly before using this library.

Getting started

$ npm install react-native-threads --save

Mostly automatic installation

$ react-native link react-native-threads

Android

For android you will need to make a slight modification to your MainApplication.java
file. In the getPackages method pass in mReactNativeHost to the RNThreadPackage
constructor:

    @Override
    protected List<ReactPackage> getPackages() {
      return Arrays.<ReactPackage>asList(
        new MainReactPackage(),
        new RNThreadPackage(mReactNativeHost)  // <-- Here
      );
    }

Also note that only the official react native modules are available from your
threads (vibration, fetch, etc...). To include additional native modules in your
threads, pass them into the RNThreadPackage constructor after the mReactNativeHost
like this:
new RNThreadPackage(mReactNativeHost, new ExampleNativePackage(), new SQLitePackage())

Manual installation

iOS

  1. In XCode, in the project navigator, right click Libraries ➜ Add Files to [your project's name]
  2. Go to node_modules ➜ react-native-threads and add RNThread.xcodeproj
  3. In XCode, in the project navigator, select your project. Add libRNThread.a to your project's Build Phases ➜ Link Binary With Libraries
  4. Run your project (Cmd+R)<

Android

  1. Open up android/app/src/main/java/[...]/MainActivity.java
  • Add import com.reactlibrary.RNThreadPackage; to the imports at the top of the file
  • Add new RNThreadPackage(mReactNativeHost) to the list returned by the getPackages() method
  • Also note that only the official react native modules are available from your
    threads (vibration, fetch, etc...). To include additional native modules in your
    threads, pass them into the RNThreadPackage constructor after the mReactNativeHost
    like this:
    new RNThreadPackage(mReactNativeHost, new ExampleNativePackage(), new SQLitePackage())
  1. Append the following lines to android/settings.gradle:
    include ':react-native-threads'
project(':react-native-threads').projectDir = new File(rootProject.projectDir, 	'../node_modules/react-native-threads/android')
  2. Insert the following lines inside the dependencies block in android/app/build.gradle:
      compile project(':react-native-threads')

Windows

Windows support is not yet implemented, but PRs are welcome if you want to give it a shot!

Read it! :D

  1. In Visual Studio add the RNThread.sln in node_modules/react-native-threads/windows/RNThread.sln folder to their solution, reference from their app.
  2. Open up your MainPage.cs app
  • Add using Thread.RNThread; to the usings at the top of the file
  • Add new RNThreadPackage() to the List<IReactPackage> returned by the Packages method

Usage

In your application code (react components, etc.):

import { Thread } from 'react-native-threads';

// start a new react native JS process
const thread = new Thread('path/to/thread.js');

// send a message, strings only
thread.postMessage('hello');

// listen for messages
thread.onmessage = (message) => console.log(message);

// stop the JS process
thread.terminate();

In your thread code (dedicated file such as thread.js):

import { self } from 'react-native-threads';

// listen for messages
self.onmessage = (message) => {
}

// send a message, strings only
self.postMessage('hello');

Check out the examples directory in this repo for demos of using react-native-threads
in a functioning app!

Thread Lifecycle

  • Threads are paused when the app enters in the background
  • Threads are resumed once the app is running in the foreground
  • During development, when you reload the main JS bundle (shake device -> Reload) the threads are killed

Debugging

Instantiating Threads creates multiple react native JS processes and can make debugging
remotely behave unpredictably. I recommend using a third party debugging tool like
Reactotron to aid with this. Each process,
including your main application as well as your thread code can connect to Reactotron
and log debugging messages.

Building for Release

You will need to manually bundle your thread files for use in a production release
of your app. This documentation assumes you have a single thread file called
index.thread.js in your project root. If your file is named differently or in
a different location, you can update the documented commands accordingly.

Note: If your single thread file is in a different location, the folder structure needs to
be replicated under ./ios and ./android/app/src/main/assets/threads.

./App/Workers/worker.thread.js => ./ios/App/Workers/worker.thread.jsbundle
./App/Workers/worker.thread.js => ./android/app/src/main/assets/threads/App/Workers/worker.thread.jsbundle

For iOS you can use the following command:

node node_modules/react-native/local-cli/cli.js bundle --dev false --assets-dest ./ios --entry-file index.thread.js --platform ios --bundle-output ./ios/index.thread.jsbundle

Once you have generated the bundle file in your ios folder, you will also need to add
the bundle file to you project in Xcode. In Xcode's file explorer you should see
a folder with the same name as your app, containing a main.jsbundle file as well
as an appDelegate.m file. Right click on that folder and select the 'Add Files to '
option, which will open up finder and allow you to select your ios/index.thread.js
file. You will only need to do this once, and the file will be included in all future
builds.

For Android create this direactory
mkdir ./android/app/src/main/assets/threads

And then you can use the following command:

node node_modules/react-native/local-cli/cli.js bundle --dev false --assets-dest ./android/app/src/main/res/ --entry-file index.thread.js --platform android --bundle-output ./android/app/src/main/assets/threads/index.thread.bundle

For convenience I recommend adding these thread building commands as npm scripts
to your project.

Example App

Included in this repository is a simple example application demonstrating basic
usage of react-native-threads. Look at examples/SimpleExample/README.md for
instructions on running it. Here's how the app looks with the Reactotron debugger:

SimpleExample Screen Capture

Acknowledgements

This library was heavily inspired by two other packages both under the name of
react-native-workers.

The first was https://github.com/fabriciovergal/react-native-workers ,
and the second was https://github.com/devfd/react-native-workers

I ended up going with devfd's implementation strategy as it seemed more flexible
and feature-rich to me. At the time of this writing neither library was functioning
on the latest version of react native, and neither seemed to be very actively maintained.

This library would not exist without those two reference implementations to guide me!

GitHub