Swiftpack.co - suborbital/reactr as Swift Package

Swiftpack.co is a collection of thousands of indexed Swift packages. Search packages.
suborbital/reactr v0.12.0
Function scheduler for Go & WebAssembly
⭐️ 134
🕓 7 weeks ago
.package(url: "https://github.com/suborbital/reactr.git", from: "v0.12.0")


Reactr is a fast, performant function scheduling library. Reactr is designed to be flexible, with the ability to run embedded in your Go applications and first-class support for WebAssembly.

Reactr runs functions called Runnables, and transparently spawns workers to process jobs. Each worker processes jobs in sequence, using Runnables to execute them. Reactr jobs are arbitrary data, and they return arbitrary data (or an error). Jobs are scheduled, and their results can be retrieved at a later time.


Reactr has support for Wasm-packaged Runnables. The rwasm package contains a multi-tenant Wasm scheduler, an API to grant capabilities to Wasm Runnables, and support for several languages including Rust (stable), TypeScript/AssemblyScript (beta), and Swift (alpha). See Wasm and the Subo CLI for details.

The Basics

First, install Reactr's core package rt:

go get github.com/suborbital/reactr/rt

And then get started by defining something Runnable:

package main

import (


type generic struct{}

// Run runs a generic job
func (g generic) Run(job rt.Job, ctx *rt.Ctx) (interface{}, error) {
	fmt.Println("doing job:", job.String()) // get the string value of the job's data

	// do your work here

	return fmt.Sprintf("finished %s", job.String()), nil

// OnChange is called when Reactr starts or stops a worker to handle jobs,
// and allows the Runnable to set up before receiving jobs or tear down if needed.
func (g generic) OnChange(change rt.ChangeEvent) error {
	return nil

A Runnable is something that can take care of a job, all it needs to do is conform to the Runnable interface as you see above.

Once you have a Runnable, create a Reactr instance, register it, and Do some work:

package main

import (


func main() {
	r := rt.New()

	r.Register("generic", generic{})

	result := r.Do(r.Job("generic", "hard work"))

	res, err := result.Then()
	if err != nil {

	fmt.Println("done!", res.(string))

When you Do some work, you get a Result. A result is like a Rust future or a JavaScript promise, it is something you can get the job's result from once it is finished.

Calling Then() will block until the job is complete, and then give you the return value from the Runnable's Run. Cool, right?

Reactr has some very powerful capabilities, visit the Reactr guide to learn more.

Reactr is being actively developed and has planned improvements, including optimized memory usage, library stability, data persistence, and more. Cheers!

Copyright Suborbital contributors 2021


Stars: 134
Last commit: 2 hours ago

Ad: Job Offers

iOS Software Engineer @ Perry Street Software
Perry Street Software is Jack’d and SCRUFF. We are two of the world’s largest gay, bi, trans and queer social dating apps on iOS and Android. Our brands reach more than 20 million members worldwide so members can connect, meet and express themselves on a platform that prioritizes privacy and security. We invest heavily into SwiftUI and using Swift Packages to modularize the codebase.

Submit a free job ad (while I'm testing this). The analytics numbers for this website are here.

Release Notes

7 weeks ago

Improved WASI support, Redis cache, and more!

Beta-12 of Reactr brings some improvements and some new abilities:

  • Improved compatibility with standard WASI modules by calling the standard _start function to initialize the module (the now-deprecated init is still called if _start is not present).
  • Added support for Redis as a cache backend for the cache capability. Use CacheConfig when creating the Reactr instance to configure the Redis connection, and it will be used for all Wasm Runnables.
  • Added the ability to autoscale the work threads used to handle Reactr jobs. This makes Reactr much more flexible when working with large spikes in traffic.
  • Updated the internal Wasm runtime to latest avaialble.

Swiftpack is being maintained by Petr Pavlik | @ptrpavlik | @swiftpackco | API | Analytics