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suborbital/reactr v0.15.3-beta1
Function scheduler for Go & WebAssembly
⭐️ 289
🕓 14 weeks ago
.package(url: "https://github.com/suborbital/reactr.git", from: "v0.15.3-beta1")

Reactr has been deprecated. You can use the new scheduler and engine packages, which are a drop-in replacements for this project. You can find the docs in this repo.

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 engine 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?

Copyright Suborbital contributors 2021


Stars: 289
Last commit: 3 weeks ago
jonrohan Something's broken? Yell at me @ptrpavlik. Praise and feedback (and money) is also welcome.

Release Notes

1 year ago


Update wasmtime to v0.35.0

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