Skip to main content

Constellations

Sat is designed to run in a constellation, i.e. a meshed cluster of instances. This enables very interesting network topologies which can run applications in massively distributed and 'edge' environments. The Sat project includes the constd tool, which is a companion constellation manager that can run Atmo applications using a Sat constellation.

Atmo applications are comprised of several functions that coordinate to create a backend system. Since these projects are declarative, it is possible to distribute the app's compute and let the constellation figure out how to efficiently execute your application. That's the goal of constd.

constd uses two main components to run your application:

  • Sat, a small and fast WebAssembly server
  • atmo-proxy, an application-aware router

Build and run constd​

You'll need Go (and optionally Docker) to run Sat and constd, and you'll need to clone the Sat and Atmo repos.

To get started, build atmo-proxy. In the Atmo repo, run:

make atmo/proxy

This installs atmo-proxy into your GOBIN.

Next, in the Sat repo, build constd:

make constd/install

Now launch constd by providing the path to a Runnable Bundle:

CONSTD_EXEC_MODE=metal constd {absolute/path/to}/atmo/example-project/runnables.wasm.zip

constd will launch atmo-proxy and a constellation of Sat instances. Make a request to test it:

curl localhost:8080/hello -d 'my friend'

atmo-proxy receives the request, and proxies execution of the WebAssembly functions to the Sat constellation.

Currently, the following features normally found in an Atmo project won't work very well:

  • Access to cache
  • Authentication for HTTP/GraphQL requests
  • Access to static files
  • Access to databases

But these will come in time!