An example Julia webserver configuration which can be hosted on services such as Render or Fly.io This example is very basic, it allows you to create super fast servers for very specific purposes. If you prefer a fully fledged Model View Controller (MVC) application, then take a look at Genie.jl.

This example repository works as follows. Let's say that we create an app called MyApp. The source code for the app is located in src/MyApp.jl. To be able to run it quickly, we need to use PackageCompiler.jl to compile packages. Otherwise, it might take 10 seconds or more for the server to start responding after a server restart which is not acceptable for a microservice. The power of microservices is that they can quickly be restarted. Okay, so how much do we compile? We could choose to compile all dependencies, but that would mean that everything needs to be re-compiled once our app changes. So, as a trade off, this example repository compiles only the dependencies of MyApp. This should be quick enough for most cases. As a side-note, to speed up the app itself once that is necessary, run the app's code when the module is loaded. This will cause some of the MyApp code to be covered by the precompilation and can take about 50% from the running time. See, also Makie.jl/src/precompiles.jl.

Anyway, back to the code. The Dockerfile shows how the docker is created. The file creates the sysimage and configures a starting point to start the server. Here, build-sysimage.jl will compile all direct dependencies of MyApp and run scripts/precompile-execution.jl. In the execution file, a HTTP server is started and closed again. Running such a simple server causes much of the HTTP.jl code to be compiled which greatly reduces the time to first response.

To deploy this code on Render.com, copy this repository and link it to your Render account. After about 10 minutes of building a Docker container, Render will run this example server online. You can then visit the site and see a webpage. If you push changes to MyApp, they will be visible within a few minutes.

Instructions for Fly.io are similar.