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Julia on Miren

Julia isn't auto-detected, so you deploy it with a Dockerfile.miren. This guide uses HTTP.jl directly; the same pattern works for Genie or Oxygen.

Let your agent do this

Ask your AI coding agent to "set up this Julia app on Miren" after installing the Miren agent skills. It adds the Dockerfile.miren, confirms the server binds 0.0.0.0:$PORT, and deploys — using this page as its reference.

Do you need a Dockerfile?​

Yes. Miren doesn't auto-detect Julia, so add a Dockerfile.miren to your project root. Miren builds from it instead of guessing the stack — see Using Dockerfile.miren.

Want native support?

Miren auto-detects and builds common stacks (Python, Node, Bun, Go, Ruby, Rust) without a Dockerfile. This language isn't one of them yet — if you'd like first-class support, request it.

Bind to the injected port​

Miren injects PORT and routes traffic to it, so read PORT and bind 0.0.0.0:

using HTTP

port = parse(Int, get(ENV, "PORT", "8080"))
println("listening on 0.0.0.0:$port")

HTTP.serve("0.0.0.0", port) do req
    HTTP.Response(200, "Hello from Julia on Miren!\n")
end

The Dockerfile​

Create Dockerfile.miren in your project root. Install and precompile packages during the build so startup is fast:

FROM julia:1.10

WORKDIR /app
RUN julia -e 'using Pkg; Pkg.add("HTTP"); using HTTP'
COPY . /app

EXPOSE 8080
Cold-start compile

Julia JIT-compiles on first use, so the first request after an instance starts is slower than later ones. Precompiling in the build (using HTTP) reduces this. For heavier apps, consider PackageCompiler.jl to bake a sysimage.

.dockerignore​

.git

Set up the app​

Even with a Dockerfile.miren, Miren needs at least one service defined — it doesn't use the image's CMD as the start command. Add a Procfile:

web: julia /app/app.jl

Then create .miren/app.toml naming your app and deploy from your project root:

name = "julia-bench"
miren deploy
Deploying without a service fails

If no service is defined, the build succeeds but the deploy stops with no services defined: please define at least one service in a Procfile or .miren/app.toml.

Environment variables​

Set variables with miren env set — -e for plain values, -s for secrets (masked in output and logs). Read them with ENV["KEY"] or get(ENV, "KEY", default):

miren env set -e JULIA_NUM_THREADS=4
miren env set -s DATABASE_URL

You can also declare variables in .miren/app.toml:

[[env]]
key = "DATABASE_URL"
value = ""
required = true
sensitive = true

See App Configuration — Environment Variables.

Agent quick reference​

  • Detection: none — requires Dockerfile.miren
  • Base image: julia:1.10; Pkg.add + using in the build to precompile
  • Service is required: define a Procfile (web: julia /app/app.jl) — the image CMD is not used
  • Port: get(ENV, "PORT", "8080"); HTTP.serve("0.0.0.0", port)
  • Cold start: JIT compiles on first request; precompile in build or use PackageCompiler.jl
  • Env vars: miren env set -e/-s; read with ENV["KEY"]

Next steps​