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Conn3x

Kotlin

Conn3x grade

A Conn3x circuit that puts one exact Kotlin compiler on your hosts, from the zip JetBrains attaches to each GitHub release, checked against its SHA-256. You get kotlinc and kotlin, 2.4.21 by default, the same on every distribution.

You bring the Java. The compiler is a JVM program, and which JDK a host runs is a decision that belongs elsewhere, so this circuit needs a java on the PATH and stops with a clear message if there isn’t one. circuit-java is the easy way, and what the usage below shows. The runtime it installs by default is enough to compile and run.

Usage

Section titled “Usage”
module "java" {
  source = "github.com/conn3xorg/circuit-java?ref=v0.1.0"


  hosts                = { build1 = "203.0.113.10" }
  ssh_private_key_file = "~/.ssh/id_ed25519"
}


module "kotlin" {
  source = "github.com/conn3xorg/circuit-kotlin?ref=v0.1.0"


  hosts                = { build1 = "203.0.113.10" }
  ssh_private_key_file = "~/.ssh/id_ed25519"


  depends_on = [module.java]
}

Then run conn3x init and conn3x apply. A second conn3x plan says No changes.

For hosts created in the same plan, pass host objects with the host key you generated, so Conn3x checks it without a known_hosts entry:

hosts = {
  for name, d in digitalocean_droplet.app : name => {
    address  = d.ipv4_address
    host_key = tls_private_key.host[name].public_key_openssh
  }
}

To try it on a throwaway container first, see examples/local.

Changing the release

Section titled “Changing the release”

kotlin_version and checksum move together. Each release has kotlin-compiler-VERSION.zip.sha256 beside the zip on GitHub. A zip that doesn’t match its checksum fails the apply. Each release gets its own directory, so the new one unpacks beside the old, and kotlin and kotlinc move over to it.

What it does

Section titled “What it does”

On each host, in order:

  1. Stops if java isn’t on the PATH.
  2. Installs curl and unzip.
  3. Downloads kotlin-compiler-VERSION.zip to /opt/kotlin, keeping it only if its SHA-256 matches.
  4. Unpacks it to /opt/kotlin/VERSION/kotlinc.
  5. Links kotlin and kotlinc into /usr/local/bin.

What it doesn’t do

Section titled “What it doesn’t do”
  • It doesn’t install Java, Gradle or Maven. Most Kotlin projects build with one of those, and those fetch their own compiler. This circuit is for hosts that call kotlinc directly.
  • It doesn’t install Kotlin/Native or the other tools in the zip’s bin beyond those two commands. They stay in /opt/kotlin/VERSION/kotlinc/bin.
  • It doesn’t uninstall anything. An old release’s directory and zip, and the whole install when you delete the module, stay on the host.

Inputs

Section titled “Inputs”
Name Type Default Description
hosts any Required Hosts to configure, by name. Each value is an address, such as "203.0.113.10", or a host object such as { address = "203.0.113.10", host_key = "ssh-ed25519 AAAA..." }. A host object can also set user, port, private_key_file and jump_hosts. The two forms can be mixed.
ssh_user string "root" User to log in as.
ssh_port number 22 SSH port.
ssh_private_key_file string null Path to a private key. When null, Conn3x uses the SSH agent.
ssh_known_hosts_file string null known_hosts file to check host keys against. When null, ~/.ssh/known_hosts. Not used for a host object with host_key.
ssh_become bool false Run commands as root through sudo. Set it when ssh_user isn’t root.
kotlin_version string "2.4.21" Kotlin release to install. Change checksum with it.
checksum string The zip of 2.4.21 SHA-256 of kotlin-compiler-VERSION.zip.

Outputs

Section titled “Outputs”
Name Description
kotlin_home Directory of the installed compiler on each host, by host name, such as { build1 = "/opt/kotlin/2.4.21/kotlinc" }.

Requirements

Section titled “Requirements”

Requires Conn3x v0.6.10 or later, a java on the PATH (Java 25 is what was tested), a package mirror each host can reach, and outbound HTTPS to github.com. The zip runs on any architecture Java does; amd64 and arm64 were tested.

Tested on

Section titled “Tested on”

Rocky Linux 10, Fedora 45, Ubuntu 24.04 and Debian 13. examples/local was applied to each on arm64, and the second plan had no changes. Each had the Java 25 runtime from circuit-java v0.1.0, and kotlinc compiled a small program that ran under both java -jar and kotlin. CI runs the same checks on amd64.

On an Ubuntu 24.04 droplet and a Rocky Linux 10 droplet with SELinux enforcing, both s-1vcpu-1gb, amd64, each shared with the other circuits of this batch: the same checks passed, and after a reboot the plan had no changes and they still passed.

ssh_become wasn’t exercised: every test logged in as root.

License

Section titled “License”

MPL-2.0. See LICENSE. Kotlin is under the Apache-2.0 license.

Source

Section titled “Source”