Nomad Codebase Documentation
===

This directory contains some documentation about the Nomad codebase,
aimed at readers who are interested in making code contributions.

If you're looking for information on _using_ Nomad, please instead refer
to the [Nomad website](https://nomadproject.io).

Developing with Vagrant
---
A development environment is supplied via Vagrant to make getting started easier.

1. Install [Vagrant](https://www.vagrantup.com/docs/installation)
1. Install [Virtualbox](https://www.virtualbox.org/)
1. Bring up the Vagrant project
    ```sh
    $ git clone https://github.com/hashicorp/nomad.git
    $ cd nomad
    $ vagrant up
    ```

    The virtual machine will launch, and a provisioning script will install the
    needed dependencies within the VM.

1. SSH into the VM
    ```sh
    $ vagrant ssh
    ```

Developing without Vagrant
---
1. Install [Go 1.21.5+](https://golang.org/) *(Note: `gcc-go` is not supported)*
1. Clone this repo
   ```sh
   $ git clone https://github.com/hashicorp/nomad.git
   $ cd nomad
   ```
1. Bootstrap your environment
   ```sh
   $ make bootstrap
   ```
1. (Optionally) Set a higher ulimit, as Nomad creates many file handles during normal operations
   ```sh
   $ [ "$(ulimit -n)" -lt 1024 ] && ulimit -n 1024
   ```
1. Verify you can run smoke tests
   ```sh
   $ make test
   ```
   **Note:** You can think of this as a `smoke` test which runs a subset of
   tests and some may fail because of `operation not permitted` error which
   requires `root` access. You can use `go test` to test the specific subsystem
   which you are working on and let the CI run rest of the tests for you.

Running a development build
---
1. Compile a development binary (see the [UI README](https://github.com/hashicorp/nomad/blob/main/ui/README.md) to include the web UI in the binary)
    ```sh
    $ make dev
    # find the built binary at ./bin/nomad
    ```
1. Start the agent in dev mode
    ```sh
    $ sudo bin/nomad agent -dev
    ```
1. (Optionally) Run Consul to enable service discovery and health checks
    1. Download [Consul](https://www.consul.io/downloads)
    1. Start Consul in dev mode
        ```sh
        $ consul agent -dev
        ```

Compiling Protobufs
---
If in the course of your development you change a Protobuf file (those ending in .proto), you'll need to recompile the protos.

1. Run `make boostrap` to install the [`buf`](https://github.com/bufbuild/buf)
   command.
1. Compile Protobufs
    ```sh
    $ make proto
    ```

Building the Web UI
---
See the [UI README](https://github.com/hashicorp/nomad/blob/main/ui/README.md) for instructions.

Create a release binary
---
To create a release binary:

```sh
$ make prerelease
$ make release
$ ls ./pkg
```

This will generate all the static assets, compile Nomad for multiple
platforms and place the resulting binaries into the `./pkg` directory.

API Compatibility
--------------------
Only the `api/` and `plugins/` packages are intended to be imported by other projects. The root Nomad module does not follow semver and is not intended to be imported directly by other projects.

## Architecture

The code for Nomad's major components is organized as:

* `api/` provides a Go client for Nomad's HTTP API.
* `client/` contains Nomad's client agent code.
* `command/` contains Nomad's CLI code.
* `nomad/` contains Nomad's server agent code.
* `ui/` contains Nomad's UI code.
* `website/` contains Nomad's website and documentation.

The high level control flow for many Nomad actions (via the CLI or UI) are:

```
# Read actions:
Client -> HTTP API -> RPC -> StateStore

# Actions that change state:
Client -> HTTP API -> RPC -> Raft -> FSM -> StateStore
```

Checklists
---

When adding new features to Nomad there are often many places to make changes.
It is difficult to determine where changes must be made and easy to make
mistakes.

The following checklists are meant to be copied and pasted into PRs to give
developers and reviewers confidence that the proper changes have been made:

* [New `jobspec` entry](checklist-jobspec.md)
* [New CLI command](checklist-command.md)
* [New RPC endpoint](checklist-rpc-endpoint.md)

Tooling
---

* [Go tool versions](golang.md)