flamenco/README.md

# Flamenco 3

This repository contains the sources for Flamenco 3. The Manager, Worker, and
Blender add-on sources are all combined in this one repository.

## Using Shaman on Windows

The Shaman storage system uses _symbolic links_. On Windows the creation of symbolic links requires a change in security policy. Follow these steps:

1. Press Win+R, in the popup type `secpol.msc`. Then click OK.
2. In the _Local Security Policy_ window that opens, go to _Security Settings_ > _Local Policies_ > _User Rights Assignment_.
3. In the list, find the _Create Symbolic Links_ item.
4. Double-click the item and add yourself (or the user running Flamenco Manager or the whole users group) to the list.
5. Log out & back in again, or reboot the machine.


## Building

1. Install [Go 1.18 or newer](https://go.dev/), and Node 16 (see "Node / Web UI" below).
2. Optional: set the environment variable `GOPATH` to where you want Go to put its packages.
3. Ensure `$GOPATH/bin` is included in your `$PATH` environment variable. `$GOPATH` defaults to `$HOME/go` if not set. Run `go env GOPATH` if you're not sure.
4. Set up the web frontend for development (see "Node / Web UI" below).
5. Run `make with-deps` to install build-time dependencies and build the application. Subsequent builds can just run `make` without arguments.

You should now have two executables: `flamenco-manager` and `flamenco-worker`.
Both can be run with the `-help` CLI argument to see the available options.

To rebuild only the Manager or Worker, run `make flamenco-manager` or `make flamenco-worker`.


## Node / Web UI

The web UI is built with Vue, Bootstrap, and Socket.IO for communication with the backend. NodeJS/NPM is used to collect all of those and build the frontend files. It's recommended to install Node v16 via Snap:

```
sudo snap install node --classic --channel=16
```

This also gives you the Yarn package manager, which can be used to install web dependencies and build the frontend files via:

```
make webapp
```

Then run the frontend development server with:

```
yarn --cwd web/app run dev --host
```

The `--host` parameter is optional but recommended. The downside is that it
exposes the devserver to others on the network. The upside is that it makes it
easier to detect configuration issues. The generated OpenAPI client defaults to
using `localhost`, and if you're not testing on `localhost` this stands out
more.

The web interface is also "baked" into the `flamenco-manager` binary when using
`make flamenco-manager`.


## Generating Code

Some code (Go, Python, JavaScript) is generated from the OpenAPI specs in
`pkg/api/flamenco-openapi.yaml`. There are also Go files generated to create
mock implementations of interfaces for unit testing purposes.

Generated code is committed to Git, so that after a checkout you shouldn't
need to re-run the generator to build Flamenco.

The JavaScript & Python generator is made in Java, so it requires a JRE/JDK to
be installed. On Ubuntu Linux, `sudo apt install default-jre-headless` should be
enough.

The following files & directories are generated. Generated directories are
completely erased before regeneration, so do not add any files there manually.

- `addon/flamenco/manager/`: Python API for the Blender add-on.
- `pkg/api/*.gen.go`: Go API shared by Manager and Worker.
- `internal/**/mocks/*.gen.go`: Generated mocks for Go unit tests.
- `web/app/src/manager-api/`: JavaScript API for the web front-end.


## OpenAPI Commit Guidelines

Typically a change to the OpenAPI definition consists of three steps, namely
making the change to the OpenAPI file, regenerating code, and then alter
whatever manually-written code needs altering.

Each of these steps should be **committed independently**, by following these
steps:

1. Commit the changes to `pkg/api/flamenco-openapi.yaml`, prefixing the commit
   message with `OAPI:`.
2. Regenerate code with `make generate`, then commit with message
   `OAPI: Regenerate code`.
3. Commit any other code changes to complete the change.

The downside to this approach is that the second commit will likely break the
project, which is unfortunate. However, this approach does have some advantages:

- The regenerated code has the commit hash of the actual change to the OpenAPI
  definition.
- Changes to manually-written and generated code are tracked in separate
  commits. This makes them easier to comprehend by humans.


## Swagger UI

Flamenco Manager has a SwaggerUI interface at http://localhost:8080/api/v3/swagger-ui/


## SocketIO

[SocketIO v2](https://socket.io/docs/v2/) is used for sending updates from
Flamenco Manager to the web frontend. Version 2 of the protocol was chosen,
because that has a mature Go server implementation readily available.

SocketIO messages have an _event name_ and _room name_.

- **Web interface clients** send messages to the server with just an _event
  name_. These are received in handlers set up by
  `internal/manager/webupdates/webupdates.go`, function
  `registerSIOEventHandlers()`.
- **Manager** typically sends to all clients in a specific _room_. Which client
  has joined which room is determined by the Manager as well. By default every
  client joins the "job updates" and "chat" rooms. This is done in the
  `OnConnection` handler defined in `registerSIOEventHandlers()`.
- Received messages (regardless of by whom) are handled based only on their
  _event name_. The _room name_ only determines _which_ client receives those
  messages.


## Database

Flamenco Manager and Worker use SQLite as database, and Gorm as
object-relational mapper.

Since SQLite has limited support for altering table schemas, migration requires
copying old data to a temporary table with the new schema, then swap out the
tables. Because of this, avoid `NOT NULL` columns, as they will be problematic
in this process.


## Task Statuses

The following table shows the meaning of the different task statuses:

| Status        | Meaning                                                                   | Next Status                                      |
| ------------- | ------------------------------------------------------------------------- | ------------------------------------------------ |
| `queued`      | Ready to be worked on by a Worker                                         | `active`, `canceled`                             |
| `active`      | Assigned to a worker for execution                                        | `completed`, `canceled`, `failed`, `soft-failed` |
| `soft-failed` | Same as `queued`, but has been failed by a worker in an earlier execution | `completed`, `failed`, `canceled`                |
| `completed`   | Worker executed the task succesfully                                      | `requeued`                                       |
| `paused`      | Not yet implemented                                                       |                                                  |

## License

Flamenco is licensed under the GPLv3+ license.