# Lambda Builder

> New as of 0.28.0

The `lambda` builder builds AWS Lambda functions in an environment simulating AWS Lambda runtimes via [lambda-builder](https://github.com/dokku/lambda-builder). Apps built via this builder can run natively in Dokku and may also have their artifacts scheduled to Lambda via an appropriate scheduler.

## Usage

### Detection

This builder will be auto-detected in the following case:

- A `lambda.yml` exists in the root of the app repository.

The builder may also be selected via the `builder:set` command

```shell
dokku builder:set node-js-app selected lambda
```

### Supported languages

The `lambda` builder plugin supports the following AWS runtime languages on Amazon Linux 2:

- dotnet
- go (builder is based on AL1)
- nodejs
- python
- ruby

See the [lambda-builder](https://github.com/dokku/lambda-builder#how-does-it-work) documentation for more information on how specific languages are detected.

### Customizing the build environment

The `lambda` builder plugin delegates all build logic to [lambda-builder](https://github.com/dokku/lambda-builder), including language detection and build/runtime environment specification. The lambda-builder tool supports a `lambda.yml` file format for customizing how apps are built. Please see the readme for lambda-builder for more information on different options.

### Changing the `lambda.yml` location

When deploying a monorepo, it may be desirable to specify the specific path of the `lambda.yml` file to use for a given app. This can be done via the `builder-lambda:set` command. If a value is specified and that file does not exist in the app's build directory, then the build will fail.

```shell
dokku builder-lambda:set node-js-app lambdayml-path lambda2.yml
```

The default value may be set by passing an empty value for the option:

```shell
dokku builder-lambda:set node-js-app lambdayml-path
```

The `lambdayml-path` property can also be set globally. The global default is `lambda.yml`, and the global value is used when no app-specific value is set.

```shell
dokku builder-lambda:set --global lambdayml-path lambda2.yml
```

The default value may be set by passing an empty value for the option.

```shell
dokku builder-lambda:set --global lambdayml-path
```

### Displaying builder-lambda reports for an app

You can get a report about the app's storage status using the `builder-lambda:report` command:

```shell
dokku builder-lambda-json:report
```

```
=====> node-js-app builder-lambda information
       Builder-lambda computed lambdayml path: lambda2.yml
       Builder-lambda global lambdayml path:   lambda.yml
       Builder-lambda lambdayml path:          lambda2.yml
=====> python-sample builder-lambda information
       Builder-lambda computed lambdayml path: lambda.yml
       Builder-lambda global lambdayml path:   lambda.yml
       Builder-lambda lambdayml path:
=====> ruby-sample builder-lambda information
       Builder-lambda computed lambdayml path: lambda.yml
       Builder-lambda global lambdayml path:   lambda.yml
       Builder-lambda lambdayml path:
```

You can run the command for a specific app also.

```shell
dokku builder-lambda:report node-js-app
```

```
=====> node-js-app builder-lambda information
       Builder-lambda computed lambdayml path: lambda2.yml
       Builder-lambda global lambdayml path:   lambda.yml
       Builder-lambda lambdayml path:          lambda2.yml
```

You can pass flags which will output only the value of the specific information you want. For example:

```shell
dokku builder-lambda:report node-js-app --builder-lambda-lambdayml-path
```

```
lambda2.yml
```