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Builder Management

New as of 0.24.0

builder:report [<app>] [<flag>]   # Displays a builder report for one or more apps
builder:set <app> <key> (<value>) # Set or clear a builder property for an app

Builders are a way of customizing how an app is built from a source, allowing users flexibility in how artifacts are created for later scheduling.

Usage

Builder selection

Dokku supports the following built-in builders:

Builders run a detection script against a source code repository, and the first detected builder will be used to build the app artifact. The exception to this is when a Dockerfile is detected and the app is also able to use either herokuish or pack-cli for building, in which case one of the latter will be chosen.

Overriding the auto-selected builder

If desired, the builder can be specified via the builder:set command by speifying a value for selected. The selected builder will always be used.

dokku builder:set node-js-app selected dockerfile

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

dokku builder:set node-js-app selected

The selected property can also be set globally. The global default is an empty string, and auto-detection will be performed when no value is set per-app or globally.

dokku builder:set --global selected herokuish

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

dokku builder:set --global selected

Displaying builder reports for an app

You can get a report about the app's builder status using the builder:report command:

dokku builder:report
=====> node-js-app builder information
       Builder computed selected: herokuish
       Builder global selected: herokuish
       Builder selected: herokuish
=====> python-sample builder information
       Builder computed selected: dockerfile
       Builder global selected: herokuish
       Builder selected: dockerfile
=====> ruby-sample builder information
       Builder computed selected: herokuish
       Builder global selected: herokuish
       Builder selected:

You can run the command for a specific app also.

dokku builder:report node-js-app
=====> node-js-app builder information
       Builder selected: herokuish

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

dokku builder:report node-js-app --builder-selected

Custom builders

To create a custom builder, the following triggers must be implemented:

  • builder-build:
    • arguments: BUILDER_TYPE APP SOURCECODE_WORK_DIR
    • description: Creates a docker image named with the output of common#get_app_image_name $APP.
  • builder-detect:
    • arguments: APP SOURCECODE_WORK_DIR
    • description: Outputs the name of the builder (without the builder- prefix) to use to build the app.
  • builder-release:
    • arguments: BUILDER_TYPE APP IMAGE_AG
    • description: A post-build, pre-release trigger that can be used to post-process the image. Usually simply tags and labels the image appropriately.

Custom plugins names must have the prefix builder- or builder overriding via builder:set may not function as expected.

Builders can use any tools available on the system to build the docker image, and may even be used to schedule building off-server. The only current requirement is that the image must exist on the server at the end of the builder-build command, though this requirement may be relaxed in a future release.

For a simple example of how to implement this trigger, see builder-pack, which utilizes a cli tool - pack-cli - to generate an OCI image that is compatible with Docker and can be scheduled by the official scheduling plugins.

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