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Duct

Duct is a highly modular framework for building server-side applications in Clojure using data-driven architecture.

It is similar in scope to Arachne, and is based on Integrant. Duct builds applications around an immutable configuration that acts as a structural blueprint. The configuration can be manipulated and queried to produce sophisticated behavior.

Upgrading

See: UPGRADING.md.

Quick Start

To create a new Duct project with Leiningen:

lein new duct <your project name>

This will create a minimal Duct project. You can extend this by appending profile hints to add extra functionality.

  • +api adds API middleware and handlers
  • +ataraxy adds the Ataraxy router
  • +cljs adds in ClojureScript compilation and hot-loading
  • +example adds an example handler
  • +heroku adds configuration for deploying to Heroku
  • +postgres adds a PostgreSQL dependency and database component
  • +site adds site middleware, a favicon, webjars and more
  • +sqlite adds a SQLite dependency and database component

For example:

lein new duct foobar +site +example

As with all Leiningen templates, Duct will create a new directory with the same name as your project. For information on how to run and build your project, refer to the project's README.md file.

Concepts

The structure of the application is defined by an Integrant configuration map.

In development, Duct uses Stuart Sierra's Reloaded Workflow.

In production, Duct follows the Twelve-Factor App methodology.

Local state is preferred over global state.

Namespaces should group functions by purpose, rather than by layer.

Protocols should be used to wrap external APIs.

Structure

Duct adds a layer of abstraction on top of Integrant. In Integrant, a configuration map is initiated into a running system map.

┌────────┐   ┌────────┐
│ config ├──>│ system │
└────────┘   └────────┘

In Duct, the configuration is initiated twice. The configuration is first initiated into an intermediate configuration, which in turn is initiated into the system:

┌────────┐   ┌──────────────┐   ┌────────┐
│ config ├──>│ intermediate ├──>│ system │
└────────┘   └──────────────┘   └────────┘

In the same way that higher-order functions allow us to abstract common patterns of code, Duct's layered configurations allow us to abstract common patterns of configuration.

Keys in a Duct configuration are expected to initiate into functions that transform a configuration map. There are two broad types: profiles, which merge their value into the configuration, and modules, which provide more complex manipulation.

Documentation

Community

File structure

Duct projects are structured as below. Files marked with a * are kept out of version control.

{{project}}
├── README.md
├── dev
│   ├── resources
│   │   ├── dev.edn
│   │   └── local.edn *
│   └── src
│       ├── dev.clj
│       ├── local.clj *
│       └── user.clj
├── profiles.clj
├── project.clj
├── resources
│   └── {{project}}
│       └── config.edn
├── src
│   ├── duct_hierarchy.edn
│   └── {{project}}
│       └── main.clj
└── test
    └── {{project}}

License

Copyright © 2019 James Reeves

Distributed under the MIT license.