metosin/palikka

Name: palikka

Owner: Metosin

Description: Opinionated component library

Created: 2015-04-02 13:46:22.0

Updated: 2018-01-17 05:24:00.0

Pushed: 2018-01-26 14:35:20.0

Homepage: http://metosin.github.io/palikka/palikka.core.html

Size: 138

Language: Clojure

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README

Palikka

API Docs.

Project statement

Unlike more general of our libraries (like compojure-api and ring-swagger) this project is primarily intended for use in Metosin's projects. Feel free to use, but don't expect full support.

• We might remove features if we think they are not useful anymore
• We will reject PRs and issues about features we wouldn't use ourselves

Features

• The components use clojure.tools.logging
• The components use Schema to validate and coerce their configuration
  • Coercion allows using strings from environment variables and system properties easily
• Includes test utilities for clojure.test and Midje.
• Context is curated value created from interesting parts of the system.
  • Passing the whole system down to implementation is inconvenient as the interesting bits of system are somewhere inside the components.
  • Follows the semantics of using
  • (providing (mongo/create (:db env)) [:db]) will publish value of (:db mongo) as (:db context)
  • (providing (mongo/create (:db env)) {:mongo :db}) will publish value of (:db mongo) as (:mongo context)
  • (providing (mongo/create (:db env)) {:mongo (fn [component] (:db component))}) will publish value of (:db mongo) as (:mongo context)
• Ring handler can be created using a function taking system as argument. This makes it easy to create handler accessing system or context, directly or through middleware.
  • (http-kit/create (:http env) {:fn (fn [system] (let [ctx (palikka.core/create-context system)] (fn [req] {:body ctx})))})
• Idempotent components

Differences to System

• Components log messages
• Context
• Schema validation and coercion for options

Example

n base-system [override]
et [env (m/build-config
          (m/resource "config-defaults.edn")
          (m/file "./config-local.edn"))
    create-handler (fn [system]
                     (-> (create-handler system)
                         (wrap-context system)))]
(component/system-map
  :mongo        (-> (mongo/create (:mongo env))
                    (providing {:db :db, :gfs :gfs}))
  :http         (-> (http-kit/create (:http env) {:fn create-handler})
                    ; Though components are accessed through context,
                    ; complete system map is needed for creating the context
                    (using [:mongo]))
  :nrepl        (nrepl/create (:nrepl env)))))

Component dependencies

This library doesn't depend on libraries used by components, depend on these on your project.

• Http-kit: http-kit
• Mongo: monger
• Database: hikari-cp & jdbc driver for used db, e.g. postgres driver
• Migration status checker: flyway-core
• RabbitMQ: Langohr
• Datomic: [com.datomic/datomic-free "0.9.5327"] or Datomic Pro

License

Copyright © 2015-2016 Metosin Oy

Distributed under the Eclipse Public License, the same as Clojure.