Trapperkeeper-Quick-Start.md

Trapperkeeper Quick Start

Lein Template

A Leiningen template is available that shows a suggested project structure:

lein new trapperkeeper my.namespace/myproject

Once you've created a project from the template, you can run it via the lein alias:

lein tk

Note that the template is not intended to suggest a specific namespace organization; it's just intended to show you how to write a service, a web service, and tests for each.

Hello World

Here's a "hello world" example for getting started with Trapperkeeper.

First, you need to define one or more services:

(ns hello
  (:require [puppetlabs.trapperkeeper.core :refer [defservice]]))

;; A protocol that defines what functions our service will provide
(defprotocol HelloService
  (hello [this])

(defservice hello-service
  HelloService
  ;; dependencies: none for this service
  []
  ;; optional lifecycle functions that we can implement if we choose
  (init [this context]
      (println "Hello service initializing!")
      context)
  ;; implement our protocol functions
  (hello [this] (println "Hello there!")))

(defservice hello-consumer-service
  ;; no protocol required since this service doesn't export any functions.
  ;; express a dependency on the `hello` function from the `HelloService`.
  [[:HelloService hello]]
  (init [this context]
    (println "Hello consumer initializing; hello service says:")
    ;; call the function from the `hello-service`!
    (hello)
    context))

Then, you need to define a Trapperkeeper bootstrap configuration file, which simply lists the services that you want to load at startup. This file should be named bootstrap.cfg and should be located at the root of your classpath (a good spot for it would be in your resources directory).

hello/hello-consumer-service
hello/hello-service

Lastly, set Trapperkeeper to be your :main in your Leiningen project file:

:main puppetlabs.trapperkeeper.main

And now you should be able to run the app via lein run --config .... This example doesn't do much; for a more interesting example that shows how you can use Trapperkeeper to create a web application, check out the Example Web Service included in the Trapperkeeper webserver service project. To get started defining your own services in Trapperkeeper, head to the Defining Services page.