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Professional Clojure

Sat Apr 27, 2019

So I'm going to be working with Clojure for a bit. Like, at work. And as a result I've had to deal with some minor infrastructure issues I thought I'd share.

S3 Wagon

Setting up a private repository for Clojure libraries is really straightforward. Usually, when I'm working on something, I'll toss it up onto Clojars, but this time, I don't want these repos to be fully public. They're pieces of internal infrastructure that deal with how our deploys are going to work, and possibly reveal some internals that we'd rather keep proprietary for the moment. The alternative I settled on was using s3-wagon-private to host a bunch of library jars on a private bucket. This effectively lets you run your own maven repository.

There are only a couple fiddly bits. The step-by-step guide does a pretty good job of getting you through it.

There are two bits to the workflow that I'd want to automate, or at least semi-automate.

Firstly, every time I edit one of these libraries, I'll want to be able to push it up to our local repository with a minimum of fuss. Secondly, any new project I start for work will need to be able to pull things from those repos.

Pushing

The first bit is reasonably simple; I'll want a shell script that just does the thing. That's fairly straightforward; it looks like

#! /bin/sh

BUCKET="org.your-org-name.clj"
PATH="org/your-org-name/clj"

VERSION=`head -n 1 project.clj | grep -E -o '[0-9]+\.[0-9]+\.[0-9]+'`
PROJECT=`head -n 1 project.clj | grep -oP ' \K([^ "]+)'`

echo "Building uberjar..."
lein uberjar
echo "Deploying locally..."
eval "mvn deploy:deploy-file -Dfile=target/$PROJECT-$VERSION-SNAPSHOT.jar -DartifactId=$PROJECT -Dversion=$VERSION -DgroupId=$BUCKET -Dpackaging=jar -Durl=file:maven_repository -Dmaven.repo.local=maven_repository -DcreateChecksum"
echo "Copying to S3..."
eval "aws s3 cp maven_repository/$PATH/$PROJECT/$VERSION s3://$BUCKET/releases/$PATH/$PROJECT/$VERSION --recursive"
rm -r maven_repository
echo "Done"

This can actually just be a global script. So you might add it as a function to your shell rc file, or you might keep it somewhere on your $PATH and just execute it once. Assuming you have your AWS credentials set, and maven and lein installed, running this in a project directorythis will

  1. Build the project
  2. Deploy to a temporary local maven repository
  3. Copy that subtree up to your S3 bucket
  4. Clean up the temporary local repository

There. Done.

Pulling

The other part is slightly more annoying, because it involves adding stuff to every lein project you create that uses your private repo. You need to remember to add

  :plugins [[s3-wagon-private "1.1.2"]]
  :repositories {"private-repo"
                 {:url "s3p://org.your-org-name.clj/releases/"
                  :username :env/aws_access_key_id
                  :passphrase :env/aws_secret_access_key}}

to your new repos. Forgetting to add the repositories value is pretty easy to diagnose, but forgetting to add that plugins line gives you comparably cryptic messages about required projects not being found in the main maven/clojars registries. Oh, in addition to the above, you probably also want to add the entries for any core libraries your projects use up in the dependencies section, and show require examples over in core.clj.

All of this tells me that what I really want is a new project template.

Creating one starts with adding {:user {:plugins [[lein-create-template "0.2.0"]]}} to your ~/.lein/profiles.clj, then running lein create-template your-org-name1. This should create a project skeleton tree. The only relevant bits for me were actually your-org-name/leiningen/new/your-org-name.clj, and some bits of the your-org-name/leiningen/new/your-org-name/ directory.

The first started as

(ns leiningen.new.your-org-name
  (:use [leiningen.new.templates :only [renderer name-to-path sanitize-ns ->files]]))

(def render (renderer "your-org-name"))

(defn your-org-name
  [name]
  (let [data {:name name
              :ns-name (sanitize-ns name)
              :sanitized (name-to-path name)}]
    (->files data
             ["test/{{sanitized}}/core_test.clj" (render "test/source/core_test.clj" data)]
             ["src/{{sanitized}}/core.clj" (render "src/source/core.clj" data)]
             ["project.clj" (render "project.clj" data)])))

I had to add the lines


             ["mvn-deploy" (render "mvn-deploy" data)]
             [".gitignore" (render ".gitignore" data)]

into that ->files data block. mvn-deploy is the script I showed you above, and the .gitignore is just something for ease of use.

The your-org-name/leiningen/new/your-org-name/ directory contains a project.clj file that needs some surgery too. It defaults to

(defproject {{ns-name}} "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :dependencies [[org.clojure/clojure "1.8.0"]])

and in my case needed to get tweaked over into

(defproject {{ns-name}} "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "proprietary"}
  :dependencies [[org.clojure/clojure "1.8.0"]
                 [org.clojure/tools.cli "0.3.5"]

                 <some-additional-internal-libraries-can-go-here>]
  :plugins [[s3-wagon-private "1.1.2"]]
  :repositories {"local" {:url "s3p://org.your-org-name.clj/releases/"
                          :username :env/aws_access_key_id
                          :passphrase :env/aws_secret_access_key}}

  :main {{ns-name}}.core
  :aot [{{ns-name}}.core])

The Workflow

Once all the tweaks were done, I ran lein install in the your-org-name project directory to get that as an additional template option. At that point, the workflow for a new project becomes

  1. lein new your-org-name new-repo-name
  2. Make some changes to new-repo-name
  3. mvn-deploy
  4. Optionally, tweak your-org-name project to add this to the default internal libraries location in project.clj

There. That should help me write a fuckton more working, installable Clojure code at work. And I feel like this is a noble goal.

As always, I'll let you know how it goes.

  1. As a note here; I actually still had to run the lein create-template command inside of an existing project, then move the resulting folder up to the level of my ~/projects directory. lein complained about the lack of a project.clj file otherwise.


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