Sat, 30 Apr 2016

Automating Deployments: Stage 2: Uploading

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Once you have the pipeline for building a package, it's time to distribute the freshly built package to the machines where it's going to be installed on.

I've previously explained the nuts and bolts of getting a Debian package into a repository managed by aptly so it's time to automate that.

Some Assumptions

We are going to need a separate repository for each environment we want to deploy to (or maybe group of environments; it might be OK and even desirable to share a repository between various testing environments that can be used in parallel, for example for security, performance and functional testing).

At some point in the future, when a new version of the operating system is released, we'll also need to build packages for another major version, so for example for Debian stretch instead of jessie. So it's best to plan for that case. Based on these assumptions, the path to each repository will be $HOME/aptly/$environment/$distribution.

For the sake of simplicity, I'm going to assume a single host on which both testing and production repositories will be hosted on from separate directories. If you need those repos on separate servers, it's easy to reverse that decision (or make a different one in the first place).

To easy the transportation and management of the repository, a GoCD agent should be running on the repo server. It can copy the packages from the GoCD server's artifact repository with built-in commands.

Scripting the Repository Management

It would be possible to manually initialize each repository, and only automate the process of adding a package. But since it's not hard to do, taking the opposite route of creating automatically on the fly is more reliable. The next time you need a new environment or need to support a new distribution you will benefit from this decision.

So here is a small Perl program that, given an environment, distribution and a package file name, creates the aptly repo if it doesn't exist yet, writes the config file for the repo, and adds the package.

use strict;
use warnings;
use 5.014;
use JSON qw(encode_json);
use File::Path qw(mkpath);
use autodie;

unless ( @ARGV == 3) {
    die "Usage: $0 <environment> <distribution> <.deb file>\n";
my ( $env, $distribution, $package ) = @ARGV;

my $base_path   = "$ENV{HOME}/aptly";
my $repo_path   = "$base_path/$env/$distribution";
my $config_file = "$base_path/$env-$distribution.conf";
my @aptly_cmd   = ("aptly", "-config=$config_file");


sub init_config {
    mkpath $base_path;
    open my $CONF, '>:encoding(UTF-8)', $config_file;
    say $CONF encode_json( {
    rootDir => $repo_path,
    architectures => [qw( i386 amd64 all )],
    close $CONF;

sub init_repo {
    return if -d "$repo_path/db";
    mkpath $repo_path;
    system @aptly_cmd, "repo", "create", "-distribution=$distribution", "myrepo";
    system @aptly_cmd, "publish", "repo", "myrepo";

sub add_package {
    system @aptly_cmd,  "repo", "add", "myrepo", $package;
    system @aptly_cmd,  "publish", "update", $distribution;

As always, I've developed and tested this script interactively, and only started to plug it into the automated pipeline once I was confident that it did what I wanted.

And as all software, it's meant to be under version control, so it's now part of the deployment-utils git repo.

More Preparations: GPG Key

Before GoCD can upload the debian packages into a repository, the go agent needs to have a GPG key that's not protected by a password. You can either log into the go system user account and create it there with gpg --gen-key, or copy an existing .gnupg directory over to ~go (don't forget to adjust the ownership of the directory and the files in there).

Integrating the Upload into the Pipeline

The first stage of the pipeline builds the Debian package, and records the resulting file as an artifact. The upload step needs to retrieve this artifact with a fetchartifact task. This is the config for the second stage, to be inserted directly after the first one:

  <stage name="upload-testing">
      <job name="upload-testing">
          <fetchartifact pipeline="" stage="build" job="build-deb" srcdir="package-info">
            <runif status="passed" />
          <exec command="/bin/bash">
            <arg>deployment-utils/add-package testing jessie package-info_*.deb</arg>

Note that testing here refers to the name of the environment (which you can chose freely, as long as you are consistent), not the testing distribution of the Debian project.

There is a aptly resource, which you must assign to the agent running on the repo server. If you want separate servers for testing and production repositories, you'd come up with a more specific resource name here (for example `aptly-testing^) and a separate one for the production repository.

Make the Repository Available through HTTP

To make the repository reachable from other servers, it needs to be exposed to the network. The most convenient way is over HTTP. Since only static files need to be served (and a directory index), pretty much any web server will do.

An example config for lighttpd:

dir-listing.encoding = "utf-8"
server.dir-listing   = "enable"
alias.url = ( 
    "/debian/testing/jessie/"    => "/var/go/aptly/testing/jessie/public/",
    "/debian/production/jessie/" => "/var/go/aptly/production/jessie/public/",
    # more repos here

And for the Apache HTTP server, once you've configured a virtual host:

Options +Indexes
Alias /debian/testing/jessie/     /var/go/aptly/testing/jessie/public/
Alias /debian/production/jessie/  /var/go/aptly/production/jessie/public/
# more repos here

Achievement Unlocked: Automatic Build and Distribution

With theses steps done, there is automatic building and upload of packages in place. Since client machines can pull from that repository at will, we can tick off the distribution of packages to the client machines.

I'm writing a book on automating deployments. If this topic interests you, please sign up for the Automating Deployments newsletter. It will keep you informed about automating and continuous deployments. It also helps me to gauge interest in this project, and your feedback can shape the course it takes.

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