October 03, 2015

Recipe for using sqitch on Codeship

The sqitch tool is a standaone database migration tool not tied to any language. It doesn’t try and sync models with your database, or assume that it should be managing everything in your database, or generally stick its fingers where they don’t belong.

David Wheeler (the author) has put a ton of work into making installation straightforward, as evidenced by the substantial list of installation alternatives (cpan and cpanm, apt-get, homebrew, yum) on the homepage.

However the linux-based ones assume you’ve got sudo rights, and that’s not true on CI services like Codeship. Here are the steps I went through to make sqitch available for my tests:

1. Test settings

Most of the work is done here.

The first step is to download and install cpanminus because the default cpan isn’t as amenable to one-time automated use. 1

pushd ~/bin
curl -L https://cpanmin.us/ -o cpanm
chmod +x cpanm

Yes, this is downloading a script directly from the internet. It’s one that’s auto-generated from the module’s source, and the author is very well known and regarded. If we were paranoid we could download the script ourselves and put it on a server we control.

Next we need to install sqitch. We’re using Postgres so in addition to installing the module itself we’re installing the Perl-to-Postgres database interface:

~/bin/cpanm --notest App::Sqitch DBI DBD::Pg

Finally we need to modify the path and tell Perl where these additional libraries are stored. The output of the above step starts with this banner:

! Can't write to /usr/local/share/perl/5.18.2 and /usr/local/bin: Installing modules to /home/rof/perl5
! To turn off this warning, you have to do one of the following:
!   - run me as a root or with --sudo option (to install to /usr/local/share/perl/5.18.2 and /usr/local/bin)
!   - Configure local::lib your existing local::lib in this shell to set PERL_MM_OPT etc.
!   - Install local::lib by running the following commands
!         cpanm --local-lib=~/perl5 local::lib && eval $(perl -I ~/perl5/lib/perl5/ -Mlocal::lib)

The very end of that first line tells us the path where our modules will be installed. (It’s Codeship-specific, but AFAIK it’s stable from project-to-project.) We’ll need to include that in the path and library setting. With those environment variables here’s what the full test settings look like (in an easy copy-paste block):

# install cpanminus
mkdir -p ~/bin
pushd ~/bin
curl -L https://cpanmin.us/ -o cpanm
chmod +x cpanm

# install sqitch and postgres interface
~/bin/cpanm --notest App::Sqitch DBI DBD::Pg

# make sqitch and libraries available
export PATH=/home/rof/perl5/bin:$PATH
export PERL5LIB=/home/rof/perl5/lib/perl5

2. Your test script

We have a standard test.sh script at the root of every project. It doesn’t do a whole lot, but it gives us a place to put CI-specific configuration. In the Codeship case the only thing we need to change is the port. 2 Since we’re using 9.4-specific features we set it to 5434. Here’s the setup we do to create a database and deploy migrations with sqitch:



if [ "$CI" = "true" ]; then
DB_COUNT=`psql --port $PORT -l | grep -c "$DATABASE_NAME "`
if [ $DB_COUNT -eq 0 ]; then
  echo "Database does not exist, creating..."
  psql --port $PORT -c "CREATE DATABASE $DATABASE_NAME" postgres

sqitch deploy db:pg://localhost:$PORT/$DATABASE_NAME
if [ $? -ne 0 ]; then
  echo "Sqitch migration FAILED. Refusing to run tests."
  echo "Dropping database for clean next run."
  psql --port $PORT -c "DROP DATABASE $DATABASE_NAME" postgres
  exit 1
echo "Database setup done. Run tests..."

3. Profit!

A successful test output now starts with something like this (individual migration names depend on your project, of course):

Database does not exist, creating...
Adding registry tables to db:pg://localhost:5434/myproject_test
Deploying changes to db:pg://localhost:5434/myproject_test
+ ltree ........ ok
+ groups ....... ok
+ memberships .. ok
+ activities ... ok
Database setup done. Run tests...

Go forth and migrate!

  1. There are many tips -- like this one from SO -- on generating an automation-friendly config for CPAN, but they seem to be geared toward making tasks automatable for convenience rather than necessity.
  2. Codeship runs different versions of Postgres on different ports, which is a pretty elegant solution IMO.
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