django-pgrunner 0.2.2

Create and autorun a PostgreSQL development database for your Django project

Django-pgrunner creates a local PostgreSQL database for your project and automatically starts the database server when needed. It allows you to develop against a PostgreSQL server, while matching the convenience of a SQLite3 database file.

The local database is a self-contained database created using the PostgreSQL initdb tool. A separate PostgreSQL server will be started on a custom port.

Additionally, it support creating and activating database snapshots. This allows you to experiment with your data and be confident that you can restore your old data within seconds.

Why?

While sqlite3 is great for development, being able to develop against a full-featured database like PostgreSQL has a few huge benefits:

• Your development database will match the database you run in production, eliminating a whole category of bugs, like:

  • South migrations failing in production, while working in dev

  • Errors in code due to database specific behaviour, like stricter checks on foreign key references.

  • Proper checks on unique_together (sqlite3 does not support these constraints)

• You can use all the great features offered by PostgreSQL, instead of restricting yourself to a low common denominator. Examples:

  • Database-side constraint and cascading rules

  • Extra data types, like arrays

  • Full-text search

  • Views

  • Stored procedures

  • Triggers

  • PostGIS geo extensions

  • HStore

  • JSON features

And with the ease of use this packae offers, there is no good reason not to use it!

Requirements and installation

Make sure you have PostgreSQL installed. You can either compile from source, or install a binary for your operating system. Check the download page for details. For MacOS X users, I recommend downloading PostgresApp.

The snapshot functionality requires rsync to be installed.

This package depends on the psycopg2 package. psycopg2 provides the Python database adapter needed to communicate with PostgreSQL. This adapter is partly written in C, and requires a working C compiler, PostgreSQL development headers and the pg_config binary in your PATH. Alternatively, you can install a binary distribution.

pip install psycopg2

The easiest way to install django-pgrunner is using pip:

pip install django-pgrunner

Microsoft Windows is currently not supported.

This package is not intended for use on production servers.

Usage

First, add pgrunner to your INSTALLED_APPS.

Next, add the following lines to your settings.py or local settings file. Make sure that these come after any DATABASES setting:

# If your PostgreSQL binaries are not in your path, add this setting
#PGRUNNER_BIN = '/usr/lib/postgresql/9.3/bin'
#PGRUNNER_BIN = '/Applications/Postgres.app/Contents/Versions/9.3/bin'

# This will overwrite DATABASES and auto-start PostgreSQL if needed
import pgrunner
pgrunner.settings(locals())

Note that most Linux distibutions do not include these binaries in the PATH, and only expose a few wrappers in /usr/bin. If this is the case for you, you need to set the PGRUNNER_BIN setting.

Run the following command to create your local database:

./manage.py pg_init

To start the database in the background:

./manage.py pg_ctl start

Note that if you use pgrunner.setting(), it will automatically start the server for you.

To stop the database:

./manage.py pg_ctl stop

This will not be done automatically.

To start the psql command line interface with the right parameters, use one of these commands:

./manage.py dbshell
./manage.py pg_psql

The only difference is that the first one uses your DATABASES settings, and the second one ignores it.

Snapshots

Snapshots are nothing more than named copies of the full database. It’s the equivalent of a cp dev.sqlite my-backup.sqlite for SQLite users.

To create a snapshot and activate it:

./manage.py pg_snapshot my-snapshot
./manage.py pg_activate my-snapshot

The name of the default snapshot you are running is default, so to switch back:

./manage.py pg_activate default

Snapshots can be deleted by removing their folder under pgrunnerdb/.

Command summary

./manage.py pg_init          - Initialize a local database environment
./manage.py pg_ctl start     - Start server in background
./manage.py pg_ctl stop      - Stop server in background
./manage.py pg_ctl status    - Check if the server is running
./manage.py pg_run           - Run PostgreSQL server in foreground
./manage.py pg_psql          - Start psql with right parameters
./manage.py pg_snapshot foo  - Create a copy of all current database data
./manage.py pg_activate      - List all snapshots
./manage.py pg_activate foo  - Activate snapshot 'foo'
./manage.py pg_dump          - Run pg_dump
./manage.py pg_restore       - Run pg_restore

Behind the scenes

Django-pgrunner creates a pgrunnerdb/ subfolder under your Django project. This folder contains one folder for every snapshot that was created. The name of the default instance is default. A current symbolic link keeps track of which snapshot is active.

A separate PostgreSQL daemon is started for every project. When the pg_init management command is run, it will pick a random port between 15000 and 16000 to run the server on and write it to the local postgres.conf. This way the chances of a conflict between projects are small.