PHP Sessions in Erlang Mnesia

Motivation

  • create a very simple first Erlang/OTP application
  • link to conventional web development

I decided one of the simplest things to do would be to create a session storage for PHP in Mnesia. But that, in doing so, I would also create an extremely simple key value store wrapper around Mnesia which would track access times.

Disclaimer

Do NOT use this in production, or anywhere where it’s important. If you do, you’re crazy because:

  • it has not been tested in production or production-like environment
  • as I mentioned, this is my first Erlang application
  • connection is made to a single Erlang node, and there is no failover mechanism if that fails
  • session garbage collection is not implemented

Good Stuff

OK, the disclaimer is out of the way, let’s get to the good stuff! Here’s what I did and how.

Tools used

  • Erlang runtime and development headers
  • PHP >=5.3 (>=5.4 preferred) binary and development headers
  • Apache
  • mypeb
  • kvstore
  • lib360

Architecture

[ PHP ] <–> [ mypeb ] <–> [ Erlang ] <–> [ kvstore ] <–> [ Mnesia ]

Instructions

  • download and install prerequisites as best done in your environment
    • Erlang runtime and development headers
    • Apache
    • PHP >=5.3 binary and development headers
  • download and compile mypeb
    • git clone git://github.com/videlalvaro/mypeb.git
    • cd mypeb
    • phpize
    • ./configure
    • make
    • sudo make install
    • php -m | grep peb
    • Note 1: the last command is a test to verify peb module loads successfully
    • Note 2: you might need to specify --with-erllib and --with-erlinc options with ./configure command if they are not automatically found
  • download, compile and run kvstore
  • download lib360
    • git clone git@github.com:unix1/spoof.git
  • add sample PHP script to your web server and test everything
    • download sample gist
    • replace the path in require_once() to wherever you downloaded lib360
    • replace the your-erlang-cookie-here with the contents of ~/.erlang.cookie file
    • access the file through the web server and have fun!

Missing

These are things that I thought of but didn’t bother implementing that I might someday add:

  • make kvstore more configurable and easy to install/start/stop
    • kvstore currently fails to stop (you have to abort)
    • it could use rebar and more automated scripts instead of manual commands
    • support for configurable multiple table names
    • make access time tracking optional
    • implement other storage backends
  • account for failover when primary node connection fails from PHP
  • PHP session garbage collection
  • implement kvstore access through lib360 database layer

Suggestions/Contributions/Feedback

If you have any feedback, feel free to give it via github, blog comments, etc. as appropriate. Enjoy!

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