Recently I've come face-to-face with a significant processing task for a web application written in PHP.  I haven't worked with process control very much, so I started researching ways of distributing the calculations to multiple processes.  PHP offers several libraries for doing this (pcntl, POSIX), but it quickly became clear that if you're running Windows these libraries are not an option, and unfortunately at work I have a Windows machine.  After a lot more research, I came across Gearman.

Gearman is essentially a distributed processing framework, and seems to have community support for many programming languages.  It consists of two main components: the job server, and a Client and Worker API.  The Client and Worker API can be used in a wide variety of languages, but the job server is only available as a C library or a Perl library.  This makes it a bit tougher to get the server running on Windows, especially when you start running into some of the dependencies that it requires to build.  As well, the Client/Worker API for PHP can only be installed as a PECL extension, or a very-out-of-date PEAR extension called Net_Gearman.

Nonetheless, after yet more research I decided that I would give it a shot by using Cygwin to get the job server running (if you haven't used Cygwin before, be sure to read about it before attempting to install Gearman this way), and PEAR to use the API.  Pre-built PECL extensions aren't available for Windows anymore, and the build process for PHP extensions can be pretty painful, so it makes PEAR look good by comparison even if the code will be out of date.

I had a pretty frustrating time finally getting everything up and running due to various dependency issues, so I went back through the whole process and wrote it out step-by-step.  I used a Windows XP SP3 machine for this, but I also got it working on a Windows 7 machine as well.

Installing the Gearman job server (gearmand) on Windows with Cygwin

Installing Cygwin

1. If you don't have Cygwin already, you can get it from http://www.cygwin.com.  The setup file is located here, and the setup process is pretty straightforward; run it and follow the wizard.  Full installation instructions are available at the Cygwin site.
2. Keep the Cygwin setup.exe file handy after you've installed the default software packages, as you'll need it in the future to add packages, similar to apt-get, yum, and other Linux/UNIX package managers.
3. Cygwin installs with some basic packages, including a Cygwin Bash Shell that goes into your Start Menu.  I prefer the mintty emulator instead, as it has less of a DOS Command Prompt feel and better terminal features.  Feel free to use whatever shell you like of course.  You can get mintty by re-running the setup.exe, and at the package selection screen, type 'mintty' into the Search bar at the top left.  Expand the "Shells" category, and click on the word "Skip" under the "New" column beside the mintty package to select it before continuing the install process.

Installing Cygwin Package Dependencies needed for Gearman

If you're not already in the Cygwin setup, re-run the Cygwin setup.exe and go through to the package selection screen.  The following is a list of dependency packages you will need in order to build the Gearman job server (gearmand).  None of these packages were installed by default with Cygwin:

• gcc
• make
• libuuid1-devel
• libiconv

There's a good installation tutorial here that walks through getting gcc and make installed for people unfamiliar with Cygwin.  Finding the others is pretty straightforward, the Search bar in the package selector works well.

Installing libevent

Gearmand requires an event notification library called libevent that you cannot get as a Cygwin package, which means it has to be installed from source.  You can get the source here.

1. Download and unpack the latest libevent stable release.  At the time of this writing, I used libevent-1.4.14b-stable.
   NOTE: Download and unpack to a directory that does not contain spaces in the name, such as "C:/cygwin/home/Zombat/libevent-1.4.14b-stable".  If you unpack to something with spaces like "C:/Documents and Settings/Zombat/", the build process might not be able to install libevent correctly (libtool has a hard time with spaces)!
2. Open a Cygwin shell and cd to the unpacked libevent directory.
3. Run the following commands:

./configure
make
make install

libevent should now be installed and ready to be used when compiling the Gearman job server.

Installing the Gearman job server, gearmand.exe

1. Download and unpack the C implementation of gearmand from http://gearman.org/index.php?id=download
2. Open a cygwin shell and cd to your unpacked gearmand directory.  Same rules apply as before, make sure you've unpacked in a directory with no spaces in the path!  libtool hates that, and your build may fail.
3. Run the following commands:

./configure
make
make install

The Gearman job server should now be installed and ready to use!  Mine was installed at /usr/local/sbin/gearmand.exe, and running it with a "triple verbose" flag (-vvv) should produce the following:

That's it for the job server.  When you want to start it, simply open a Cygwin shell and run gearmand.exe.  Running it with the -d flag will cause the server to run as a daemon in the background, and running with --help will show you the full option list.

Installing the Gearman Client and Worker API (Net_Gearman)

I chose to install the PEAR Client and Worker API, as it is native PHP and doesn't involve compiling PECL extensions.  The PEAR package is called Net_Gearman, and was originally written by Joe Stump at Digg.com.  It is old and out of date now, although there appears to be a more recent fork at http://github.com/brianlmoon/net_gearman.  I stuck with the older version, as I suspect it will meet my needs, and was readily available as a PEAR package.

This also makes installation relatively painless.  Assuming you've previously set PEAR up, then all you have to do is open a command window (not a Cygwin shell) and run:

pear install Net_Gearman-alpha

The "-alpha" portion is necessary, as Net_Gearman apparently never made it to a stable release version.  That being said, it has functioned well for me so far.  Perhaps someone will pick the project up in the future.

I'll write more about getting started with the Client and Worker API in the next article, so we can actually use Gearman to get some work done.