Archive for the ‘PyISAPIe’ tag
Using TileCache on IIS
I’ve previously written about using PyISAPie to run Python under IIS – this allows Python scripts to run faster than using CGI. Rather than starting up the Python interpreter each time a request is made to the web server, PyISAPIe starts the interpreter once and only needs to run the script at each request.
TileCache provides a Python-based WMS-C/TMS server – this is allows you create a local disk-based cache of any WMS server (in my case MapServer), and then connect to it through a WMS-C client such as OpenLayers. Using a cache means that rather than have MapServer create an image for every single request for a tile, the first time a tile is requested the image is saved in a folder on the server. On all subsequent requests for the same data TileCache can retrieve this file without needing MapServer. Performance increase is incredible – however watch out for filling up disk space, and remember to empty the cache if you change symbology or update your data.
As mod_python is now officially dead (and has been moved in Apache’s attic), it is yet another reason if you are using Windows servers to run everything through IIS rather than the rather clumsy Apache on Windows. Why pay for Windows, and then install a web server port, thereby losing all the tools, security, and utilities within Windows to manage and administer the web server?
The aim of this post is to describe the set up of TileCache, running through IIS. Read the rest of this entry »
Compiling a 64 bit Version of PyISAPIe
Welcome to a veritable novella. I’ll jump straight to the end – there is no happy outcome, as yet, to this post there is a happy outcome! I have compiled a 64 bit PyISAPIe DLL (a program that runs Python at high speed under IIS), and it is up and running on Windows Server 2008 and IIS7. Many thanks to Phillip Stabon, the creator of PyISAPIe, for additional help, and for the latest version of PyISAPIe which makes compilation for different set ups much easier.
Some background information – I’ve not done any C++ for 10 years (and even then my most advanced program was to finish off a code sample on a hotel register for pirates – of the traditional kind). Also I’ve never used Subversion. Hence there are lots of pictures, and every step is detailed. If there’s anything missing let me know.
I’m not sure why I started doing this – the performance of Python using 32-bit version is fine, and since I started working on this Phillip Stabon, has mentioned he will be making a 64 bit DLL himself. However as there are many different versions of Python around, and different GIS tools rely on different versions it seemed a good idea to document how to do this from scratch.
In this example I’m using Visual Studio 2008, and a number of other tools that are detailed as I go along. I’ve also got the 64 bit compilation tools installed. There are a few notes from Phillip on compiling it for Windows 64-bit in the discussion lists (see quoted text underneath the post). Since this post was first published there is a newer discussion in the forums.
Anyway “How to Compile PyISAPIe for a 64-bit Server in 5 Easy Steps!”…
Read the rest of this entry »
Setting Up Python on IIS7
I had already configured Python to run through the Apache webserver on my development server, but after a few issues on the production server (Apache freezing / crashing) I wanted to test running Python scripts with IIS7. The principle aim was to run TileCache through IIS rather than requiring Apache.
Why Not CGI?
While IIS 7 has Fast-CGI installed (see this IIS forum), even better performance can be achieved using ISAPI. This answer from ServerFault has a good summary on why ISAPI should be preferred over than CGI. Not only performance should be considered – maintenance should also be taken into account. If a web master or hosting service is familiar with IIS then they are also likely to be familiar with ISAPI.
From the PyISAPIe site:
The reason ISAPI applications have the capability of being better than CGI or FastCGI applications is mostly due to its tight integration with the web server environment. Instead of initializing an entire program from scratch (in this case, the Python interpreter) every time a request is made for a page, an ISAPI extension only has to provide a function that is called upon every request. For interpreting Python scripts on a per-request basis, this means that the interpreter can be initialized once and used many times, creating a very noticeable performance gain.