Hi all, I'm currently working on a project where we have a need to expose an Excel spreadsheet on the web as a webservice that needs to be reliable and available 24x7x365. I've implemented a prototype of this in python using the win32com library to interface with the Excel Automation API via COM. I've also used web.py as a way to expose this automation functionality to the network. This works just fine as a prototype that proves that it is possible to do something like this.
I'm not revisiting the code with the goal of making it more reliable and available, able to support multiple users (although only allowing one at a time to use Excel). This means that Excel is going to potentially be used from multiple threads -- something I know that has historically caused problems for a lot of people based on my searches of the newsgroup. What I'd like to know is what is the proper strategy that I should be taking here? I see several options: 1) Ignore threads entirely. Let every incoming web thread interface directly with excel (one web thread at a time -- I'll have an interpreter scoped lock preventing multiple threads from accessing). 2) Dedicate a single worker thread to do all interaction with Excel. Pass data off to this thread from the incoming web thread via shared memory and let the worker thread get Excel to process it. This will ensure that exactly 1 thread ever interacts with Excel. 3) Spawn a new interpreter (literally spawn another python process) for each incoming web thread. This will ensure that when a process is finished with Excel there is no chance of any lingering state or something improperly cleaned up. I've actually attempted to implement 1) and 2) and have had problems with sporadic failures that cause the Excel to no longer be accessible from the interpreter. I've tried very hard to ensure that pythoncom._GetInterfaceCount() always returns 0 when I believe I'm finished with excel. I don't think I'm perfect at always getting a 0, but I'm pretty close. I believe that some of my problems are caused by not being perfect about this but haven't been able to track down the leaking references. I'm definitely not an expert in COM or its threading models. What techniques does the group suggest? Is spawning a new interpreter for every request a bit too extreme (I don't mind the performance hit). Has anyone ever done anything like this? How did you get around these problems? Thanks, Brandon -- http://mail.python.org/mailman/listinfo/python-list
