Question

I am running a classic vbscript ASP site with a SQL2008 database. There are a few pages that are processor-heavy, but don’t actually change that often. Ideally, I would like the server to process these once a night, perhaps into HTML pages, that can then fly off the server, rather than having to be processed for each user.

Any ideas how I can make this happen?

The application itself works very well, so I am not keen to rewrite the whole thing in another scripting language, even if classic asp is a bit over the hill!!

Answer 1

Yes :

You didn’t specify which parts of the pages are “processor heavy” but I will assume it’s the query and processing of the SQL data. One idea is to retrieve the data and store it as a cached file, in the filesystem. XML is a good choice for the data format.

Whereas your original code is something like this:

 (psuedocode)
 get results from database
 process results to generate html file

…your modified code can look like this:

check if cache file exists
if not exist
   get results from database
   store results in cache file
get results from cache file
process results to generate html file. 

This is a general caching approach and can be applied to a situation where you’ve got
query parameters determining the output. Simply generate the name of the cache file based on all the constituent parameters. So if the results depend on query parameters named p1 and p2, then when p1 and p2 have the values 1234 and blue respectively, the cache file might be named cache-1234-blue.xml . If you have 5 distinct queries, you can cache them as query1-1234-blue.xml, query2-1234-blue.xml and so on.

You need not do this “nightly”. You can include in your code a cache lifetime, and in place of the “if cache file exists” test, use “if cache file exists and is fresh”. To do that just get the last modified timestamp on the cache file, and see if it is older than your cache lifetime.

Function FileOlderThan(fname, age)
    'function returns True if the file is older than the age,
    '  specified in minutes.
    Dim LastModified, FSO, DateDifference

    Set FSO = CreateObject("Scripting.FileSystemObject")
    LastModified = FSO.GetFile(fname).DateLastModified
    DateDifference = DateDiff("n", LastModified, Now())
    If DateDifference > age Then
        FileAge = False
    Else
        FileAge = True
    End If
End Function


fname = Server.MapPath(".") & cacheFileName
If FileOlderThan(fname, 10) Then
   ... retrieve fresh data ...
End If 

This could be 10 minutes, 10 hours, 10 requests, whatever you like.

I said above that XML is a good choice for the data format in the cachefile. ADO has a SaveAsXML method, and you can also generate XML directly from SQL2008 using the FOR XML clause appended to the query.

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If the “processor heavy” part is not the query and retrieval, but is the generation of the html page, then you could apply the same sort of approach, but simply cache the html file directly.