[mod_python] Re: Graphs in a webpage

Graham Swallow gps at trix.dircon.co.uk
Wed Nov 15 19:56:52 EST 2000

On Tue, 14 Nov 2000, Alexis Iglauer wrote:

> My datafiles are time series data, usually for 24
> hours at a time, so I will have a whole bunch of
> datafiles which make up a contiguous set of data over
> several days/months/years.

	I have a similar situation, but not in apache_mod.  The data is
	an array of floats (binary portable), one every minute for a week,
	over the year.

	Repackaging last weeks data is slow, but you dont do that for
	every request.

	I use Array to get it as a string, then I use zlib to get a string,
	then I 'escape' the data for MySql (using the standard function)
	and write it into a blob field.

	The data comes back with no need for un-escaping (its so that it
	goes into an SQL statement).

	Then I call a C function to convert the floats to doubles and
	create a BLT/Vector. Its very quick.

	Using GD (or whatever) should not be slow, but a bit of C at the
	right place means you move chunks of data around, not iterate
	python over thousands of items.

	The 'most recent' file obviously needs special treatment.
	You could re-process today every hour (hint: move, start new file,
	then process the moved file, if fail - dont delete).

	That still leaves you with a 'double' data source, first SQL, then
	the additional file.  Alternatively, get the data collector to
	post the data ...


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