Symphony.

So guys; we've been running a website on Symphony 2.2 for quite a while, recently I made some changes to a 'remote' datasource and the site's been flying since the change. Till when we noticed we had some 500s on some pages [turned out to be encoding]. And we fixed the whole lot.

However at times I'm getting spikes of over 30s in XSLT Generation. I've gone through our Extensions and put a Profiler on each to know how long the delegates take. I've spotted two FrontendOutputPreGenerate and one FrontendOutputPostGenerate and I put a timer before and after each - since these make part of the XSLT Generation when profiling. Below find a list.

Engine Initialisation   0.0000 s
Page creation process started   0.2221 s
XML Built   0.8746 s
XML Generation  0.0037 s
Page Built  1.0150 s
Before PreGen1  0.0009 s
PreGen1 0.0069 s
Before PreGen2  0.0001 s
PreGen2 0.0087 s
Before PostGen  26.1193 s
PostGen 0.2239 s
XSLT Transformation 0.0001 s
Page creation complete  27.5972 s

Note that this behavior is utterly inconsistent and i would get less then 0.8s on one try and something over 30s the next. I'd like to be able to iron out the problem however not sure what I should be looking it.

PS. we have a planned website move / replacement coming up in 2/3 months so having a reply that would mean issue won't come up again; would be something I'd be more then happy to hear :)