but if you did use thermometer in space it would eventual read 2.73 kelvin right? so whats the issue? and also for a space based server it would have to deal with the energy coming from the sun
There is no matter.
It's cold there because there isn't anything there.
So there is nothing to conduct or convect the heat away.
It's like a giant vacuum insulated thermos.
Is putting data centers in thermos' a good idea?
what thermometer would you use to measure the temperature of space?
Yes and no.
If you had a thermometer that had no heat generation then yes.
If you have a resistor or other heat generating circuit then you need to have the needed surface area to radiate the heat away. If you don't, it will heat up. It's a rate problem.