[Swift-devel] log plots of start/end times

[Ben Clifford]

The logs that come out of swift have multiple notions of 'start' and 
'end'.

Two are:

  the karajan job sumission Active time and Completed time

and

 the wrapper log start and end times.

In a perfect world, these would be very close together. In reality they 
aren't. For gram2, they'll likely be way off (by about 30s); in gram4 they 
should be much closer, and I guess in the provisioning providers - falkon 
and coasters - they should be pretty close together.

In interactions with a couple of people in the past month I've had concern 
about lack of correlation (specifically how much can you rely on the first 
above to imply the second?) so I've added a couple of plots to the 
standard swift-lot-log plots that the log-processing module makes. These 
appear at the bottom on the info page on plots.

The first plots the difference between info and karajan start times for a 
job, with the x axis being info start time (to indicate slow-downs in 
state change that are tied to a particular time, as I think some gram4 
notification slowdowns might be); and the second shows two cumulative 
plots for how much difference is between the karajan and info times - in 
local mode, the start line is a little bit above the x=y line and the end 
line is a little bit below x=y. With more interesting job submission 
systems I'd expect these lines to diverge a bit more; in the rumoured case 
of gram4 notifications being quite delayed in some cases, I'd expect some 
linear shift to the left(?).

Mostly these are here in order to get a feel for how appropriate it is to 
regard the karajan start/end times as actual job execution times _ think 
often not, but this is intended to give me the pretty pictures to say yes 
or no.

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