Mimi Yin wrote:
<Jared, please scroll down to see a question for you.>
(Whoah, I thought I sent this out earlier, but I just found it in my
drafts folder; sorry for the delay in response.)
Again, I think we need some numbers for Preview. How many simultaneous
requests do we expect in the Preview timeframe? Jared?
We're expecting about 40 transactional requests per second at maximum
capacity. But by itself, that metrics is pretty meaningless; the
relevant issue is the complexity of each request times the frequency of
those request.
The most expensive operations we have right now are "webcal GET", say
for iCal and Google Calendar users (roughly 6 seconds each on a loaded
server), and "Atom/RSS GET" (for feeds) but the kicker is those happen
frequently (every 15 minutes for iCal, unknown for Google Calendar). We
could easily find after Preview that these operations dominate the server.
I get nervous if an operation (or sequence of operations) takes more
than say 750-1500 ms (0.75-1.5 sec) and happens more than say 10 times
per person per day. Too many of these expensive operations load the
server and make the web UI slow because the server itself is slow.
I hear performance discussed in this thread, but it's critically
important (to me), to realize that "performance" is shared. It's very
possible, given our centralized server architecture, for one user doing
an expensive operation to affect thousands of users just going about
their daily business.
Since we consciously decided to defer our server-side ability to scale
(that is, add resources to add capacity) in the interests of supporting
more features by Preview, feature decisions must be made so that they
are lightweight against our centralized server.
A good solution, from a service perspective, will make a relatively few
number of HTTP requests, and each will be pretty fast to complete.
Operations that take "seconds" to complete will be a sign of there being
an unacceptable performance problem.
-- Jared
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