What applications benefit from HAppS?
HTTP requests and SMTP envelopes encapsulate transactions and not vice
versa.
Note: doing otherwise with LAMP is considered bad design because it
implies a requirement to maintain and garbage collect database
connections arbitrarily. So this should not be a high hurdle.
All operating data fits in memory (store blobs on disk.)
Note: Although this seems like a high hurdle, COTS servers with 12gb of
memory are readily accessible and some vendors let you reach up to
500gb of RAM. FYI, eBay has around 50M active users. If you maintained
1k of queryable data for each of their users, you would need only 50GB.
(You would also need to recompile your app for 64bits so the math is a
little more involved but you get my point).
You don't need more CPU power to server your app than you can obtain in
a single machine.
Note: I have not benchmarked this code yet, but another Haskell server
was benchmarked at near 1000 HTTP transactions per second on a Pentium
4 in 2000. Modern web servers with similar architecture can serve 10k
HTTP transactions per second. eBay serves 400M page views per day,
which comes to an average load of 5000 hps and a peak load of perhaps
50k hps. In other words, an OTS 8 CPUs system, could handle all of
eBay's HTTP traffic.
I am not saying that using HAppS, you could serve all of eBay on a
single box. I am saying that your application is likely to be well
within the constraints required for HAppS to make sense for it.
