Jeff: that does sound pretty awful. Is this issue limited to Python, or have you seen similar results with Java instances?
On Wednesday, July 11, 2012 8:10:14 PM UTC-4, Jeff Schnitzer wrote: > I've been doing some load testing on Python27 frontends and backends > and getting some fairly awful results. > > My test is a simple no-op that returns a 4-letter constant string. I > hit frontend (F1) and backend (B1) versions with ab -c 100. > > The frontend peaks at about 140 requests/sec per instance. I've set > the min latency to 15s to keep the # of instances to a minimum, which > seems to work. It never goes above 2 instances and one of them makes > the 140 mark. The admin instances page shows avg latency of 10-15ms. > However, app logs show varying latency #s ranging from 30ms to 250ms. > > The backend (single instance) peaks under 80 requests/sec. The > admin/instances page shows avg latency of 100ms. App logs show > latencies of 3000-4000ms. > > Questions and observations: > > 1) What does the avg latency # on admin/instances mean? Presumably > this is time spent executing my code and not time spent in the pending > queue. Except that no-ops don't take 100ms to execute. What else is > part of that number? > > 2) Request time in the app logs includes time spent waiting in the > pending queue, right? It's the actual wall-clock time between when > the request enters Google and leaves Google? > > 3) Why are backends so abysmally slow? If a backend is supposed to be > *at all* useful for maintaining in-memory game state for more than > five players, it needs to be able to process a high QPS rate. That's > fine, a couple synchronized operations on an in-memory data structure > are lightning fast - a couple ms. But where does this mysterious > 100ms come from? It destroys throughput. > > 4) Try this exercise: Deploy a frontend handler that does nothing but > urlfetch to a backend no-op. Run it. It usually takes *hundreds* of > milliseconds. I've verified this with appstats. Huh? I can make > urlfetches to Europe faster. > > Jeff -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-appengine/-/bvaCIDFy0IcJ. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
