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 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.
