App Engine High CPU Warning - Is it really an issue?

I recently finished my app and have since began testing. One of my main resources makes 14 RPCs, I have made every effort to decrease CPU time, i.e., marking properties as unindexed, however 开发者_开发百科I really cannot reduce the number of GETs, PUTs and queries that occur in the request.

The average CPU times associated with the request today is:

ms=381 cpu_ms=1192 api_cpu_ms=1122 cpm_usd=0.033597

This does fluctuate and can be less, however it rarely falls low enough to have the high CPU warnings removed.

I've noticed my app still scales fine, I have about 15 instances running whilst testing.

So my question is, should I be concerned at the high CPU warnings or is it something most people experience?

As long as your wallclock time (the first time in those timings) averages less than 1000ms, your app will continue to autoscale just fine, regardless of how many CPU ms your app uses. As systempuntoout explains, the high CPU warnings are a holdover from when we limited high CPU requests on a per-url basis, and no longer apply except as a guide for optimisation.

If your application can't be optimized but the CPU usage is fine for your daily budget, I think you could ignore this warning without any concern.

Years ago, the number of High CPU Requests in a specific time was limited and the warning was useful to monitor and correct the application to stay above that specific quota; that limit was then removed and the High CPU warning is now useful just to identify part of the program that should be checked for optimization (where possible).

In practice, I've never had an issue with not enough instances being spun up to handle user requests even if I am running many longer-running jobs in the background [e.g., an expensive mapreduce job]. Of course, your budget needs to cover your CPU expenses or your app won't be able to operate.

However, I remember reading in the docs that if the majority of your requests take a long time, then app engine might not spin up additional instances to handle requests. However, if the majority of your requests are served quickly, then a minority of long-running jobs shouldn't cause any problems. (Unfortunately, I can't find the article/docs with the specific guidance on longer running requests at the moment.)