Thanks Jon for the reply. After a few days of tinkering I can see how important it is to have that spare capacity. It's not fun to make a request that cold starts an instance.
On Sep 7, 3:35 am, Jon McAlister <[email protected]> wrote: > Hi Jon and Alexis, > > Indeed by default the scheduler will try to make space for spare > capacity in your frontend instances. There are usually two reasons for > this. > > The first is that requests do not usually come in regularly, they > arrive in spikes and various irregular patterns. In order to > comfortably handle the spikes without pending latency, an app needs > more instances than would be expected by purely multiplying qps and > latency. > > The second is that if the app were to receive more load, having spare > capacity is helpful to serve the additional load without pending > latency. > > The design of the scheduler is that the default automatic mode decides > to minimize pending latency, and provide excess spare capacity, to > help deal with the two issues explained above. Obviously, not all apps > will want this, especially in light of the new billing formula. This > is why there is now the ability to opt-out of this by using the > Performance Settings options of max-idle-instances and > min-pending-delay. With those options you can opt-out and signal to > the scheduler that pending latency and spare capacity are not as > important for your app as instance utilization. > > I hope that helps, > Jon > > > > > > > > On Tue, Sep 6, 2011 at 1:08 AM, Alexis <[email protected]> wrote: > > Hi, > > > I also have noticed something odd between QPS and latency, although my > > numbers are not as bad as yours. > > I generally have stats like this: > > > Total number of instances Average QPS* Average Latency* > > Average Memory > > 210 total 0.599 252.3 ms > > 72.1 MBytes > > > With a latency of 0.25sec, I'd expect to have a QPS close to 4, and > > hence reducing the number of instances needed. > > But QPS is still very low... > > > What makes QPS and Latency so different? > > > On 1 sep, 17:04, jon <[email protected]> wrote: > >> Hi guys, > > >> I may be missing something here but looking at the below screenshot of my > >> instances, it seems like GAE is overly eager to add instances. > > >> Each instance seems to be serving a request every 8 seconds approximately, > >> which feels high. Do the numbers look right to you? > > >> Thanks in advance, > >> Jonni > > >> <https://lh3.googleusercontent.com/-R73wUepWYAA/Tl-eYELjwMI/AAAAAAAAAA...> > > > -- > > 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 > > athttp://groups.google.com/group/google-appengine?hl=en. -- 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.
