On Thu, Sep 8, 2011 at 6:56 AM, Joshua Smith <joshuaesm...@charter.net> wrote: > I take issue with this: > On Sep 8, 2011, at 6:07 AM, Tim wrote: > > - An instance starts when either > - it is needed to serve a request (there are no IDLE or FREE-IDLE > instances available subject to max-pending-latency) - starts in ACTIVE state > > I have seen cases where an instance starts for no apparent reason. In my > case, I'm bumping along with just one instance most of the time. Every now > and then, the scheduler starts a second instance, even though the first one > is still responding quickly and hasn't handled a request in a few seconds. > My theories are: > - There is a race condition, data sync, or timing issue, which causes the > schedule to sometimes think an instance is busy when it isn't; or, > - There are heuristics in the scheduler which predict an increase in load, > and act proactively (such as a request coming in from a new IP address) > My details are in the thread "Scheduler Bug or Inscrutable Scheduler > "Feature"". No response from our google overlords on that one.
I thought I did respond... In any event, for the reasons you listed above and others, this is why max-idle-instances is important. It ensures that you are not held accountable for scheduler behaviors such as these listed. When you set it, the billable-instances-rate is determined by max-idle-instances (a setting you directly control) and active-instances-rate (again, hopefully something you control). The nuances of how the scheduler spins up extra instances to minimize latency and provide spare capacity are not part of the formula, other than their effect on your serving latency and reliability. > Another case was reported as well, although he had hundreds of instances > running, so it would be a lot harder to grok the state of the system in his > case. > -Joshua > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To post to this group, send email to google-appengine@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine+unsubscr...@googlegroups.com. > For more options, visit this group at > http://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 google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
