The notification would be sent before it enters read-only state so there is time to save data as you assumed. We could write the capability state to a three layered cache (memory, memcache, and datastore).
But like you said, there are other ways to check this during a r-o mode and a quick memcache put might be the best way. I haven't research what is the optimal approach here. Regardless, that does not help us if we need to perform some work before entering r-o mode. Let's say that the notification is sent one hour in advance. Then we might want to: * Prioritize critical background processing work so it completes before the deadline. * Disable non-essential work to minimize overall workload when the app enters r-o mode. * Notify our users that our app will soon enter a r-o state and that features will be disabled. * Notify developers that missed the email for some reason (gmail marked it as spam, etc). * If the app is a service, notify other apps that it is to go offline. Of course, it would also help if the notification included an estimation of the downtime. Given the frequent downtimes, it is essential that there is a way to handle them more gracefully than the current approach allows. At least if we want to build non-toy apps. - Viðar On Tue, Jul 6, 2010 at 12:20 PM, Barry Hunter <[email protected]> wrote: > But what would you do with the notification? > You can't put it in memcache (memcache is usually disabled too) and, trying > to put it in the datastore (provided you can do it before it actully goes > read-only), will probably be no more efficient than trying a real write > anyway. > But that does lead to possibly a quick way to test, try a Memcache set. > "will instead return False for set() calls ..... In addition, memcache API > calls will return immediately during this period, without any additional > latency." > > 2010/7/6 Viðar Svansson <[email protected]> >> >> Hi >> >> It would be nice if AppEngine would post a message to our apps before >> it enters maintenance mode and again when it resumes to normal >> operation mode. This would allow us to disable features that require >> writing to the datastore. I realize we can catch the capability >> exceptions but that means we need to try to write first, which is not >> good enough IMO. >> >> Regards, >> Viðar >> >> On Sun, Jul 4, 2010 at 4:45 AM, Jan Z <[email protected]> wrote: >> > The last scheduled outages were arranged during the weekend - this >> > made life a great deal easier, particularly as the Capability API >> > wasn't working etc. >> > >> > Could we please aim to keep outages to weekends until we've gone >> > through a couple without any hitches? >> > >> > Thanks! >> > >> > J >> > >> > On Jul 1, 6:51 am, "Ikai L (Google)" <[email protected]> wrote: >> >> Hey guys, >> >> >> >> I just wanted to point out there are upcoming maintenance periods >> >> scheduled >> >> for July 7th and July 14th at 5pm Pacific. More details here: >> >> >> >> >> >> http://groups.google.com/group/google-appengine-downtime-notify/brows... >> >> >> >> Normally, I wouldn't post these notifications to this group, as they >> >> belong >> >> in the "downtime notify" group, however, users are reporting that this >> >> message went into their spam folder. Can anyone verify this, or let me >> >> know >> >> in this thread if this message was correctly delivered? >> >> >> >> If you want to be notified of upcoming maintenance periods, make sure >> >> to >> >> join this group: >> >> >> >> http://groups.google.com/group/google-appengine-downtime-notify >> >> >> >> We're doing our best to minimize these periods in the future, but there >> >> are >> >> times when these periods will be absolutely necessary. >> >> >> >> -- >> >> Ikai Lan >> >> Developer Programs Engineer, Google App Engine >> >> Blog:http://googleappengine.blogspot.com >> >> Twitter:http://twitter.com/app_engine >> >> Reddit:http://www.reddit.com/r/appengine >> > >> > -- >> > 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. >> > >> > >> >> -- >> 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. >> > > > > -- > Barry > > - www.nearby.org.uk - www.geograph.org.uk - > > -- > 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. > -- 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.
