I was just thinking about this issue during an interview this morning. I like your initServlet idea and think that it could also be used during takedown to cleanup any external resources (like batched sequence counters).
An alternative for the scaling from 1 server to many startup problem is to not route the triggering request to the newly started service but rather keep the startup event trigger and route that request to an already warm service. Extra points for not routing any requests until the new instance is stabilized. On Thu, Sep 16, 2010 at 10:42 AM, Maxim Veksler <[email protected]> wrote: > Hey Guys, > > Just a quick 2.5cent idea. > > The current situation for applications running on the app engine is that a > request that causes instance spin up (be it first request, or the unlucky > one in high load) is usually cancelled because of timeout (30s). I'm > observing this situation even for "virgin" applications that do nothing more > then return "Hello World". > > Now, what if application developers could define a special API call (much > like mail delivery to the application is handled by GAE) that will be called > when GAE decides to spin yet another instance. This could solve the problem > of requests being "canceled" in high load while the new JVM instance is > loading. The GAE could allocate a "finite" amount of time from the "warm up" > call to the "start of request delivery" to the new jvm (something like 60 > seconds?). The application developers could take advantage of this call > (that will go to the "InitServlet") to do start up logic (population of > MemCache, loading static maps from DataStore and co..) > > This could be poor's men solution for applications that *should* not lose > requests, even if it's 1/100000. > > I know about the planned "reserved instances" feature, don't really see the > logic in this though as this approach doesn't seem to scale well: Say I'm > holding 5 reserved instances. What happens if my requests get a peak... a > truly massive slashdot peak which in theory should require yet another (well > just for ex.) 100 instances? If GAE launches them and instantly starts > forwarding requests to them then, assuming each instance takes 15sec to load > - ~(15sec*95instances*<amount of traffic coming in 1 sec>)*0.40 requests are > timed out. That's bad. > > > Comments? > > Maxim. > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to > [email protected]. > To unsubscribe from this group, send email to > [email protected]<google-appengine-java%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" 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-java?hl=en.
