My app is running on App engine Java SDK, and since this morning I noticed that open instances are not handling new requests, and instead, new Frontent instances are being started. So now i have about 250 open instances (a lot more than usual). Also, the instances are running on version 1.9.5.
Please advice!
The issue has been fixed by Google at 2014-05-09 10:15 (US Pacific Time). See Google App Engine Downtime Notify
How we fixed the issue temporarily: Disable and re-enable the application inside the Application Settings. After doing this everything went back to normal. Since then we only saw instances spawning with the version 1.9.4. In our case a lot of instances spawned again after 45 minutes.
To make sure you won't get billed choose a maximum of Idle Instances inside the Application Settings. We changed the maximum to 4 idle instances. In this case a lot of instances still stick around, but you don't get billed.
Our App Engine instances graph:
A workaround is: "Disable and re-enable the application inside the Application Settings" https://code.google.com/p/googleappengine/issues/detail?id=10893#c3
来源：https://stackoverflow.com/questions/23558319/app-engine-too-many-open-instances