Google App Engine: manual scaling with one instance suddenly created multiple instances (v2)

[Maccer]

Hi!

Since yesterday 2024-09-18 at around 10:40 PM (UTC+2), I again experience the same unexplainable issue mentioned in my old post (link below), where suddenly, multiple instances of my single-instance app engine app are created and won't disappear. They have at the time of writing been running for around 12 hours.

https://www.googlecloudcommunity.com/gc/Serverless/Google-App-Engine-manual-scaling-with-one-instanc...

I suspect the issue is on Google's side this time as well, and would appreciate if you could look into it!

[Maccer]

The issue seems to have solved itself around 18-20 hours later when the instances ramped down to 1 again. But I'm still curious to know why this occurred in the first place.

[ronnelg]

Hi @Maccer, 

I understand your frustration regarding your issue with the sudden increase of App Engine instances. This happens due to an incident affecting Google App Engine that increases latency and error rates that began at 2024-09-18 13:01 and ended at 2024-09-18 15:30 (US/Pacific) time affecting Asia, Europe and America.

Regarding why your App Engine instances suddenly went up and down is because App Engine automatically creates and shut down one or more instances if the traffic fluctuates, this is to handle the increasing load. You can check this documentation on How App Engine manages instances for your reference.

You can also visit this incident reported page from time to time to check for the status information of the services of Google Cloud.

I hope the above information is helpful.

[Maccer]

Hi @ronnelg ! 
Regarding this part of your reply:

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Regarding why your App Engine instances suddenly went up and down is because App Engine automatically creates and shut down one or more instances if the traffic fluctuates, this is to handle the increasing load. You can check this documentation on How App Engine manages instances for your reference.

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If my app would use automatic scaling or basic scaling with multiple instances, I would fully understand the behaviour that I see. But as I have explained in the previous post, my app is set to use manual_scaling with one instance, meaning that I ever expect to have one (and only one) instance running all the time.

I may have misunderstood, but I can't see that the documentation would say that there are circumstances where I would still get multiple instances. Am I missing something? If so, is there any way to force App Engine to never create more than one instance?

[ronnelg]

Hi @Maccer,

Yes, you are correct. It should not create multiple instances if only one instance Is set. I'm assuming you are using the App Engine Standard environment, right? Also, do you have a running old version of it? If so, I suggest you stop or delete it.

[Maccer]

No, old versions are set to automatically stop when the new is deployed, so there is only the latest version running. And it is that version that receives the erroneous start commands from Google.