Thanks Anastasios Hatzis for the detailed explanation. That threw some
light on my understanding of Instance Hours. You said,
If I understand idle instances correctly, that means that at least three
> instances will be running that do nothing. If your cron-job starts, a
> fourth instance would be started, so there will always be three idle
> instances, plus the instances that are processing the cron-jobs.
>
Does that mean that min-idle-instances are always idle ? And won't take up
any requests to process ? Why will a fourth instance be started when we
already have three idle instances ? What does min-idle-instances signify ?
Now, we have enabled max-idle-instances to 3 as well. So, the instance
hours with this setup {min-idle: 3, max-idle: 3}, should come up to 24 * 3
* 6 = 432 F1 Instance Hours, And I should not be charged for any dynamic
instances that will spin up beyond 3. Correct me if I am wrong.
Thank you very much.
On Friday, 23 October 2015 16:37:31 UTC+5:30, Anastasios Hatzis wrote:
>
> There might be more than one reason for this:
>
> From the documentation
> <https://cloud.google.com/appengine/docs/python/modules/#instance_classes>
> :
>>
>> *Important:* When you are billed for instance hours, you will not see
>> any instance classes in your billing line items. Instead, you will see the
>> appropriate multiple of instance hours. For example, if you use an F4
>> instance for one hour, you do not see "F4" listed, but you will see billing
>> for four instance hours at the F1 rate.
>
>
> So in your case with *F4_1G*, which costs 0.30$ per hour, rather than
> 0.05$ per hour of a *B1* instance, this is factor 6. The billings always
> show instance hours as B1, so 72 hours F4_1G translates to 432 hours B1.
> The same applies to the billing dashboard.
>
> However, there can indeed be more instances with your setup, than the 3
> you want, hence the "min-idle-instances":
>
> From the docs <https://cloud.google.com/appengine/docs/scaling>:
>
>> Auto scaling modules use dynamic instances - but if you specify a number,
>> N, of minimum idle instances, the first N instances will be resident, and
>> additional dynamic instances will be created as necessary.
>
>
> For example, if your cron job handler has an error and exponentially adds
> tasks into the queue. Or if tasks run much longer than expected, so
> additional instances are needed to handle the overlapping tasks. With your
> setup it is possible that you end up with more than three *F4_1G*
> instances during peeks, but never will fall below three. If I understand
> idle instances correctly, that means that at least three instances will be
> running that do nothing. If your cron-job starts, a fourth instance would
> be started, so there will always be three idle instances, plus the
> instances that are processing the cron-jobs.
>
> You can limit this, either in auto-scaling (e.g. max_idle_instances
> <https://cloud.google.com/appengine/docs/python/modules/#Python_Instance_scaling_and_class>),
>
> or kind of ultimately, you can set a daily budget. I recommend to check
> again the dashboard from your screenshot, just to be certain what the
> reason is for your instance hours. There is the "Summary" button on top.
> Toggle it to "Instances" diagram and switch the period to 1 day, for
> example, just to see if there were any peeks with more than 3 instances.
>
> As far as I understand, you have no user-facing features in your app (or
> this module), but only cron-jobs? Do you expect to have always same load
> for your app or module? Maybe it doesn't matter if your cron-jobs have to
> wait a few additional seconds until a new instance is spawned (just in
> case). If the answers are all yes, you could consider basic-scaling with
> max-instances set to 3. If you set the idle_timeout to something longer
> than your 5 minute cron-job schedule (e.g. 10m), the setup could work fine
> for your use-case.
>
>
> On Friday, October 23, 2015 at 7:41:00 AM UTC+2, Naresh Pokuri wrote:
>>
>> I have started my GAE app with *Auto-scaling* having *min-idle-instances
>> 3*, each with 1GB RAM and 2.4GHz processor(i.e *F4_1G*). And I have a
>> cron job which runs on every 5 minutes. With this setup keeping application
>> idle for one day should equal to 72 instance hours. But I see that it
>> already reached 428 instance hours. So, I am clueless here how GAE
>> calculates instance hours, with this alone I can keep my budget in control.
>> Can someone help me in this *instance hours*
>>
>
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