[LRUG] Idempotency vs the cloud

[Adrian Sevitz]

We do exactly the same thing. It's improved our auto-scaling speed by a facto or 5x. 

We get the speed of a baked instance, but the benefit of using chef.

We're very happy with this process and it's serving us well.



On 17 Jul 2013, at 15:33, chat-request at lists.lrug.org wrote:

> On 17 Jul 2013, at 14:55, David Nolan <dave at textgoeshere.org.uk> wrote:
>> 
>> I'd love my servers to be truly ephemeral. Sadly our Chef recipes are still littered with only_if/not_if conditions to ensure idempotence. The main reasons being
>> 
>> - Data gets harder to shift about the more of it you have
>> - If you do several deploys a day to a cloud you pay for in blocks of 1 full hour, it gets expensive to be merciless
>> - It's slow to boot a fresh node/server relative to converging an existing one
> 
> I do a halfway house for app servers for the last 2 reasons, so a deploy of the app is just a 'normal' deploy. However the app is deployed to a separate volume than the boot volume which we then snapshot. On EC2 this means we can then bring up new instances quickly and simply: bake a new instance from an AMI and create a new app volume from the latest snapshot (and this works with autoscaling groups and all that sort of stuff). We use this so that autoscaling can replace dead instances/respond to traffic increases recently and we also do a lot of our overnight processing on temporary instances.
> 
> Fred


_____________
Adrian Sevitz
CTO, vzaar.com

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