[chef] Re: Re: Re: Launching spot instances?

[James < >]

Mike,

There are a number of ways to implement this, but it is not currently on my or our roadmap, so I haven't put much thought into how I would design it. I can say that this would benefit us, but not enough to warrant the effort currently. We don't generally use knife ec2 to provision on EC2, we're almost eliminating usage of EC2 org-wide, and in the use-case that is most important for us to use spot instances (map reduce), we do so using boto + custom stuff.  

Most single instance reservations I make get filled quickly, but you could definitely add some logic around this process in a number of different ways. You could allow a timeout to define when to stop waiting and cancel the bid. You could allow a price range as a parameter. I don't think any of the other knife compute gems support creating multiple instances simultaneously, so multiple instance reservations are probably not a necessary feature.

Your implementation could work for some use cases.

Spot instances are a really great way to drop the cost of EC2, just have to be aware of, and work around, limitations. 

James

On Fri, Oct 26, 2012 at 2:07 PM, Mike < " target="_blank"> > wrote:

James,

All the points about spot instances you reference are correct.

What I think I was trying to convey is that the behavior currently of
knife-ec2 is to perform the requested steps (provision, ssh,
bootstrap) in sequence, and exit upon completion.

How would you propose to do that with spot instances that are
_not_granted immediately? The request at the price is still made, and
will open up when available, but may not launch right now. There also
may be more than 1, and knife

Would the operator expect the shell session to remain open until _one_
spot instance is launched, so it can then perform bootstrapping, role
assignment etc? That is not a very tempting scenario to me.

I think a better use case for the _utterly specific_ use case of spot
instances would be to leverage AWS's api and model, potentially
pre-bake your own AMI with a default chef client.rb and validation.pem
for your organization (and roles?) , so that when a spot request
launches, it can boot, register with chef, get the latest cookbook
code and run until it's terminated.

That's why I don't think this is a good fit for `knife ec2 server create`.

On Fri, Oct 26, 2012 at 3:09 PM, Jeffrey Hulten < "> > wrote:
> I could see a "knife ec2 stack create" that used a default cloud formation stack json and passed in the parameters. This could be customized then to run spot instances.
>
> The issue with knife and spot instances is that they can take up to 15 minutes to start up. Basically (as I understand it) there is a batch job that takes the pool of bids and the available capacity and determines what to start and what to kill on a scheduled basis. That means that your request for spot instances cannot be instantaneous. This is not a model that the knife ec2 plugin can support.
>
> --
> Jeffrey Hulten
> Principal Consultant at Automated Labs, LLC
> ">  206-853-5216
> Skype: jeffhulten
>
> On Oct 25, 2012, at 6:56 AM, Mike wrote:
>
>> While the underlying library fog may provide this functionality, this
>> actually seems less useful to be part of the knife-ec2 command set.
>>
>> `knife ec2 server create` attempts to create an instance, wait for it
>> to come up, bootstrap it via ssh, and start up chef-client (usually).
>>
>> From what I garner, placing a spot request with a bid provide is not
>> ensured to be delivered at the time pf placing the request, and
>> therefore the flow of what "ec2 server create" does today would not be
>> the same, rather it seems like it would be: "If I can get a spot
>> request now, please give it to me, otherwise...?" Fail? The bid
>> request was probably placed, so this isn't a failure per se.
>>
>> The other part of why I think this might not be a great idea is:  Spot
>> instances come up and down whenever their bid price is met or outbid
>> respectively. This can cause easy buildup of cruft in your node/client
>> list if you are allowing these to auto-register/validate themselves,
>> and then have to clean up after them once they are gone.
>>
>> All in all, I think spot instances have a use case, but I don't know
>> if during ec2 server create (and subsequently bootstrap phase) makes
>> sense to support this.
>>
>>
>> On Wed, Oct 24, 2012 at 1:44 PM, Christopher J. Bottaro
>> < "> > wrote:
>>> How can I launch spot instances using "knife ec2 server create"?  I don't
>>> see any relevant command line switches.
>>>
>>> Thanks for the help.
>