Testing AMIs created with Packer

[Loren Gordon]

Hello,

I'd like to run tests using serverspec or testinfra against AMIs created using Packer. Is anyone doing something similar?

I looked at testkitchen with kitchen-ec2, but it feels pretty weak when it comes to setting up the AWS environment...for example, it doesn't create the ssh keypair or the security group, and so of course doesn't clean them up either. Meaning more setup/teardown that I'd have to manage myself. Packer's support for such things is pretty great, so it occurred to me that perhaps I could just use Packer to launch the instance and run the tests. However, it appears that the ebs builder will _always_ create an AMI and for the test run I wouldn't want another AMI. So I looked at the null builder, but that seems like it would require me to manage all the same things as testkitchen/kitchen-ec2.

I think, ideally, it would be handy if the ebs builder accepted something like "null" as an option for the ami_name, or just make it optional rather than required, indicating that the builder would not create an AMI or any other artifacts. Would anyone else be interested in such a feature?

Thanks,

-Loren

[Rickard von Essen]

First see https://github.com/hashicorp/packer/pull/4681

I have tried running serverspec for educational purposes with Packer.
First I thougth it should be a second step of a pipeline after
creating the AMI but after some considerations mostly about the time
it takes to launch a new instance and the overhead it adds I think
it's better to do the validation as the last step of your Packer
provisioning. You can eaither run serverspec localy on the instance
you are building or run it from the host running Packer.

If you want a second step in your pipeline Terraform might be a better option.

// Rickard

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[Loren Gordon]

Hi Rickard,

Thanks, that PR looks quite promising! Would you consider re-opening it?

I personally do not mind the extra time involved with launching a new instance and conducting the tests there. I considered running the tests within the packer instance, before creating the AMI, but our process makes it a little difficult... We use userdata to pivot /root to tmpfs (in memory), and then re-partition the root EBS volume and use chroot to complete the build. This is the only mechanism* we've found that allows us to re-partition the root volume and preserve the billing product code. So, I'm not sure what hurdles we'd run into getting the tests to execute against the chroot. (*Well, we could also chroot a secondary volume, then shutdown the instance, detach both root and secondary volumes, attach the secondary volume as root, and then create the image...but that is even more cumbersome and wouldn't address this problem.)

Also, the tests are sometimes dependent on the instance type, such as validating that the image is supporting detection of the network interface speed at 10Gbps. So we'd likely want to launch a new instance anyway, possibly several, to test different scenarios.

I can look into Terraform, also; I don't have any experience with it currently. Does it also handle the setup and teardown of resources around launching the instance, running some commands, and terminating the instance (i.e. create/delete keypair, security group, etc)? The EBS builder in Packer is _almost_ purpose-built for this...and there is already the null builder, which serves a sortof-similar use case.

Cheers,

-Loren

[Rickard von Essen]

> that PR looks quite promising! Would you consider re-opening it?

No, don't think we would. We want to keep the scope of Packer narrow. Ultimately this is a HashiCorp decision (which I'm not an employee of). 

> I personally do not mind the extra time involved with launching a new instance and conducting the tests there.

Ok good then Terraform will work nicely  for you. 

> We use userdata to pivot /root to tmpfs (in memory), and then re-partition the root EBS volume and use chroot to complete the build. This is the only mechanism* we've found that allows us to re-partition the root volume and preserve the billing product code.

You can probably use the chroot builder too. 

> So, I'm not sure what hurdles we'd run into getting the tests to execute against the chroot.

Agree

> Also, the tests are sometimes dependent on the instance type, such as validating that the image is supporting detection of the network interface speed at 10Gbps. So we'd likely want to launch a new instance anyway, possibly several, to test different scenarios.

> I can look into Terraform, also; I don't have any experience with it currently. Does it also handle the setup and teardown of resources around launching the instance, running some commands, and terminating the instance (i.e. create/delete keypair, security group, etc)? 

Terraform is a awesome tool to learn and not that hard to get started with. You will have to define all your infra from the test and then you create (apply) and after the tests have completed you run destroy and it will remove everything. 

Test should run as provisioning on the aws_ec2_instance. 

Regards 

Rickard 

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[Loren Gordon]

You can probably use the chroot builder too. 

Tried it, doesn't work. It uses register-image, which cannot maintain the product billing code. Only create-image works.

Terraform is a awesome tool to learn and not that hard to get started with. You will have to define all your infra from the test and then you create (apply) and after the tests have completed you run destroy and it will remove everything. 

Well, I started looking into Terraform since my post, but it doesn't really look like a great fit to me. I'm struggling even to find any examples of anyone doing anything similar. All the examples are _way_ more complicated than we need. At the moment, it appears simpler just to use the EBS builder with Packer, and de-register the unneeded AMIs after the fact. Pretty silly. :(

Cheers,

-Loren