Background
I was kind of dropped into an IaC project that uses Packer => Terraform => Ansible to create RHEL Virtual Machines on an on-prem VMware Vsphere cluster.
Our vmware module registers output variables that we use once the VMs are created, those variables feed a local_file resource template to build an Ansible inventory with the vm names and some other variables.
Ansible is then run using local_exec with the above created inventory to do configuration actions and run scripts both on the newly deployed VM's and against some external management applications, for example to join the VM to a domain (FreeIPA, sadly no TF good provider is available).
Issue Description
The issue that I have been wrestling with is when we run a terraform destroy (or apply with some VM count changes that destroy a VM resource), we would like to be able to repeat the process in reverse.
Capture the names of the VMs to be destroyed(Output vars from resource creation) so they can be removed from the IPA domain and have some general cleanup.
We've tried different approaches with Destroy Time Provisioners and it just seems like it would require a fundamental change in the approach outlined above to make that work.
Question
I'm wondering if there is a way to get an output variable on destroy that could be used to populate a list the VMs that would be removed.
So far my search has turned up nothing. Thanks for your time.
In general, it is good to plan first, even when destroying:
terraform plan -destroy -out tfplan
Then, you you can proceed with the destroy:
terraform apply tfplan
But at this moment (or before actual destroy), you have a plan what was destroyed, and you can do any analysis or automation on it. Example:
terraform show -json tfplan | jq > tfplan.json
Source:
https://learn.hashicorp.com/tutorials/terraform/plan
Am using a combination of these tools
Terraform - To deploy the Application specific AWS resources I need
(For instance a secret)
Skaffold - To help with the inner
development loop, surrounding the deployment of K8s resources to
local and remote cluster
Kustomize - To help with templating of
different configurations for different environment
My github action steps are as follows
Terraform to create the AWS resources. At this point it creates a AWS
secrets arn.
Skaffold to deploy the k8s manifests. Skaffold in-turn delegates K8s manifest generation to Kustomize. Within the Kustomize overlay files i need to be able to access the Secrets arn that was created earlier, this arn needs to be injected into the container that is being deployed. How do I achieve this?
Rephrasing the question: How do I pass resources that were created by terraform to be consumed by something like Kustomize (Which is used by skaffold)
(p.s, I really like the choice of my tools thus far as each one excels at one thing. I realize that terraform can possibly do all of it, but that is a choice that I dont want to make unless there are no easier options)
Here is what I have learnt:
I don't think there are any industry standards in terms of how to share this data between the tools across different steps within github actions. That being said here are some of the options
Have the Terraform store the secrets arn in a parameter store. Retrieve the arn from the parameter store in later steps. This means that the steps have to share a static key
Have Terraform update the kustomize files directly (or use kustomize_overlays as datasource)
There could be other similar approaches, but none of these tools have a native way of passing/sharing data
I have written a Terraform script to spin-up an infrastructure on Azure. I have also written an Ansible script to patch the VMs launched on Azure with latest updates. But when I am not able to automate the process of patching the VMs once they get launched.
You can use Provisioners in Terraform to execute Ansible Playbooks on Provisioned VM. I'm not sure about your terraform Version. But below code might help. Keep in mind Provisioners are to be used as last resort
provisioner "local-exec" {
command = "ansible-playbook -u user -i '${self.public_ip},' --private-key ${var.ssh_key_private} provision.yml"
}
https://www.terraform.io/docs/language/resources/provisioners/syntax.html
To have end-to-end automation in which the Ansible is run when the instances are launched (and/or at every restart) you can pass in cloud-init configuration from Terraform. This is nice because that config may be referencing other parts of your infrastructure which can be sorted out by Terraform's dependency resolution. You would do this by providing Terraform cloudinit_config to the custom_data argument of the Azure VM in Terraform.
On the Ansible side you can also use the Azure dynamic inventory. With this dynamic inventory you add tags to your resources in Terraform in such a way that they can be filtered and grouped into the Ansible inventory when Ansible is run. This is helpful if the Ansible tasks need to gather facts from hosts.
I wrote infrastructure as code using terraform, and apply it successfully on azure cloud, now i created another 3 vm's using the same networking file and variable file that already used in the pervious IAAC, how can i run only these 3 vm's without generating new error, or "already exists" to create them on the same subscription and same variable/networking configuration.
Thanks
if you understand correctly, you can use
terraform -target
Be notice that -target attribute respects dependencies
Being able to capture infrastructure in a single Terraform file has obvious benefits. However, I am not clear in my mind how - once, for example, a virtual machine has been created - subsequent updates are handled.
So, to provide a specific scenario. Suppose that using Terraform we set up an Azure vm with SQL Server 2014. Then, after a month we decide that we should like to update that vm with the latest service pack for SQL Server 2014 that has just been released.
Is the recommended practice that we update the Terraform configuration file and re-apply it?
I have to disagree with the other two responses. Terraform can handle infrastructure updates just fine. The key thing to understand, however, is that Terraform largely follows an immutable infrastructure paradigm, which means that to "update" a resource, you delete the old resource and create a new one to replace it. This is much like functional programming, where variables are immutable, and to "update" something, you actually create a new variable.
The typical pattern with Terraform is to use it to deploy a server image, such as an Virtual Machine (VM) Image (e.g. an Amazon Machine Image (AMI)) or a Container Image (e.g. a Docker Image). When you want to "update" something, you create a new version of your image, deploy that onto a new server, and undeploy the old server.
Here's an example of how that works:
Imagine that you're building a Ruby on Rails app. You get the app working in dev and it's time to deploy to prod. The first step is to package the app as an AMI. You could do this using a tool like Packer. Now you have an AMI with id ami-1234.
Here is a Terraform template you could use to deploy this AMI on a server (an EC2 Instance) in AWS with an Elastic IP Address attached to it:
resource "aws_instance" "example" {
ami = "ami-1234"
instance_type = "t2.micro"
}
resource "aws_eip" "example" {
instance = "${aws_instance.example.id}"
}
When you run terraform apply, Terraform deploys the server, attaches an IP address to it, and now when users visit that IP, they will see v1 of your Rails app.
Some time later, you update your Rails app and want to deploy the new version, v2. To do that, you build a new AMI (i.e. you run Packer again) to get an ami with ID "ami-5678". You update your Terraform templates accordingly:
resource "aws_instance" "example" {
ami = "ami-5678"
instance_type = "t2.micro"
}
When you run terraform apply, Terraform undeploys the old server (which it can find because Terraform records the state of your infrastructure), deploys a new server with the new AMI, and now users will see v2 of your code at that same IP.
Of course, there is one problem here: in between the time when Terraform undeploys v1 and when it deploys v2, your users would see downtime. To work around that, you could use Terraform's create_before_destroy lifecycle setting:
resource "aws_instance" "example" {
ami = "ami-5678"
instance_type = "t2.micro"
lifecycle {
create_before_destroy = true
}
}
With create_before_destroy set to true, Terraform will create the replacement server first, switch the IP to it, and then remove the old server. This allows you to do zero-downtime deployment with immutable infrastructure (note: zero-downtime deployment works better with a load balancer that can do health checks than a simple IP address, especially if your server takes a long time to boot).
For more information on this, check out the book Terraform: Up & Running. The code samples for the book include an example of a zero-downtime deployment with a cluster of servers and a load balancer: https://github.com/brikis98/terraform-up-and-running-code
Terraform is an infrastructure provision tool, th configuration/deployment tools will be:
chef
saltstack
ansible
etc.,
As I am working with chef, so basically, I provision the server instance by terraform, then terraform (terraform provisioner) handles the control to chef for system configuration and deployment.
For the moment, terraform cannot delete the node/client in chef server, so after you terraform destroy, you need remove them by yourself.
Terraform isn't best placed for this sort of task. Terraform is an infrastructure management tool, not configuration management.
You should use tools such as chef, puppet, and ansible to deal with the configuration of the system.
If you must use terraform for this task; you could create a template_file resource and place in the configuration required to install the SQL server, and how to upgrade if a different version is presented. Reference: here
Put that code inside a provisioner under the null_resource resource. reference: here.
The trigger for this could be the variable containing the SQL version. So, when you present a different version of SQL it'll execute that provisioner on each instance to upgrade the versions.