Automating Deployment of Flask and PostgreSQL on KVM with Terraform and Ansible

? Intro

Hi, in this post, we will use Libvirt with Terraform to provision 2 KVM locally and after that, we will Deploy Flask App & PostgreSQL using Ansible.

Content

• Project Architecture
• Requirements
• Create KVM
• Create Ansible Playbook
  • Playbook to install Docker
  • Playbook to install and configure postgresql
  • Playbook to deploy Flask App
  • Run Playbook and testing
• Conclusion

? Project Architecture

So we will create 2 VMs using Terraform, then deploy a Flask project and the database using Ansible.

? Requirements

I used Ubuntu 22.04 LTS as the OS for this project. If you're using a different OS, please make the necessary adjustments when installing the required dependencies.

The major pre-requisite for this setup is KVM hypervisor. So you need to install KVM in your system. If you use Ubuntu you can follow this step:

sudo apt -y install bridge-utils cpu-checker libvirt-clients libvirt-daemon qemu qemu-kvm

Execute the following command to make sure your processor supports virtualisation capabilities:

$ kvm-ok

INFO: /dev/kvm exists
KVM acceleration can be used

Install Terraform

$ wget -O - https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg
$ echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
$ sudo apt update && sudo apt install terraform -y

Verify installation:

$ terraform version

Terraform v1.9.8
on linux_amd64

Install Ansible

$ sudo apt update
$ sudo apt install software-properties-common
$ sudo add-apt-repository --yes --update ppa:ansible/ansible
$ sudo apt install ansible -y

Verify installation:

$ ansible --version

ansible [core 2.15.1]
...

Create KVM

we will use the libvirt provider with Terraform to deploy a KVM Virtual Machine.

Create main.tf, just specify the provider and version you want to use:

terraform {
  required_providers {
    libvirt = {
      source = "dmacvicar/libvirt"
      version = "0.8.1"
    }
  }
}

provider "libvirt" {
  uri = "qemu:///system"
}

Thereafter, run terraform init command to initialize the environment:

$ terraform init

Initializing the backend...
Initializing provider plugins...
- Reusing previous version of hashicorp/template from the dependency lock file
- Reusing previous version of dmacvicar/libvirt from the dependency lock file
- Reusing previous version of hashicorp/null from the dependency lock file
- Using previously-installed hashicorp/template v2.2.0
- Using previously-installed dmacvicar/libvirt v0.8.1
- Using previously-installed hashicorp/null v3.2.3

Terraform has been successfully initialized!

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.

If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.

Now create our variables.tf. This variables.tf file defines inputs for the libvirt disk pool path, the Ubuntu 20.04 image URL as OS for the VMs , and a list of VM hostnames.

variable "libvirt_disk_path" {
  description = "path for libvirt pool"
  default     = "default"
}

variable "ubuntu_20_img_url" {
  description = "ubuntu 20.04 image"
  default     = "https://cloud-images.ubuntu.com/releases/focal/release/ubuntu-20.04-server-cloudimg-amd64.img"
}

variable "vm_hostnames" {
  description = "List of VM hostnames"
  default     = ["vm1", "vm2"]
}

Let's update our main.tf:

resource "null_resource" "cache_image" {
  provisioner "local-exec" {
    command = "wget -O /tmp/ubuntu-20.04.qcow2 ${var.ubuntu_20_img_url}"
  }
}

resource "libvirt_volume" "base" {
  name   = "base.qcow2"
  source = "/tmp/ubuntu-20.04.qcow2"
  pool   = var.libvirt_disk_path
  format = "qcow2"
  depends_on = [null_resource.cache_image]
}
# Volume for VM with size 10GB
resource "libvirt_volume" "ubuntu20-qcow2" {
  count          = length(var.vm_hostnames)
  name           = "ubuntu20-${count.index}.qcow2"
  base_volume_id = libvirt_volume.base.id
  pool           = var.libvirt_disk_path
  size           = 10737418240  # 10GB
}

data "template_file" "user_data" {
  count    = length(var.vm_hostnames)
  template = file("${path.module}/config/cloud_init.yml")
}

data "template_file" "network_config" {
  count    = length(var.vm_hostnames)
  template = file("${path.module}/config/network_config.yml")
}

resource "libvirt_cloudinit_disk" "commoninit" {
  count          = length(var.vm_hostnames)
  name           = "commoninit-${count.index}.iso"
  user_data      = data.template_file.user_data[count.index].rendered
  network_config = data.template_file.network_config[count.index].rendered
  pool           = var.libvirt_disk_path
}

resource "libvirt_domain" "domain-ubuntu" {
  count  = length(var.vm_hostnames)
  name   = var.vm_hostnames[count.index]
  memory = "1024" # VM memory
  vcpu   = 1 # VM CPU

  cloudinit = libvirt_cloudinit_disk.commoninit[count.index].id

  network_interface {
    network_name   = "default"
    wait_for_lease = true
    hostname       = var.vm_hostnames[count.index]
  }

  console {
    type        = "pty"
    target_port = "0"
    target_type = "serial"
  }

  console {
    type        = "pty"
    target_type = "virtio"
    target_port = "1"
  }

  disk {
    volume_id = libvirt_volume.ubuntu20-qcow2[count.index].id
  }

  graphics {
    type        = "spice"
    listen_type = "address"
    autoport    = true
  }
}

the script will provisions multiple KVM VMs using the Libvirt provider. It downloads an Ubuntu 20.04 base image, clones it for each VM, configures cloud-init for user and network settings, and deploys VMs with specified hostnames, 1GB memory, and SPICE graphics. The setup dynamically adapts based on the number of hostnames provided in var.vm_hostnames.

As I've mentioned, I'm using cloud-init, so lets setup the network config and cloud init under the config directory:

mkdir config/

Then create our config/cloud_init.yml, just make sure that you configure your public ssh key for ssh access in the config:

#cloud-config
runcmd:
  - sed -i '/PermitRootLogin/d' /etc/ssh/sshd_config
  - echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
  - systemctl restart sshd
ssh_pwauth: true
disable_root: false
chpasswd:
  list: |
    root:cloudy24
  expire: false
users:
  - name: ubuntu
    gecos: ubuntu
    groups:
      - sudo
    sudo:
      - ALL=(ALL) NOPASSWD:ALL
    home: /home/ubuntu
    shell: /bin/bash
    lock_passwd: false
    ssh_authorized_keys:
      - ssh-rsa AAAA...

And then network config, in config/network_config.yml:

version: 2
ethernets:
  ens3:
    dhcp4: true

Our project structure should look like this:

sudo apt -y install bridge-utils cpu-checker libvirt-clients libvirt-daemon qemu qemu-kvm

Now run a plan, to see what will be done:

$ kvm-ok

INFO: /dev/kvm exists
KVM acceleration can be used

And run terraform apply to run our deployment:

$ wget -O - https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg
$ echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
$ sudo apt update && sudo apt install terraform -y

Verify VM creation using virsh command:

$ terraform version

Terraform v1.9.8
on linux_amd64

Get instances IP address:

$ sudo apt update
$ sudo apt install software-properties-common
$ sudo add-apt-repository --yes --update ppa:ansible/ansible
$ sudo apt install ansible -y

Try to access the vm using ubuntu user:

$ ansible --version

ansible [core 2.15.1]
...

Create Ansible Playbook

Now let's create the Ansible Playbook to deploy Flask & Postgresql on Docker. First you need to create ansible directory and ansible.cfg file:

terraform {
  required_providers {
    libvirt = {
      source = "dmacvicar/libvirt"
      version = "0.8.1"
    }
  }
}

provider "libvirt" {
  uri = "qemu:///system"
}

$ terraform init

Initializing the backend...
Initializing provider plugins...
- Reusing previous version of hashicorp/template from the dependency lock file
- Reusing previous version of dmacvicar/libvirt from the dependency lock file
- Reusing previous version of hashicorp/null from the dependency lock file
- Using previously-installed hashicorp/template v2.2.0
- Using previously-installed dmacvicar/libvirt v0.8.1
- Using previously-installed hashicorp/null v3.2.3

Terraform has been successfully initialized!

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.

If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.

Then create inventory file called hosts:

variable "libvirt_disk_path" {
  description = "path for libvirt pool"
  default     = "default"
}

variable "ubuntu_20_img_url" {
  description = "ubuntu 20.04 image"
  default     = "https://cloud-images.ubuntu.com/releases/focal/release/ubuntu-20.04-server-cloudimg-amd64.img"
}

variable "vm_hostnames" {
  description = "List of VM hostnames"
  default     = ["vm1", "vm2"]
}

checking our VMs using ansible ping command:

resource "null_resource" "cache_image" {
  provisioner "local-exec" {
    command = "wget -O /tmp/ubuntu-20.04.qcow2 ${var.ubuntu_20_img_url}"
  }
}

resource "libvirt_volume" "base" {
  name   = "base.qcow2"
  source = "/tmp/ubuntu-20.04.qcow2"
  pool   = var.libvirt_disk_path
  format = "qcow2"
  depends_on = [null_resource.cache_image]
}
# Volume for VM with size 10GB
resource "libvirt_volume" "ubuntu20-qcow2" {
  count          = length(var.vm_hostnames)
  name           = "ubuntu20-${count.index}.qcow2"
  base_volume_id = libvirt_volume.base.id
  pool           = var.libvirt_disk_path
  size           = 10737418240  # 10GB
}

data "template_file" "user_data" {
  count    = length(var.vm_hostnames)
  template = file("${path.module}/config/cloud_init.yml")
}

data "template_file" "network_config" {
  count    = length(var.vm_hostnames)
  template = file("${path.module}/config/network_config.yml")
}

resource "libvirt_cloudinit_disk" "commoninit" {
  count          = length(var.vm_hostnames)
  name           = "commoninit-${count.index}.iso"
  user_data      = data.template_file.user_data[count.index].rendered
  network_config = data.template_file.network_config[count.index].rendered
  pool           = var.libvirt_disk_path
}

resource "libvirt_domain" "domain-ubuntu" {
  count  = length(var.vm_hostnames)
  name   = var.vm_hostnames[count.index]
  memory = "1024" # VM memory
  vcpu   = 1 # VM CPU

  cloudinit = libvirt_cloudinit_disk.commoninit[count.index].id

  network_interface {
    network_name   = "default"
    wait_for_lease = true
    hostname       = var.vm_hostnames[count.index]
  }

  console {
    type        = "pty"
    target_port = "0"
    target_type = "serial"
  }

  console {
    type        = "pty"
    target_type = "virtio"
    target_port = "1"
  }

  disk {
    volume_id = libvirt_volume.ubuntu20-qcow2[count.index].id
  }

  graphics {
    type        = "spice"
    listen_type = "address"
    autoport    = true
  }
}

Now create playbook.yml and roles, this playbook will install and configure Docker, Flask and PostgreSQL:

mkdir config/

Playbook to install Docker

Now create new directory called roles/docker:

#cloud-config
runcmd:
  - sed -i '/PermitRootLogin/d' /etc/ssh/sshd_config
  - echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
  - systemctl restart sshd
ssh_pwauth: true
disable_root: false
chpasswd:
  list: |
    root:cloudy24
  expire: false
users:
  - name: ubuntu
    gecos: ubuntu
    groups:
      - sudo
    sudo:
      - ALL=(ALL) NOPASSWD:ALL
    home: /home/ubuntu
    shell: /bin/bash
    lock_passwd: false
    ssh_authorized_keys:
      - ssh-rsa AAAA...

Create a new directory in docker called tasks, then create new file main.yml. This file will install Docker & Docker Compose:

version: 2
ethernets:
  ens3:
    dhcp4: true

$ tree
.
├── config
│   ├── cloud_init.yml
│   └── network_config.yml
├── main.tf
└── variables.tf

Playbook to install and configure postgresql

Then create new directory called psql, create subdirectory called vars, tempalates & tasks:

$  terraform plan

data.template_file.user_data[1]: Reading...
data.template_file.user_data[0]: Reading...
data.template_file.network_config[1]: Reading...
data.template_file.network_config[0]: Reading...
...

Plan: 8 to add, 0 to change, 0 to destroy

After that, in vars, create main.yml. These are variables used to set username, passwords, etc:

$ terraform apply

...
null_resource.cache_image: Creation complete after 10m36s [id=4239391010009470471]
libvirt_volume.base: Creating...
libvirt_volume.base: Creation complete after 3s [id=/var/lib/libvirt/images/base.qcow2]
libvirt_volume.ubuntu20-qcow2[1]: Creating...
libvirt_volume.ubuntu20-qcow2[0]: Creating...
libvirt_volume.ubuntu20-qcow2[1]: Creation complete after 0s [id=/var/lib/libvirt/images/ubuntu20-1.qcow2]
libvirt_volume.ubuntu20-qcow2[0]: Creation complete after 0s [id=/var/lib/libvirt/images/ubuntu20-0.qcow2]
libvirt_domain.domain-ubuntu[1]: Creating...
...

libvirt_domain.domain-ubuntu[1]: Creation complete after 51s [id=6221f782-48b7-49a4-9eb9-fc92970f06a2]

Apply complete! Resources: 8 added, 0 changed, 0 destroyed

Next, we will create jinja file called docker-compose.yml.j2. With this file we will create postgresql container:

$ virsh list

 Id   Name   State
----------------------
 1    vm1    running
 2    vm2    running

Next, create main.yml to tasks. So we will copy docker-compose.yml.j2 and run using docker compose:

$ virsh net-dhcp-leases --network default

Expiry Time           MAC address         Protocol   IP address          Hostname   Client ID or DUID
-----------------------------------------------------------------------------------------------------------------------------------------------
2024-12-09 19:50:00   52:54:00:2e:0e:86   ipv4       192.168.122.19/24   vm1        ff:b5:5e:67:ff:00:02:00:00:ab:11:b0:43:6a:d8:bc:16:30:0d
2024-12-09 19:50:00   52:54:00:86:d4:ca   ipv4       192.168.122.15/24   vm2        ff:b5:5e:67:ff:00:02:00:00:ab:11:39:24:8c:4a:7e:6a:dd:78

Playbook to deploy Flask App

First, you need to create directory called flask, then create sub-directory again:

$ ssh ubuntu@192.168.122.15

The authenticity of host '192.168.122.15 (192.168.122.15)' can't be established.
ED25519 key fingerprint is SHA256:Y20zaCcrlOZvPTP+/qLLHc7vJIOca7QjTinsz9Bj6sk.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.122.15' (ED25519) to the list of known hosts.
Welcome to Ubuntu 20.04.6 LTS (GNU/Linux 5.4.0-200-generic x86_64)
...

ubuntu@ubuntu:~$

Next, add main.yml to vars. This file refer to posgtresql variable before, with addition IP address of VM2(database VM):

$ mkdir ansible && cd ansible

Next, create config.py.j2 to templates. This file will replace the old config file from Flask project:

[defaults]
inventory = hosts
host_key_checking = True
deprecation_warnings = False
collections = ansible.posix, community.general, community.postgresql

Next, create docker-compose.yml.j2 to templates. With this file we will create a container using docker compose:

[vm1]
192.168.122.19 ansible_user=ubuntu

[vm2]
192.168.122.15 ansible_user=ubuntu

Next, create main.yml in tasks. With this file we will clone flask project, add compose file, replace config.py and create new container using docker compose:

$ ansible -m ping all

192.168.122.15 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}
192.168.122.19 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    },
    "changed": false,
    "ping": "pong"
}

Our project structure should look like this:

---
- name: Deploy Flask
  hosts: vm1
  become: true
  remote_user: ubuntu
  roles:
    - flask
    - config

- name: Deploy Postgresql
  hosts: vm2
  become: true
  remote_user: ubuntu
  roles:
    - psql
    - config

Run Playbook and testing

Finally, let's run ansible-playbook to deploy PostgreSQL and Flask:

$ mkdir roles
$ mkdir docker

After complete, just make sure there is no error. Then you see there are two created. In VM1 is Flask and VM2 is Postgresql:

sudo apt -y install bridge-utils cpu-checker libvirt-clients libvirt-daemon qemu qemu-kvm

Try to access the app using browsers, just type http://:

Try to add a new task and then the data will be added to the database:

Conclusion

Finally, thank you for reading this article. Feel free to leave a comment if you have any questions, suggestions, or feedback.

Nb: Project Repo: danielcristho/that-i-write

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