Deployment of 3-tier web app using ansible

In the project we deploy 3-tier web app with help of ansible-playbook tool. Web app consists of the following components:

• nginx
• uSWGI + Python (Flask)
• Postgres

Prerequisites

We need Linux Ubuntu server 18.04 LTS with running sshd service. The server plays Ansible Host role.

Setup Ansible Host

Let's implement Ansible Host as a Docker container.

1. Build a Docker image.

[webapp_ansible_deploy]% docker build -t ubuntu-sshd:18.04 .

There is a Dockerfile for this:

# Base image
FROM ubuntu:18.04

# Install packets
RUN apt-get update && apt-get install -y python openssh-server

# To set up SSHd service in a container
RUN mkdir /var/run/sshd
RUN echo 'root:secret' | chpasswd
RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config

# SSH login fix. Otherwise user is kicked off after login
RUN sed 's@session\s*required\s*pam_loginuid.so@session optional pam_loginuid.so@g' -i /etc/pam.d/sshd

ENV NOTVISIBLE "in users profile"
RUN echo "export VISIBLE=now" >> /etc/profile

EXPOSE 22

CMD ["/usr/sbin/sshd", "-D"]

2. Create and start a container

Actually, this is an optional stage which can be implemented by ansible task Start the container 'ubuntu_18.04' if it's not up.

[webapp_ansible_deploy]$ docker run -d -p 127.0.0.1:22:22 --name ubuntu_18.04 ubuntu-sshd:18.04

Check if the container is up:

[webapp_ansible_deploy]$ docker ps
CONTAINER ID        IMAGE               COMMAND               CREATED             STATUS              PORTS                  NAMES
9381672c0d12        ubuntu-sshd:18.04   "/usr/sbin/sshd -D"   5 seconds ago       Up 4 seconds        127.0.0.1:22->22/tcp   ubuntu_18.04

We have to be able to connect to the container's SSHd service via 127.0.0.1:22 host socket.

Deployment

1. Setup use of 10.0.0.2/16 static IP address, Netmask 255.255.0.0, gateway 10.0.0.1/16

Create ansible role container-net-setup.

./roles/container-net-setup/tasks/main.yml:

---
- name: Create the network 10.0.0.0/16
  docker_network:
    name: network-10.0.0.0_16
    ipam_config:
      - subnet: 10.0.0.0/16
        gateway: 10.0.0.1

- name: Start the container 'ubuntu_18.04' if it's not up
  docker_container:
    # The container 'ubuntu_18.04' should be existed and started.
    # If it doesn't exist then create it using ubuntu-sshd:18.04 image and start.
    name: ubuntu_18.04
    image: ubuntu-sshd:18.04
    published_ports: 127.0.0.1:22:22
    state: started

- name: Assign the ip 10.0.0.2 and connect the container to the network
  docker_container:
    name: ubuntu_18.04
    networks:
      - name: network-10.0.0.0_16
        ipv4_address: "10.0.0.2"
    state: started
    # Suppress DEPRECATION WARNING
    networks_cli_compatible: yes

$ ansible-playbook playbook.yml 
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'

PLAY [localhost] *********************************************************************************************************************************************

TASK [Gathering Facts] ***************************************************************************************************************************************
ok: [localhost]

TASK [container-net-setup : Create the network 10.0.0.0/16] **************************************************************************************************
changed: [localhost]

TASK [container-net-setup : Start the container 'ubuntu_18.04' if it's not up] *******************************************************************************
changed: [localhost]

TASK [container-net-setup : Assign the ip 10.0.0.2 and connect the container to the network] *****************************************************************
changed: [localhost]

PLAY RECAP ***************************************************************************************************************************************************
localhost                  : ok=4    changed=3    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

2. Install Nginx, configure it to serve static pages and dynamic pages via FCGI (python application)