Molecule failing randomly on apt update

[warsameSkew]

Hola! I'm unable to get a consist experience when using Molecule to test out roles.

For whatever reason, the same role passing today fails the next day by simply re-running it.

molecule 3.2.2 using python 3.8
ansible:2.10.4
delegated:3.2.2 from molecule

The only consistency is this failed task:

TASK [Update apt cache.] *******************************************************
fatal: [instance]: FAILED! => {"changed": false, "msg": "Failed to update apt cache: unknown reason"}

Login to the docker container and executing an apt update renders (which wasn't there initially)

root@instance:/# apt update
Err:1 http://archive.ubuntu.com/ubuntu focal InRelease                   
  Temporary failure resolving 'archive.ubuntu.com'
Err:2 http://security.ubuntu.com/ubuntu focal-security InRelease         
  Temporary failure resolving 'security.ubuntu.com'
0% [Connecting to archive.ubuntu.com]

Not sure what's happening here to cause this random error

[ghost]

Have you tried doing a task to clean the cache right before your apt update task? I remember this being an issue others have dealt with.

[warsameSkew]

Tried to clean apt, didn't resolve the issue:

molecule.yml

---
dependency:
  name: galaxy
driver:
  name: docker
lint: |
  set -e
  yamllint .
  ansible-lint
platforms:
  - name: instance
    image: "geerlingguy/docker-${MOLECULE_DISTRO:-ubuntu1804}-ansible:latest"
    command: ${MOLECULE_DOCKER_COMMAND:-""}
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
    privileged: true
    pre_build_image: true
provisioner:
  name: ansible
  playbooks:
    converge: ${MOLECULE_PLAYBOOK:-converge.yml}

converge,yml

---
- name: Converge
  hosts: all
  become: true

  pre_tasks:
    - name: Clean apt cache
      command: apt-get clean

    - name: Update apt cache
      apt:
        update_cache: yes

    - name: Install dependencies
      apt:
        name:
          - wget
          - unzip
        state: present

output:

PLAY [Converge] ****************************************************************

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

TASK [Clean apt cache] *********************************************************
[WARNING]: Consider using the apt module rather than running 'apt-get'.  If you
need to use command because apt is insufficient you can add 'warn: false' to
this command task or set 'command_warnings=False' in ansible.cfg to get rid of
this message.
changed: [instance]

TASK [Update apt cache] ********************************************************
fatal: [instance]: FAILED! => {"changed": false, "msg": "Failed to update apt cache: unknown reason"}

PLAY RECAP *********************************************************************
instance                   : ok=2    changed=1    unreachable=0    failed=1    skipped=0    rescued=0    ignored=0

[ghost]

Try this to clean the cache instead of using the command module:

- name: Remove useless packages from the cache
  apt:
    autoclean: yes

[decentral1se]

What @larmbuster said and also re: "Not sure what's happening here to cause this random error" you need to search up containers and DNS, you might have local issues.

[warsameSkew]

Issue resolved.

Cause: DNS

Fix

https://www.ricmedia.com/set-permanent-dns-nameservers-ubuntu-debian-resolv-conf/

Alternative Fix:

Pass dns_servers to container in molecule.yml like this.

molecule.yml

platforms:
  - name: instance
    image: "geerlingguy/docker-${MOLECULE_DISTRO:-ubuntu1804}-ansible:latest"
    command: ${MOLECULE_DOCKER_COMMAND:-""}
    volumes:
      - /sys/fs/cgroup:/sys/fs/cgroup:ro
    privileged: true
    pre_build_image: true
    dns_servers:
      - 8.8.8.8  # google's dns server, to pass your dns server see down below

Retrieve the DNS server you use with this command: nmcli dev show | grep 'IP4.DNS

Resources to understand why it happened:

https://docs.docker.com/config/containers/container-networking/#dns-services
https://man7.org/linux/man-pages/man5/resolv.conf.5.html
http://manpages.ubuntu.com/manpages/bionic/man8/systemd-resolved.service.8.html

Thank you team molecule for the replies, looking forward to using your product more!