Task 'Disable swap' fails when there is no swap configured on a node

[neuliuyin]

Environment:

• OS (printf "$(uname -srm)\n$(cat /etc/os-release)\n"):
  Linux 3.10.0-1127.el7.x86_64 x86_64
  NAME="CentOS Linux"
  VERSION="7 (Core)"

• Version of Ansible (ansible --version):
  ansible 2.9.6

• Version of Python (python --version):
  python version = 3.7.3 (default, Aug 4 2020, 19:30:55) [Clang 11.0.3 (clang-1103.0.32.62)]

• Kubespray version (commit) (git rev-parse --short HEAD):
  kubespray-2.13.3

• Command used to invoke ansible:
  ansible-playbook -i contrib/inventory_builder/k8s_hosts.yaml cluster.yml --user centos -b --check

• Output of ansible run:
  fatal: [master1]: FAILED! => {"msg": "The conditional check 'swapon.stdout' failed. The error was: error while evaluating conditional (swapon.stdout): 'dict object' has no attribute 'stdout'\n\nThe error appears to be in '/Users/lyin/Downloads/kubespray-2.13.3/roles/kubernetes/preinstall/tasks/0010-swapoff.yml': line 16, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n changed_when: no\n- name: Disable swap\n ^ here\n"}

• Anything else do we need to know:

  [root@master1 ~]# free
                total        used        free      shared  buff/cache   available
  Mem:        1881860      108348     1553428       16884      220084     1612312
  Swap:             0           0           0
  [root@master1 ~]# swapon -s
  [root@master1 ~]#

[floryut]

@neuliuyin could you put the entire log ? and if possible add (between line 15 and 16)

        - debug:
                msg: "{{ swapon }}"

I'm trying to reproduce but can't seem to be able to have a commands without stdout attribute.

[neuliuyin]

@floryut here is debug output:

TASK [debug] ***********************************************************************************************************************************
ok: [master1] => {
    "msg": {
        "changed": false,
        "cmd": [
            "/sbin/swapon",
            "-s"
        ],
        "delta": "0:00:00.004486",
        "end": "2020-09-10 06:45:08.465100",
        "failed": false,
        "rc": 0,
        "start": "2020-09-10 06:45:08.460614",
        "stderr": "",
        "stderr_lines": [],
        "stdout": "",
        "stdout_lines": []
    }
}

[floryut]

Wahou... That's what I got..I really don't understand how the ansible task report the swapon as missing an stdout parameter as you clearly got one.

[neuliuyin]

Maybe check whether swapon.stdout is null or its length.

[EppO]

Maybe check whether swapon.stdout is null or its length.

shouldn't need it, the code is quite simple:

- name: check swap
  command: /sbin/swapon -s
  register: swapon
  changed_when: no

this takes the output of /sbin/swapon -s into the variable swapon in the object you pasted with the debug msg task. And it always runs (no when: attribute), hence it should get populated no matter what, with the stdout attribute.

- name: Disable swap
  command: /sbin/swapoff -a
  when: swapon.stdout

It's using the swapon object and extracts the stdout attribute from it. It works with your msg debug task but not that one, it's really weird. Are you sure you run your first cluster.yaml command with -b ? swapon is in /sbin, accessible only by root user. But it would fail at the swapon task I assume...

[neuliuyin-new]

@EppO I'm sure -b was there when the issue happened.

I checked again and found that the issue is caused by the --check flag.
When running in this mode, task check swap is somehow skipped and causes the exception in task Disable swap.

[floryut]

Interesting, will check that and maybe put a check_mode: no on the check swap as it's only a task for getting some value, it won't do any harm.

[floryut]

I've submit a PR, WDYT ?