Ansible “when variable == true” not behaving as expected

问题

I have the following tasks in a playbook I'm writing (results listed next to the debug statement in <>):

  - debug: var=nrpe_installed.stat.exists <true>
  - debug: var=force_install <true>
  - debug: var=plugins_installed.stat.exists <true>

  - name: Run the prep 
    include: prep.yml
    when: (nrpe_installed.stat.exists == false or plugins_installed.stat.exists == true or force_install == true)
    tags: ['prep']

  - debug: var=nrpe_installed.stat.exists <true>
  - debug: var=force_install <true>
  - debug: var=force_nrpe_install <false>

  - name: Install NRPE
    include: install-nrpe.yml
    when: (nrpe_installed.stat.exists == false or force_install == true or force_nrpe_install == true)
    tags: ['install_nrpe']
    vars:
      nrpe_url: 'http://url.goes.here'
      nrpe_md5: 3921ddc598312983f604541784b35a50
      nrpe_version: 2.15
      nrpe_artifact: nrpe-{{ nrpe_version }}.tar.gz
      nagios_ip: {{ nagios_ip }}
      config_dir: /home/ansible/config/

And I'm running it with the following command:

ansible-playbook install.yml -i $invFile --extra-vars="hosts=webservers force_install=True"

The first include runs, but the second skips with this output:

 skipping: [server1] => {"changed": false, "skip_reason": "Conditional check failed", "skipped": true}

I'm under the impression that the conditional check should pass for all of them as force_install == true evaluates to true which should make the whole when evaluate to true (since it's a series of 'OR's).

How do I get the when to run when the variables are set appropriately?

Edit:

Changing the second when for the Install NRPE include to the following works, but doesn't explain why the other one, Run the prep runs appropriately:

Working:

when: (not nrpe_installed.stat.exists or force_install or force_nrpe_install)

Also working:

when: (nrpe_installed.stat.exists == false or plugins_installed.stat.exists == true or force_install == true)

Not working:

when: (nrpe_installed.stat.exists == false or force_install == true or force_nrpe_install == true)

The truncated (duplicates removed) output of that particular section of the play is:

TASK [debug] *******************************************************************
ok: [server2] => {
    "nrpe_installed.stat.exists": true
}

TASK [debug] *******************************************************************
ok: [server2] => {
    "plugins_installed.stat.exists": true
}

TASK [debug] *******************************************************************
ok: [server2] => {
    "force_install": true
}

TASK [Run the prep] ************************************************************
included: /tasks/nrpe-install/prep.yml for server2, server3, server4, server5, server6, server7

TASK [Prep and configure for installation | Install yum packages] **************
ok: [server6] => (item=[u'gcc', u'glibc', u'glibc-common', u'gd', u'gd-devel', u'make', u'net-snmp', u'openssl-devel', u'unzip', u'tar', u'gzip', u'xinetd']) => {"changed": false, "item": ["gcc", "glibc", "glibc-common", "gd", "gd-devel", "make", "net-snmp", "openssl-devel", "unzip", "tar", "gzip", "xinetd"], "msg": "", "rc": 0, "results": ["gcc-4.1.2-55.el5.x86_64 providing gcc is already installed", "glibc-2.5-123.el5_11.3.i686 providing glibc is already installed", "glibc-common-2.5-123.el5_11.3.x86_64 providing glibc-common is already installed", "gd-2.0.33-9.4.el5_4.2.x86_64 providing gd is already installed", "gd-devel-2.0.33-9.4.el5_4.2.i386 providing gd-devel is already installed", "make-3.81-3.el5.x86_64 providing make is already installed", "net-snmp-5.3.2.2-20.el5.x86_64 providing net-snmp is already installed", "openssl-devel-0.9.8e-40.el5_11.x86_64 providing openssl-devel is already installed", "unzip-5.52-3.el5.x86_64 providing unzip is already installed", "tar-1.15.1-32.el5_8.x86_64 providing tar is already installed", "gzip-1.3.5-13.el5.centos.x86_64 providing gzip is already installed", "xinetd-2.3.14-20.el5_10.x86_64 providing xinetd is already installed"]}

TASK [Prep and configure for installation | Make nagios group] *****************
ok: [server2] => {"changed": false, "gid": 20002, "name": "nagios", "state": "present", "system": false}

TASK [Prep and configure for installation | Make nagios user] ******************
ok: [server6] => {"append": false, "changed": false, "comment": "User for Nagios NRPE", "group": 20002, "home": "/home/nagios", "move_home": false, "name": "nagios", "shell": "/bin/bash", "state": "present", "uid": 20002}

TASK [debug] *******************************************************************
ok: [server2] => {
    "nrpe_installed.stat.exists": true
}

TASK [debug] *******************************************************************
ok: [server2] => {
    "force_install": true
}

TASK [debug] *******************************************************************
ok: [server2] => {
    "force_nrpe_install": false
}

TASK [Install NRPE] ************************************************************
skipping: [server2] => {"changed": false, "skip_reason": "Conditional check failed", "skipped": true}

回答1:

You need to convert the variable to a boolean:

force_install|bool == true

I don't claim I understand the logic behind it. In python any non-empty string should be truthy. But when directly used in a condition it evaluates to false.

The bool filter then again interprets the strings "true" and "yes" (case-insensitive) as true. Any other string is false.

You might want to also set a default value in case force_install is not defined, since it would result into an undefined variable error:

force_install|default(false)|bool == true

回答2:

Yeah... certainly requires testing. I recommend

| bool is good unless you expect undefined vars
var is defined and (var | bool) if you expect undefined vars

default(False) is OK as long and you are happy that these are true if the input is not parsed from YAML. I.e. variables defined through --extra_vars CLI parameter are strings.

 "false"
 "null"
 "defined string"

Hope this helps:

#!/usr/bin/env ansible-playbook
---
- name: Test truthiness
  hosts: localhost
  gather_facts: False
  vars:
    truthy_vars:
    # TRUE
    - True
    - 1
    - "true"
    # FALSE
    - "false"
    - null
    - False
    - 0
    # ERROR (invalid sytax error stops the loop of the first of these)
    - "null"
    - "defined string"
    # ERROR
    # truthy_var_undefined
    # FALSE
    truthy_var_defined:
  tasks:
  - name: Test truthy
    debug:
      msg: "is truthy"
    ignore_errors: True # beware, the loo
    when: item
    loop: "{{ truthy_vars }}"
    loop_control:
      label: Test {{ item }}
  - name: truthy_var_undefined
    debug:
    when: truthy_var_undefined
    ignore_errors: true
  - name: truthy_var_defined
    debug:
    when: truthy_var_defined

- name: Test | default(False)
  hosts: localhost
  gather_facts: False
  vars:
    default_pipe_vars:
    # TRUE
    - True
    - 1
    - "true"
    # beware these:
    - "false"
    - "null"
    - "defined string" 
    # FALSE
    - null
    - False
    - 0
    # FALSE
    # default_pipe_undefined
    # FALSE
    default_pipe_defined:
  tasks:
  - name: Test | default(False)
    debug:
      msg: "is not | default(False)"
    when: item | default(False)
    loop: "{{ default_pipe_vars }}"
    loop_control:
      label: Test {{ item }}
  - name: default_pipe_undefined | default(False)
    debug:
    when: default_pipe_undefined | default(False)
  - name: default_pipe_defined | default(False)
    debug:
    when: default_pipe_defined | default(False)

- name: Test | bool
  hosts: localhost
  gather_facts: False
  vars:
    bool_vars:
    # TRUE
    - True
    - 1
    - "true"
    # FALSE
    - "defined string"
    - "null"
    - "false"
    - null
    - False
    - 0
    # ERROR
    # bool_undefined
    # FALSE
    bool_defined:
  tasks:
  - name: Test bool parsing
    debug:
      msg: "parsed as true booleans"
    when: item | bool
    loop: "{{ bool_vars }}"
    loop_control:
      label: Test {{ item }}
  - name: bool_undefined | bool
    debug:
    when: bool_undefined | bool
    ignore_errors: true
  - name: bool_defined var | bool
    debug:
    when: bool_defined | bool


- name: Test is defined and | bool
  hosts: localhost
  gather_facts: False
  vars:
    defined_bool_vars:
    # TRUE
    - True
    - 1
    - "true"
    # FALSE
    - "defined string"
    - "null"
    - "false"
    - null
    - False
    - 0
    # FALSE
    # defined_bool_undefined
    # FALSE
    defined_bool_defined:
  tasks:
  - name: Test bool parsing
    debug:
      msg: "parsed as true booleans"
    when:
    - item is defined
    - item | bool
    loop: "{{ defined_bool_vars }}"
    loop_control:
      label: Test {{ item }}
  - name: defined_bool_undefined | bool
    debug:
    when:
    - defined_bool_undefined is defined
    - defined_bool_undefined | bool
    ignore_errors: true
  - name: defined_bool_defined var | bool
    debug:
    when:
    - defined_bool_defined is defined
    - defined_bool_defined | bool

https://gist.github.com/kcd83/4ea23d201c271b58f1c4ef7844408657

来源：https://stackoverflow.com/questions/47881789/what-causes-ansible-to-evaluate-false-and-true-as-true

标签

ansible

ansible-playbook