Ansible regex with assert operator

Question

I have the following playbook that is trying to assert that a user prompt variable of NX-OS image equals the ansible_net_image captured from a Nexus switch. This is driving me crazy as to the correct format for the test condition.

---
- name: Upgrade NX-OS on switch with pre-checks to load image as required
 hosts: nexus-7000
 gather_facts: no
 vars_prompt:
 - name: NX_OS_Upgrade_Version
 prompt: "Please enter NX-OS version to upgrade too - ensure that the filename is as used by boot variable"
 private: no
 ##############################################################################
 ## Start of task execution
 ##############################################################################
 tasks:
 - name: Gather IOS configuration and software facts from switches
 nxos_facts:
 gather_subset: "!hardware"
################################################################################
## Display running image version to terminal
################################################################################
 - debug:
 msg: "{{ NX_OS_Upgrade_Version }}"
 - assert:
 that:
 - "ansible_net_image | regex:/^bootflash:\\/\\/\\/(.*) == NX_OS_Upgrade_Version"

Upon execution this error is displayed.

fatal: [switcha]: FAILED! => {"msg": "The conditional check 'ansible_net_image | regex:/^bootflash:\/\/\/(.) == NX_OS_Upgrade_Version' failed. The error was: template error while templating string: expected token 'end of statement block', got '/'. String: {% if ansible_net_image | regex:/^bootflash:\/\/\/(.) == NX_OS_Upgrade_Version %} True {% else %} False {% endif %}"} fatal: [switchb]: FAILED! => {"msg": "The conditional check 'ansible_net_image | regex:/^bootflash:\/\/\/(.) == NX_OS_Upgrade_Version' failed. The error was: template error while templating string: expected token 'end of statement block', got '/'. String: {% if ansible_net_image | regex:/^bootflash:\/\/\/(.) == NX_OS_Upgrade_Version %} True {% else %} False {% endif %}"}

The regex has been tested, but I am struggling to get the correct syntax for the Ansible play.

It would be great if someone could show me what I have got wrong.

Answer 1

Update

Q: "Check the version, copy a new image, and upgrade if required."

A: You can test the version. See Comparing versions. For example, given the current image for testing

 ansible_net_image: bootflash:///n5000-uk9-kickstart.5.1.3.N2.1b.bin

Get the version. Declare the variable

 ani_version: "{{ ansible_net_image|
 splitext|first|
 split('.', 1)|last }}"

gives

 ani_version: 5.1.3.N2.1b

Then test the version. In your question, you try to find out whether the versions are equal or not. This can be achieved by the comparison '==' below

 - assert:
 that: ani_version is version(NX_OS_Upgrade_Version, '==')
 success_msg: "Image is version {{ NX_OS_Upgrade_Version }}"
 fail_msg: "Image is NOT version {{ NX_OS_Upgrade_Version }}"

But, to check whether the image is newer or not you might want to use the comparison '<'

 - assert:
 that: ani_version is version(NX_OS_Upgrade_Version, '<')
 success_msg: "Image is newer version {{ NX_OS_Upgrade_Version }}"
 fail_msg: "Image is not newer version {{ NX_OS_Upgrade_Version }}"

---

Example of a complete playbook for testing

shell> cat pb.yml
- hosts: localhost
 vars:
 ani_version: "{{ ansible_net_image|
 splitext|first|
 split('.', 1)|last }}"
 vars_prompt:
 - name: NX_OS_Upgrade_Version
 prompt: Please enter NX-OS version to upgrade to
 private: no
 tasks:
 - name: Gather IOS configuration and software facts from switches
 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 # For testing use *set_fact* instead of *nxos_facts*
 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 # nxos_facts:
 # gather_subset: "!hardware"
 set_fact:
 ansible_net_image: bootflash:///n5000-uk9-kickstart.5.1.3.N2.1b.bin
 - debug:
 msg: |
 ani_version: {{ ani_version }}
 NX_OS_Upgrade_Version: {{ NX_OS_Upgrade_Version }}
 - assert:
 # that: ani_version is version(NX_OS_Upgrade_Version, '==')
 # success_msg: "Image is version {{ NX_OS_Upgrade_Version }}"
 # fail_msg: "Image is NOT version {{ NX_OS_Upgrade_Version }}"
 that: ani_version is version(NX_OS_Upgrade_Version, '<')
 success_msg: "Image is newer version {{ NX_OS_Upgrade_Version }}"
 fail_msg: "Image is not newer version {{ NX_OS_Upgrade_Version }}"
 - debug:
 msg: Copy and upgrade new image.

Copy and upgrade the new image

shell> ansible-playbook pb.yml
Please enter NX-OS version to upgrade to: 5.1.3.N2.1c
PLAY [localhost] ******************************************************************************
TASK [Gather IOS configuration and software facts from switches] ******************************
ok: [localhost]
TASK [debug] **********************************************************************************
ok: [localhost] => 
 msg: |-
 ani_version: 5.1.3.N2.1b
 NX_OS_Upgrade_Version: 5.1.3.N2.1c
TASK [assert] *********************************************************************************
ok: [localhost] => changed=false 
 msg: Image is newer version 5.1.3.N2.1c
TASK [debug] **********************************************************************************
ok: [localhost] => 
 msg: Copy and upgrade new image.
PLAY RECAP ************************************************************************************
localhost: ok=4 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0

Fails if the image is not newer

shell> ansible-playbook pb.yml
Please enter NX-OS version to upgrade to: 5.1.3.N2.1b
PLAY [localhost] ******************************************************************************
TASK [Gather IOS configuration and software facts from switches] ******************************
ok: [localhost]
TASK [debug] **********************************************************************************
ok: [localhost] => 
 msg: |-
 ani_version: 5.1.3.N2.1b
 NX_OS_Upgrade_Version: 5.1.3.N2.1b
TASK [assert] *********************************************************************************
fatal: [localhost]: FAILED! => changed=false 
 assertion: ani_version is version(NX_OS_Upgrade_Version, '<')
 evaluated_to: false
 msg: Image is not newer version 5.1.3.N2.1b
PLAY RECAP ************************************************************************************
localhost: ok=2 changed=0 unreachable=0 failed=1 skipped=0 rescued=0 ignored=0

---

Origin

• Use 7.3.2. Single-Quoted Style to create regex.
• See Testing strings.

For example,

- hosts: localhost
 vars:
 ansible_net_image: 'bootflash:///n5000-uk9-kickstart.5.1.3.N2.1b.bin'
 NX_OS_Upgrade_Version1: 'n5000-uk9-kickstart.5.1.3.N2.1b'
 my_regex1: '^bootflash:///{{ NX_OS_Upgrade_Version1 }}.bin'
 NX_OS_Upgrade_Version2: 'n5000-uk9-kickstart.5.1.4.N2.1b'
 my_regex2: '^bootflash:///{{ NX_OS_Upgrade_Version2 }}.bin'
 tasks:
 - assert:
 that: ansible_net_image is match(my_regex1)
 success_msg: "Image is version {{ NX_OS_Upgrade_Version1 }}"
 fail_msg: "Image is NOT version {{ NX_OS_Upgrade_Version1 }}"
 - assert:
 that: ansible_net_image is match(my_regex2)
 success_msg: "Image is version {{ NX_OS_Upgrade_Version2 }}"
 fail_msg: "Image is NOT version {{ NX_OS_Upgrade_Version2 }}"

gives (abridged)

TASK [assert] *************************************************************
ok: [localhost] => changed=false 
 msg: Image is version n5000-uk9-kickstart.5.1.3.N2.1b
TASK [assert] *************************************************************
fatal: [localhost]: FAILED! => changed=false 
 assertion: ansible_net_image is match(my_regex2)
 evaluated_to: false
 msg: Image is NOT version n5000-uk9-kickstart.5.1.4.N2.1b

• MikefNZ: Hi Vladimir for your response. This works but is there a way to achieve the same using the vars_prompt for user input and the nxos_facts: ansible_net_image variable? I don't want to hard code the variables every time the play is run against switches with different versions. The intent is to check the version and copy a new image and upgrade if required.