Method for checking the value of "serial"

[lucky numbersevun]

Hello,

I have a playbook that updates the kernel version on ceph cluster members.

Its important that we only do a single service at a time to prevent the OSD from trying to cope with a host when it reboots.

I want to verify that serial has been set to 1 and make sure that the playbook doesnt run otherwise.

The following code doesnt work, is there a way to do this?

++++

   - fail: msg="This playbook needs to be run with serial:1 so that only a single host is upgraded at a time"

     when: serial != "1"

++++

Thanks for your feedback/consideration/ideas/corrections-in-thinking/etc

best,

Lucky

[lucky numbersevun]

My apologies, I quickly typed that question out...to clarify...

> I have a playbook that updates the kernel version on ceph cluster members.

> Its important that we only do a single service at a time to prevent the OSD from trying to cope with a host when it reboots.

Its important that we only do a single SERVER at a time to prevent the cluster from incurring more than one down-server at a time.

:)

Anyhow...just wanted to clear and concise about it...

-Lucky

[Brian Coca]

well, the only place you can  set serial is on the play, that alone should ensure it.

but for the paranoid, you can use the play_hosts variable to either check if it is a list lenght of 1 or that the only item inside it is inventory_hostname.

--

Brian Coca

[Luca Menegus]

I think you could leverage the play_hosts var which contains the list of the hosts involved in the current play by asserting that its length is equal to 1 (a play start with hosts and tasks declaration, that is at the same level where you set the serial attr).

Bye,

 luca

PS: a little utility to dump ansible variables (Unfortunately I can't remember where I copied it from so I can't credit the author)

- template: src=debug_all_vars.j2 dest=/tmp/ansible.all.vars.debug

debug_all_vars.j2:

Module Variables ("vars"):

--------------------------------
{{ vars | to_nice_json }}

Environment Variables ("environment"):
--------------------------------
{{ environment | to_nice_json }}

GROUP NAMES Variables ("group_names"):
--------------------------------
{{ group_names | to_nice_json }}

GROUPS Variables ("groups"):
--------------------------------
{{ groups | to_nice_json }}

Luca

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[lucky numbersevun]

This worked.

[..snip..]

  tasks:

   - debug:  msg="The system {{ inventory_hostname }} will now be upgraded."

   - debug:  msg="The value of play_hosts is {{ play_hosts }}."

# This ensures that we dont proceed unless we're really only acting on a single host, for sure!

# Another option would be to refactor this playbook to accept a hostname/string as a target

# Another option would be to pass in --limit 'somehost' when running the playbook

   - assert: { that: "play_hosts | length == 1" }

#   - debug: msg="The variable play_hosts is length of 1, which means that only a single host will be upgraded at a time, proceeding with upgrade to {{ inventory_hostname }}"

[..snip..]

Thanks for the idea!

Lucky