Nested loop with second loop depending on first item

[Guillaume Subiron]

Hi,

I'm trying to do a special kind of nesting loop, using the item of the
first loop in the second loop:

- name: Prepare OSDs
shell: ceph-deploy osd prepare {{ item[0] }}:{{ item[1] }}
with_nested:
- groups['ceph-ODSs']
- hostvars[item[0]]['disks']

I'm not sure if this is possible, but I can't find any workaround.

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Guillaume Subiron
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[Serge van Ginderachter]

Have a look at the with_subelements lookup plugin.

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[Guillaume Subiron]

Le 13/12/11 11:18, Serge van Ginderachter claviotta :

> Have a look at the with_subelements lookup plugin.

I know very well with_subelements, but in this case I'm not trying to
access a subelement in the first element, I'm trying to use the first
element to access an entry in an other dictionary.

I don't think with_subelements is well suited to this case. Do you
have an example ?

[Michael DeHaan]

Before we dive into a technical solution let me understand your use case and what you are modelling a bit better.

So groups['ceph-ODSs'] would be all machines in the ceph-ODSs group.

I'd probably just define a variable like "disks" on the group, but I'm unclear why that wouldn't work in your case.

I could probably understand more if I could see how "disks" differs between hosts.

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[Guillaume Subiron]

Le 13/12/11 08:05, Michael DeHaan claviotta :

> Before we dive into a technical solution let me understand your use case
> and what you are modelling a bit better.
>
> So groups['ceph-ODSs'] would be all machines in the ceph-ODSs group.

That's right.

>
> I'd probably just define a variable like "disks" on the group, but I'm
> unclear why that wouldn't work in your case.
>
> I could probably understand more if I could see how "disks" differs between
> hosts.

It's simple, my Ceph OSD (storage nodes) are all différents. Some
contains 2 hard drives (sdb, sdc), some contains 10 (sdb, sdc, sdd…).
"disks" is a list of hard drives, which is different from one host to
another. ex:

inventory

osd0
osd1

[ceph-OSDs]
osd0
osd1

host_vars/osd0

disks:
- sdb

host_vars/osd1

disks:
- sdb
- sdc

In my nested loop, I need to loop over the Ceph Storage nodes and
their hard drive. The hard drive list is an host variable (accessible
by hostvars[osd0]['disks'], for instance).

With the example above, I want my playbook to do :

ceph_deploy osd prepare osd0:sda
ceph_deploy osd prepare osd1:sda
ceph_deploy osd prepare osd1:sdb

[Michael DeHaan]

I think you probably want this:

- shell: echo {{ item.0 }}-{{item.1 }}

  with_together:

      - groups['ceph-OSDs']

      - disks

this will print for the first host

osd0-sdb

osd1-sdb

and for the second host

osd0-sdb

osd0-sdc

osd1-sdb

osd1-sdc

Let me know if that works for you and if I'm missing something we'll figure it out.

Thanks!

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[Guillaume Subiron]

Hum, this is not what I'm looking for, because my action is not
executed on the ceph-OSDs, but on another host (a centralized admin
node).
In this playbook, I'm not doing anything on the ceph-OSDs.

What I need to do (only on my admin node) is :

- shell: echo {{ item.0 }}-{{ item.1 }}

with_nested:
- groups['ceph-OSDs']
- the disks of the current item in the "groups['ceph-OSDs']" loop

I want it to print (on the admin host) :

osd0-sdb
osd1-sdb
osd1-sdc

Do you understand the problem ? I don't see any workaround. This is a
matter of syntax.


Le 13/12/11 08:24, Michael DeHaan claviotta :

[Guillaume Subiron]

After reading nested.py and realizing it would never do what I wanted,
I found a workaround.

On each ceph-ODSs :

- delegate_to: "{{ ceph-admin }}"
shell: echo {{ inventory_hostname }}-{{ item }}
with_items: disks



Anyway, thank you very much for your help :)


Le 13/12/11 14:53, Guillaume Subiron claviotta :

[Q]

Guillaume,

I have exactly the same problem with setting up OSD via ADM host and I was pulling my hair for 2 days.
I don't know how to thank you:)

[saisum...@gmail.com]

Hi I have seen ur resolutions in this page i.

I am also having the same issue with nested loops .

my scenario is nothing but the matrix multiplication of n*n

Can some one please suggest how to implement it using ansible loops along with adding conidition of count ++ and count --

[J Hawkesworth]

Hmm, would the cartesian lookup help you?

https://docs.ansible.com/ansible/latest/plugins/lookup/cartesian.html

[Brian Coca]

actually use the product filter instead of cartesian lookup



----------
Brian Coca