# Nested loop with second loop depending on first item **URL:** \ **Category:** Ansible Project\ **Created:** [December 11, 2013, 8:53am UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124 "2013-12-11T08:53:14Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Guillaume\_Subiron](https://avatars.discourse-cdn.com/v4/letter/g/c77e96/32.png) [@Guillaume\_Subiron](https://forum.ansible.com/u/Guillaume_Subiron)\ **Post date:** [December 11, 2013, 8:53am UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/1 "2013-12-11T08:53:14Z")
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. ---
**Author:** ![Serge\_van\_Ginderacht](https://avatars.discourse-cdn.com/v4/letter/s/b782af/32.png) [@Serge\_van\_Ginderacht](https://forum.ansible.com/u/Serge_van_Ginderacht)\ **Post date:** [December 11, 2013, 10:18am UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/2 "2013-12-11T10:18:28Z")
Have a look at the with\_subelements lookup plugin. ---
**Author:** ![Guillaume\_Subiron](https://avatars.discourse-cdn.com/v4/letter/g/c77e96/32.png) [@Guillaume\_Subiron](https://forum.ansible.com/u/Guillaume_Subiron)\ **Post date:** [December 11, 2013, 10:40am UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/3 "2013-12-11T10:40:08Z")
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 ? ---
**Author:** ![Michael\_DeHaan2](https://avatars.discourse-cdn.com/v4/letter/m/da6949/32.png) [@Michael\_DeHaan2](https://forum.ansible.com/u/Michael_DeHaan2)\ **Post date:** [December 11, 2013, 1:05pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/4 "2013-12-11T13:05:32Z")
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. ---
**Author:** ![Guillaume\_Subiron](https://avatars.discourse-cdn.com/v4/letter/g/c77e96/32.png) [@Guillaume\_Subiron](https://forum.ansible.com/u/Guillaume_Subiron)\ **Post date:** [December 11, 2013, 1:21pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/5 "2013-12-11T13:21:27Z")
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 ---
**Author:** ![Michael\_DeHaan2](https://avatars.discourse-cdn.com/v4/letter/m/da6949/32.png) [@Michael\_DeHaan2](https://forum.ansible.com/u/Michael_DeHaan2)\ **Post date:** [December 11, 2013, 1:24pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/6 "2013-12-11T13:24:40Z")
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! ---
**Author:** ![Guillaume\_Subiron](https://avatars.discourse-cdn.com/v4/letter/g/c77e96/32.png) [@Guillaume\_Subiron](https://forum.ansible.com/u/Guillaume_Subiron)\ **Post date:** [December 11, 2013, 1:53pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/7 "2013-12-11T13:53:10Z")
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 : ---
**Author:** ![Guillaume\_Subiron](https://avatars.discourse-cdn.com/v4/letter/g/c77e96/32.png) [@Guillaume\_Subiron](https://forum.ansible.com/u/Guillaume_Subiron)\ **Post date:** [December 11, 2013, 2:24pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/8 "2013-12-11T14:24:37Z")
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 : ---
**Author:** ![Q11](https://avatars.discourse-cdn.com/v4/letter/q/46a35a/32.png) [@Q11](https://forum.ansible.com/u/Q11)\ **Post date:** [June 9, 2017, 2:57pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/9 "2017-06-09T14:57:35Z")
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:) ---
**Author:** ![saisumanth443](https://avatars.discourse-cdn.com/v4/letter/s/898d66/32.png) [@saisumanth443](https://forum.ansible.com/u/saisumanth443)\ **Post date:** [November 14, 2018, 8:05am UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/10 "2018-11-14T08:05:31Z")
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 th\_\_e 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 – ---
**Author:** ![j.r.hawkesworth](https://avatars.discourse-cdn.com/v4/letter/j/a3d4f5/32.png) [@j.r.hawkesworth](https://forum.ansible.com/u/j.r.hawkesworth)\ **Post date:** [November 18, 2018, 10:29am UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/11 "2018-11-18T10:29:34Z")
Hmm, would the cartesian lookup help you? [https://docs.ansible.com/ansible/latest/plugins/lookup/cartesian.html](https://docs.ansible.com/ansible/latest/plugins/lookup/cartesian.html) ---
**Author:** ![system](https://us1.discourse-cdn.com/ansible/original/1X/1882d9a01da5d8996a862359b0913cc568a39b84.svg) [@system](https://forum.ansible.com/u/system)\ **Post date:** [November 21, 2018, 6:47pm UTC](https://forum.ansible.com/t/nested-loop-with-second-loop-depending-on-first-item/14124/12 "2018-11-21T18:47:33Z")
actually use the product filter instead of cartesian lookup