Iterate over inventory group

[Laurent Goussard]

Hello,

I try to setup a cron task using ansible (indeed) on my db slave pool.
This cron task is supposed to stop the replication process, dump the database and restart replication.
Because the backup takes a little time, I don't want to init the cron task at the same time on all the db slaves and I don't want to stop all the slaves at the same times either.

My first idea was to set a different time while looping on the group.
But it's definitely not as trivial as it seems :

- name: database backup cron task
  cron: name="database backup" hour={{ item.key }} user="root" job="backup_db.sh" cron_file=database_backup
  with_dict: groups.mysql

The point is an inventory group is a list, not a dictionnary and I cannot find any simple way to convert a list to a dict (whereas it's easy to convert a dict as a list)
I also tried to use the group list instead, but I cannot figure out how I can get an iterator key.

Did I miss something ? Do you have any clue regarding my (not so complex imho) problem ?

[Dan Vaida]

to iterate over a hosts group you need with_items: groups['mysql'] instead of with_dict

[Laurent Goussard]

Thanks, but as I said, I tried to loop over the group list, but I cannot get any iteration key.

I try to loop over a hosts group and getting an index of the current iteration in order to set a cron task at midnight for the first host, 01am for the second, 02am for the third, etc...

[Dan Vaida]

Isn't it feasible for you to simply do

- hosts: mysql
  sudo: yes
  tasks:
    - cron: name="database backup" hour={{ hour }} user="root" job="backup_db.sh" cron_file=database_backup

and then in your host_vars/member_of_mysql_group, you would have 

hour: "01"

and so on?

[Matt Martz]

Take a look at with_indexed_items: 
http://docs.ansible.com/playbooks_loops.html#looping-over-a-list-with-an-index

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Matt Martz
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[Laurent Goussard]

That would be a fallback solution, but I'd prefer not to use group nor host vars for defining such iterator. That would lead on errors and that not very elegant, in my opinion..

[Laurent Goussard]

Thank you Matt !
That's definitely what I needed.

There is a lot of useful gems hidden in the footer or subnotes of the documentation !

Le mercredi 14 janvier 2015 13:31:56 UTC+1, Matt Martz a écrit :

Take a look at with_indexed_items: 
http://docs.ansible.com/playbooks_loops.html#looping-over-a-list-with-an-index

On Wednesday, January 14, 2015, Laurent Goussard <laur...@gmail.com> wrote:

Thanks, but as I said, I tried to loop over the group list, but I cannot get any iteration key.

I try to loop over a hosts group and getting an index of the current iteration in order to set a cron task at midnight for the first host, 01am for the second, 02am for the third, etc...

Le mardi 13 janvier 2015 20:47:22 UTC+1, Dan Vaida a écrit :

to iterate over a hosts group you need with_items: groups['mysql'] instead of with_dict

On Tuesday, 13 January 2015 09:41:07 UTC+1, Laurent Goussard wrote:

Hello,

I try to setup a cron task using ansible (indeed) on my db slave pool.
This cron task is supposed to stop the replication process, dump the database and restart replication.
Because the backup takes a little time, I don't want to init the cron task at the same time on all the db slaves and I don't want to stop all the slaves at the same times either.

My first idea was to set a different time while looping on the group.
But it's definitely not as trivial as it seems :

- name: database backup cron task
  cron: name="database backup" hour={{ item.key }} user="root" job="backup_db.sh" cron_file=database_backup
  with_dict: groups.mysql

The point is an inventory group is a list, not a dictionnary and I cannot find any simple way to convert a list to a dict (whereas it's easy to convert a dict as a list)
I also tried to use the group list instead, but I cannot figure out how I can get an iterator key.

Did I miss something ? Do you have any clue regarding my (not so complex imho) problem ?

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