Ansible - Looping blocks
I needed to do a loop inside a full block in Ansible, and I discovered that it was not possible to do something like this:
- name: this is a block
block:
- name: task one from the block, loop {item}
ansible.builtin.debug:
msg: "This is a block, indeed. Block: {item}."
- name: task two from the block, loop {item}
ansible.builtin.debug:
msg: "This is a block, indeed. Block: {item}."
loop:
- "one"
- "two"
Yep, this won’t work and will give me an error because the loop clause can’t be used inside a block. What I should do?
The solution that I found was to create a separate tasks file, and use a loop with ansible.builtin.include_tasks.
This tasks file would be equivalent to a block, but inside it we’ll have just a set of tasks instead of a block.
An example which works:
- File
main.yml
---
- name: setup VMs
ansible.builtin.include_tasks:
file: setup_vms.yml
loop:
- "webserver"
- "database"
- "appserver"
loop_control:
loop_var: vm
- File
setup_vms.yml
---
- name: VM {{ vm }} - create
ansible.builtin.command:
cmd: vm create {{ vm }}
- name: VM {{ vm }} - configure
ansible.builtin.command:
cmd: vm config {{ vm }} set {{ idx }} {{ item }}
loop:
- "disk"
- "memory"
- "network"
loop_control:
index_var: idx
Now this loop will “run” three times, doing the two tasks inside setup_vms.yml, with the values from the loop. Also, notice that:
-
In
main.yml, I used theloop_controlandloop_varto specify that in the other file, I can reference the value of the loop item asvm, instead of the defaultitem. -
I also used a loop inside the loop, which you can see in the file
setup_vms.yml. This was possible mainly because I associated the first loop with the variablevm, and the second loop will use the default{{ item }}. -
The
loop_controlandindex_varin thesetup_vms.ymlwas used to define a variable to the index of each loop’s item. In this case,diskas index0,memoryas1, andnetworkas2. I used this index number in the command (also note that we can’t use this index variable in the task’s name).
As a result, 12 tasks were executed:
VM webserver - create
- vm create webserver
VM webserver - configure
- vm config webserver set 0 disk
VM webserver - configure
- vm config webserver set 1 memory
VM webserver - configure
- vm config webserver set 2 network
VM database - create
- vm create database
VM database - configure
- vm config database set 0 disk
VM database - configure
- vm config database set 1 memory
VM database - configure
- vm config database set 2 network
VM appserver - create
- vm create appserver
VM appserver - configure
- vm config appserver set 0 disk
VM appserver - configure
- vm config appserver set 1 memory
VM appserver - configure
- vm config appserver set 2 network