Add swap memory with ansible - memory

Question

I'm working on a project where having swap memory on my servers is a needed to avoid some python long running processes to go out of memory and realized for the first time that my ubuntu vagrant boxes and AWS ubuntu instances didn't already have one set up.
In https://github.com/ansible/ansible/issues/5241 a possible built in solution was discussed but never implemented, so I'm guessing this should be a pretty common task to automatize.
How would you set up a file based swap memory with ansible in an idempotent way? What modules or variables does ansible provide help with this setup (like ansible_swaptotal_mb variable) ?

Answer 1

This is my current solution:
- name: Create swap file
command: dd if=/dev/zero of={{ swap_file_path }} bs=1024 count={{ swap_file_size_mb }}k
creates="{{ swap_file_path }}"
tags:
- swap.file.create
- name: Change swap file permissions
file: path="{{ swap_file_path }}"
owner=root
group=root
mode=0600
tags:
- swap.file.permissions
- name: "Check swap file type"
command: file {{ swap_file_path }}
register: swapfile
tags:
- swap.file.mkswap
- name: Make swap file
command: "sudo mkswap {{ swap_file_path }}"
when: swapfile.stdout.find('swap file') == -1
tags:
- swap.file.mkswap
- name: Write swap entry in fstab
mount: name=none
src={{ swap_file_path }}
fstype=swap
opts=sw
passno=0
dump=0
state=present
tags:
- swap.fstab
- name: Mount swap
command: "swapon {{ swap_file_path }}"
when: ansible_swaptotal_mb < 1
tags:
- swap.file.swapon

Answer 2

I tried the answer above but "Check swap file type" always came back as changed and therefore isn't idempotent which is encouraged as a best practice when writing Ansible tasks.
The role below has been tested on Ubuntu 14.04 Trusty and doesn't require gather_facts to be enabled.
- name: Set swap_file variable
set_fact:
swap_file: "{{swap_file_path}}"
tags:
- swap.set.file.path
- name: Check if swap file exists
stat:
path: "{{swap_file}}"
register: swap_file_check
tags:
- swap.file.check
- name: Create swap file
command: fallocate -l {{swap_file_size}} {{swap_file}}
when: not swap_file_check.stat.exists
tags:
- swap.file.create
- name: Change swap file permissions
file: path="{{swap_file}}"
owner=root
group=root
mode=0600
tags:
- swap.file.permissions
- name: Format swap file
sudo: yes
command: "mkswap {{swap_file}}"
when: not swap_file_check.stat.exists
tags:
- swap.file.mkswap
- name: Write swap entry in fstab
mount: name=none
src={{swap_file}}
fstype=swap
opts=sw
passno=0
dump=0
state=present
tags:
- swap.fstab
- name: Turn on swap
sudo: yes
command: swapon -a
when: not swap_file_check.stat.exists
tags:
- swap.turn.on
- name: Set swappiness
sudo: yes
sysctl:
name: vm.swappiness
value: "{{swappiness}}"
tags:
- swap.set.swappiness
As of Ansible 2.9, sudo declarations should be become:
- name: Set swap_file variable
set_fact:
swap_file: "{{swap_file_path}}"
tags:
- swap.set.file.path
- name: Check if swap file exists
stat:
path: "{{swap_file}}"
register: swap_file_check
tags:
- swap.file.check
- name: Create swap file
command: fallocate -l {{swap_file_size}} {{swap_file}}
when: not swap_file_check.stat.exists
tags:
- swap.file.create
- name: Change swap file permissions
file: path="{{swap_file}}"
owner=root
group=root
mode=0600
tags:
- swap.file.permissions
- name: Format swap file
become: yes
command: "mkswap {{swap_file}}"
when: not swap_file_check.stat.exists
tags:
- swap.file.mkswap
- name: Write swap entry in fstab
mount: name=none
src={{swap_file}}
fstype=swap
opts=sw
passno=0
dump=0
state=present
tags:
- swap.fstab
- name: Turn on swap
become: yes
command: swapon -a
when: not swap_file_check.stat.exists
tags:
- swap.turn.on
- name: Set swappiness
become: yes
sysctl:
name: vm.swappiness
value: "{{swappiness}}"
tags:
- swap.set.swappiness
Vars required:
swap_file_path: /swapfile
# Use any of the following suffixes
# c=1
# w=2
# b=512
# kB=1000
# K=1024
# MB=1000*1000
# M=1024*1024
# xM=M
# GB=1000*1000*1000
# G=1024*1024*1024
swap_file_size: 4G
swappiness: 1

Answer 3

I based my take on the great Ashley's answer (please upvote it!) and added the following extra features:
global flag to manage the swap or not,
allow changing the swap size,
allow disabling swap,
...plus these technical improvements:
full idempotency (only ok & skipping when nothing is changed, otherwise some changed),
use dd instead of fallocate for compatibility with XFS fs (see this answer for more info),
Limitations:
changes the existing swapfile works correctly only if you provide its path as swap_file_path.
Tested on Centos 7.7 with Ansible 2.9 and Rocky 8 with Ansible
4.8.0.
Requires using privilege escalation as many of the commands need to run as root. (The easiest way to do it is to add --become to ansible-playbook arguments or to set the appropriate value in your ansible.cfg).
Parameters:
swap_configure: true # or false
swap_enable: true # or false
swap_file_path: /swapfile
swap_file_size_mb: 4096
swappiness: 1
Code:
- name: Configure swap
when: swap_configure | bool
block:
- name: Check if swap file exists
stat:
path: "{{swap_file_path}}"
get_checksum: false
get_md5: false
register: swap_file_check
changed_when: false
- name: Set variable for existing swap file size
set_fact:
swap_file_existing_size_mb: "{{ (swap_file_check.stat.size / 1024 / 1024) | int }}"
when: swap_file_check.stat.exists
- name: Check if swap is on
shell: swapon --show | grep {{swap_file_path}}
register: swap_is_enabled
changed_when: false
failed_when: false
- name: Disable swap
command: swapoff {{swap_file_path}}
register: swap_disabled
when: >
swap_file_check.stat.exists
and 'rc' in swap_is_enabled and swap_is_enabled.rc == 0
and (not swap_enable or (swap_enable and swap_file_existing_size_mb != swap_file_size_mb))
- name: Delete the swap file
file:
path: "{{swap_file_path}}"
state: absent
when: not swap_enable
- name: Remove swap entry from fstab
mount:
name: none
src: "{{swap_file_path}}"
fstype: swap
opts: sw
passno: '0'
dump: '0'
state: present
when: not swap_enable
- name: Configure swap
when: swap_enable | bool
block:
- name: Create or change the size of swap file
command: dd if=/dev/zero of={{swap_file_path}} count={{swap_file_size_mb}} bs=1MiB
register: swap_file_created
when: >
not swap_file_check.stat.exists
or swap_file_existing_size_mb != swap_file_size_mb
- name: Change swap file permissions
file:
path: "{{swap_file_path}}"
mode: 0600
- name: Check if swap is formatted
shell: file {{swap_file_path}} | grep 'swap file'
register: swap_file_is_formatted
changed_when: false
failed_when: false
- name: Format swap file if it's not formatted
command: mkswap {{swap_file_path}}
when: >
('rc' in swap_file_is_formatted and swap_file_is_formatted.rc > 0)
or swap_file_created.changed
- name: Add swap entry to fstab
mount:
name: none
src: "{{swap_file_path}}"
fstype: swap
opts: sw
passno: '0'
dump: '0'
state: present
- name: Turn on swap
shell: swapon -a
# if swap was disabled from the start
# or has been disabled to change its params
when: >
('rc' in swap_is_enabled and swap_is_enabled.rc != 0)
or swap_disabled.changed
- name: Configure swappiness
sysctl:
name: vm.swappiness
value: "{{ swappiness|string }}"
state: present

Answer 4

I'm not able to reply to Greg Dubicki answer so I add my 2 cents here:
I think adding casting to int when doing calculation on swap_file_size_mb * 1024 * 1024 to transform it into swap_file_size_mb | int * 1024 * 1024 will make the code a bit smarter in case you want to use a fact to extract the final swap size based on the amount of RAM installed like:
swap_file_size_mb: "{{ ansible_memory_mb['real']['total'] * 2 }}"
else it will always resize the swap file even if the size it's the same.

Answer 5

Here is the ansible-swap playbook that I use to install 4GB (or whatever I configure group_vars for dd_bs_size_mb * swap_count) of swap space on new servers:
https://github.com/tribou/ansible-swap
I also added a function in my ~/.bash_profile to help with the task:
# Path to where you clone the repo
ANSIBLE_SWAP_PLAYBOOK=$HOME/dev/ansible-swap
install-swap ()
{
usage='Usage: install-swap HOST';
if [ $# -ne 1 ]; then
echo "$usage";
return 1;
fi;
ansible-playbook $ANSIBLE_SWAP_PLAYBOOK/ansible-swap/site.yml --extra-vars "target=$1"
}
Just make sure to add your HOST to your ansible inventory first.
Then it's just install-swap HOST.

Answer 6

Here is a preexisting role on Galaxy which achieves the same thing: https://galaxy.ansible.com/geerlingguy/swap

Answer 7

What works for me is to add 4Gib swap through the playbook.
Check this:
.