Add swap memory with ansible

问题:

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) ?

回答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

回答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

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

回答3:

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.