#理解
changed_when
failed_when
become
become_user
ansible_become
ansible_become_user
static


#檢查group_vars中某組是否存在主機
- name: ensure only one monitoring host exists
  fail: msg="One, or no monitoring host may be specified."
  when: "groups.get(‘monitoring_servers‘, [])|length > 1"

#如果不定義值，那麽使用默認值
 
- name: set deploy dir if not presented
  set_fact: deploy_dir="/home/{{deploy_user}}/deploy"
  when: deploy_dir is not defined

#禁掉swap
- name: disable swap
  shell: "([ $(swapon -s | wc -l) -ge 1 ] && (swapoff -a && echo disable)) || echo already"
  ignore_errors: yes
  register: swapoff_result
  changed_when: 
 
"swapoff_result.stdout.strip() == ‘disable‘"

#當set_timezone定義，設置相應時區
- name: set timezone to {{timezone}}
  timezone: name={{ timezone }}
  when: set_timezone

#設置hostname
- name: set hostname by ip
  hostname: name=ip-{{ ansible_default_ipv4.address | replace(".","-") }}
  register: hostname_set
  when:
    
 
- set_hostname
    - "ansible_default_ipv4.address | replace(‘.‘,‘-‘) not in ansible_hostname"

#設置/etc/hosts
- name: inject hostname to hosts file
  lineinfile: dest=/etc/hosts line=‘127.0.0.1  ip-{{ ansible_default_ipv4.address | replace(\".\",\"-\") }}‘
  when: set_hostname

‘#修改文件中匹配到的某行
- name：modify centos irqbalance configuration file
  lineinfile:
    dest=/etc/default/irqbalance
    regexp=‘(?<!_)ONESHOT=‘
    line=‘ONESHOT=yes‘
  when:
    - tuning_irqbalance_value
    - centos_irq_config_file.stat.exists

#檢查umask
- name: get umask
  shell: umask
  register: umask
  changed_when: False

- name: does the system have a standard umask
  fail: ‘The umask of the system ({{ umask.stdout.strip() }}) prevents successful installation. We suggest a standard umask such as 0022.‘
  when: umask.stdout.strip()[-2:] not in (‘00‘, ‘02‘, ‘20‘, ‘22‘)

#根據facts值，檢查系統版本
- name: check system version
  fail:
    msg: "Red Hat Enterprise Linux/CentOS 6 is deprecated"
  when: "ansible_os_family == ‘RedHat‘ and ansible_distribution_major_version == ‘6"

#檢查文件掛載點
- name: detemine which mountpoint depoly dir exists on
  shell: "df {{ deploy_dir }} | tail -n1 | awk ‘{print $NF}‘"
  register: deploy_partition
  changed_when: False

#抓取log
- name: fetch pd log file
  fetch:
    src: "{{ log_dir }}/{{ inventory_hostname }}-pd.tar.gz"
    dest: "{{ fetch_tmp_dir }}/{{ inventory_hostname }}/"
    flat: yes
    validate_checksum: no
  when: "‘pd_servers‘ in group_names"

#下載tidb二進制
- name: download tidb binary
  get_url:
    url: "{{ item.url }}"
    dest: "{{ doenloads_dir }}/{{ item.name }}-{{ item.version }}.tar.gz"
    checksum: "{{ item.checksum | default(omit) }}"
    force: yes
    validate_certs: no
  register: get_url_result
  until: "‘OK‘ in get_url_result.msg or ‘file already exists‘ in get_url_result.msg"
  retries: 4
  delay: "{{ retry_stagger | random + 3 }}"
  with_items: "{{ tidb_packages }}"
  when: has_outband_network

#debug
- debug:
    msg: "run command on server: {{ disk_randread_iops.cmd }}"

一些ansible roles例子