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[stable-2.7] Add an example to serial usage (#48669)

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(cherry picked from commit b759862daa)

Co-authored-by: Toshio Kuratomi <a.badger@gmail.com>
This commit is contained in:
Toshio Kuratomi 2018-11-14 08:57:10 -08:00
parent 1dab508cd4
commit cef08640a4
1 changed files with 39 additions and 4 deletions
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43
docs/docsite/rst/user_guide/playbooks_delegation.rst
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@ -19,21 +19,55 @@ You'll also want to read up on :doc:`playbooks_reuse_roles`, as the 'pre_task' a
Be aware that certain tasks are impossible to delegate, i.e. `include`, `add_host`, `debug`, etc as they always execute on the controller. Be aware that certain tasks are impossible to delegate, i.e. `include`, `add_host`, `debug`, etc as they always execute on the controller.
.. _rolling_update_batch_size: .. _rolling_update_batch_size:
Rolling Update Batch Size Rolling Update Batch Size
````````````````````````` `````````````````````````
By default, Ansible will try to manage all of the machines referenced in a play in parallel. For a rolling update use case, you can define how many hosts Ansible should manage at a single time by using the ``serial`` keyword:: By default, Ansible will try to manage all of the machines referenced in a play in parallel. For a rolling update use case, you can define how many hosts Ansible should manage at a single time by using the ``serial`` keyword::
- name: test play - name: test play
hosts: webservers hosts: webservers
serial: 3 serial: 2
gather_facts: False
tasks:
- name: task one
comand: hostname
- name: task two
command: hostname
In the above example, if we had 4 hosts in the group 'webservers', 2
would complete the play completely before moving on to the next 2 hosts::
PLAY [webservers] ****************************************
TASK [task one] ******************************************
changed: [web2]
changed: [web1]
TASK [task two] ******************************************
changed: [web1]
changed: [web2]
PLAY [webservers] ****************************************
TASK [task one] ******************************************
changed: [web3]
changed: [web4]
TASK [task two] ******************************************
changed: [web3]
changed: [web4]
PLAY RECAP ***********************************************
web1 : ok=2 changed=2 unreachable=0 failed=0
web2 : ok=2 changed=2 unreachable=0 failed=0
web3 : ok=2 changed=2 unreachable=0 failed=0
web4 : ok=2 changed=2 unreachable=0 failed=0
In the above example, if we had 100 hosts, 3 hosts in the group 'webservers'
would complete the play completely before moving on to the next 3 hosts.
The ``serial`` keyword can also be specified as a percentage, which will be applied to the total number of hosts in a The ``serial`` keyword can also be specified as a percentage, which will be applied to the total number of hosts in a
play, in order to determine the number of hosts per pass:: play, in order to determine the number of hosts per pass::
@ -77,6 +111,7 @@ You can also mix and match the values::
.. note:: .. note::
No matter how small the percentage, the number of hosts per pass will always be 1 or greater. No matter how small the percentage, the number of hosts per pass will always be 1 or greater.
.. _maximum_failure_percentage: .. _maximum_failure_percentage:
Maximum Failure Percentage Maximum Failure Percentage