87 lines
2.7 KiB
ReStructuredText
87 lines
2.7 KiB
ReStructuredText
=======
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Ansible
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=======
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Ansible configuration is described in detail in the `Ansible documentation
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<https://docs.ansible.com/ansible/latest/reference_appendices/config.html>`__.
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It is explained elsewhere in this guide how to configure Ansible for
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:ref:`Kayobe <configuration-kayobe-ansible>` and :ref:`Kolla Ansible
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<configuration-kolla-ansible-ansible>`.
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In this section we cover some options for tuning Ansible for performance and
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scale.
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SSH pipelining
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==============
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SSH pipelining is disabled in Ansible by default, but is generally safe to
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enable, and provides a reasonable performance improvement.
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.. code-block:: ini
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:caption: ``$KAYOBE_CONFIG_PATH/ansible.cfg``
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[ssh_connection]
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pipelining = True
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Forks
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=====
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By default Ansible executes tasks using a fairly conservative 5 process forks.
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This limits the parallelism that allows Ansible to scale. Most Ansible control
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hosts will be able to handle far more forks than this. You will need to
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experiment to find out the CPU, memory and IO limits of your machine.
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For example, to increase the number of forks to 20:
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.. code-block:: ini
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:caption: ``$KAYOBE_CONFIG_PATH/ansible.cfg``
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[defaults]
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forks = 20
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Fact caching
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============
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.. note::
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Fact caching will not work correctly in Kayobe prior to the Ussuri release.
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By default, Ansible gathers facts for each host at the beginning of every play,
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unless ``gather_facts`` is set to ``false``. With a large number of hosts this
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can result in a significant amount of time spent gathering facts.
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One way to improve this is through Ansible's support for `fact caching
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<https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#caching-facts>`__.
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In order to make this work with Kayobe, it is necessary to change Ansible's
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`gathering
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<https://docs.ansible.com/ansible/latest/reference_appendices/config.html#default-gathering>`__
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configuration option to ``smart``. Additionally, it is necessary to use
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separate fact caches for Kayobe and Kolla Ansible due to some of the facts
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(e.g. ``ansible_user_uid`` and ``ansible_python``) differing.
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Example
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-------
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In the following example we configure Kayobe and Kolla Ansible to use fact
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caching using the `jsonfile cache plugin
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<https://docs.ansible.com/ansible/latest/plugins/cache/jsonfile.html>`__.
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.. code-block:: ini
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:caption: ``$KAYOBE_CONFIG_PATH/ansible.cfg``
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[defaults]
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gathering = smart
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fact_caching = jsonfile
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fact_caching_connection = /tmp/kayobe-facts
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.. code-block:: ini
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:caption: ``$KAYOBE_CONFIG_PATH/kolla/ansible.cfg``
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[defaults]
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gathering = smart
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fact_caching = jsonfile
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fact_caching_connection = /tmp/kolla-ansible-facts
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You may also wish to set the expiration timeout for the cache via ``[defaults]
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fact_caching_timeout``.
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