diff options
| -rw-r--r-- | ansible/gather-facts.yml | 2 | ||||
| -rw-r--r-- | ansible/group_vars/all.yml | 6 | ||||
| -rw-r--r-- | doc/source/user/ansible-tuning.rst | 41 | ||||
| -rw-r--r-- | etc/kolla/globals.yml | 12 | ||||
| -rw-r--r-- | releasenotes/notes/delegate-facts-hosts-a3c8bd588c805ffa.yaml | 6 |
5 files changed, 63 insertions, 4 deletions
diff --git a/ansible/gather-facts.yml b/ansible/gather-facts.yml index a30c7f4ed..468b5ae69 100644 --- a/ansible/gather-facts.yml +++ b/ansible/gather-facts.yml @@ -44,7 +44,7 @@ batch_size: "{{ ansible_play_batch | length }}" # Use a python list slice to divide the group up. # Syntax: [<start index>:<end index>:<step size>] - delegate_hosts: "{{ groups['all'][batch_index | int::batch_size | int] }}" + delegate_hosts: "{{ kolla_ansible_delegate_facts_hosts[batch_index | int::batch_size | int] }}" tasks: - name: Gather facts setup: diff --git a/ansible/group_vars/all.yml b/ansible/group_vars/all.yml index 7ee3f0b8f..4e1091414 100644 --- a/ansible/group_vars/all.yml +++ b/ansible/group_vars/all.yml @@ -36,6 +36,12 @@ kolla_ansible_setup_filter: "{{ omit }}" # By default, we do not provide a gather subset. kolla_ansible_setup_gather_subset: "{{ omit }}" +# This variable determines which hosts require facts when using --limit. Facts +# will be gathered using delegation for hosts in this list that are not +# included in the limit. +# By default, this list includes all hosts. +kolla_ansible_delegate_facts_hosts: "{{ groups['all'] }}" + ################### # Kolla options ################### diff --git a/doc/source/user/ansible-tuning.rst b/doc/source/user/ansible-tuning.rst index aa8db1cd2..dca711e9e 100644 --- a/doc/source/user/ansible-tuning.rst +++ b/doc/source/user/ansible-tuning.rst @@ -160,3 +160,44 @@ A max fail percentage may be set for specific services using kolla_max_fail_percentage: 50 nova_max_fail_percentage: 25 + +Delegated fact gathering +------------------------ + +When Kolla Ansible is executed with a ``--limit`` argument, the scope of an +operation is limited to the hosts in the limit. For example: + +.. code-block:: console + + kolla-ansible deploy --limit control + +Due to the nature of configuring clustered software services, there are cases +where we need to know information about other hosts. Most often this is related +to their hostname or network addresses. To make this work, Kolla Ansible +gathers facts for hosts outside of the limit using `delegated fact gathering +<https://docs.ansible.com/ansible/latest/playbook_guide/playbooks_delegation.html#delegating-facts>`__. + +By default, Kolla Ansible gathers facts for all hosts. Because delegated facts +are gathered serially in batches by the active hosts, this can take a long time +when there are not many hosts in the limit. If you know that facts are not +required for all hosts, it is possible to reduce the set of hosts eligible for +delegated fact gathering by setting ``kolla_ansible_delegate_facts_hosts`` to a +list of hosts. This may be done permanently in ``globals.yml`` or temporarily +for the duration of a command using the ``-e`` argument. + +The exact requirements will depend upon configuration and inventory, but here +are some rules of thumb: + +* Facts are typically required for all controllers, regardless of which hosts + are in the limit. This is due to references to RabbitMQ and Memcache + connection strings etc. +* Prometheus server requires facts for all other hosts to generate scrape + configs for node exporter, cAdvisor, etc. Specifically it uses the IP address + of the API interface. This may be avoided by hard-coding + ``prometheus_target_address`` in the inventory for each host. +* Configuration of ``/etc/hosts`` during the ``bootstrap-servers`` command + requires facts for all other hosts. Specifically it uses the IP address of + the API interface, and the ``hostname`` and ``nodename`` facts. +* Noting the above exceptions, compute nodes are fairly independent. Other + hosts do not need to know their facts, and they do not need to know other + hosts' facts. diff --git a/etc/kolla/globals.yml b/etc/kolla/globals.yml index 2afc0a155..88d9ce750 100644 --- a/etc/kolla/globals.yml +++ b/etc/kolla/globals.yml @@ -5,6 +5,9 @@ # commented parameters are shown here, To override the default value uncomment # the parameter and change its value. +# Dummy variable to allow Ansible to accept this file. +workaround_ansible_issue_8743: yes + ################### # Ansible options ################### @@ -21,15 +24,18 @@ # By default, we do not provide a gather subset. #kolla_ansible_setup_gather_subset: "{{ omit }}" -# Dummy variable to allow Ansible to accept this file. -workaround_ansible_issue_8743: yes - # This variable may be used to set the maximum failure percentage for all # plays. More fine-grained control is possible via per-service variables, e.g. # nova_max_fail_percentage. The default behaviour is to set a max fail # percentage of 100, which is equivalent to not setting it. #kolla_max_fail_percentage: +# This variable determines which hosts require facts when using --limit. Facts +# will be gathered using delegation for hosts in this list that are not +# included in the limit. +# By default, this list includes all hosts. +#kolla_ansible_delegate_facts_hosts: "{{ groups['all'] }}" + ############### # Kolla options ############### diff --git a/releasenotes/notes/delegate-facts-hosts-a3c8bd588c805ffa.yaml b/releasenotes/notes/delegate-facts-hosts-a3c8bd588c805ffa.yaml new file mode 100644 index 000000000..08f712ee2 --- /dev/null +++ b/releasenotes/notes/delegate-facts-hosts-a3c8bd588c805ffa.yaml @@ -0,0 +1,6 @@ +--- +features: + - | + Adds a new variable, ``kolla_ansible_delegate_facts_hosts``, that may be + used to control which hosts require facts when using ``--limit``. Its + default value is ``groups['all']``. |