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Large deployments of K8s========================
For a large scaled deployments, consider the following configuration changes:
* Tune [ansible settings](https://docs.ansible.com/ansible/latest/intro_configuration.html) for `forks` and `timeout` vars to fit large numbers of nodes being deployed.
* Override containers' `foo_image_repo` vars to point to intranet registry.
* Override the ``download_run_once: true`` and/or ``download_localhost: true``. See download modes for details.
* Adjust the `retry_stagger` global var as appropriate. It should provide sane load on a delegate (the first K8s control plane node) then retrying failed push or download operations.
* Tune parameters for DNS related applications Those are ``dns_replicas``, ``dns_cpu_limit``, ``dns_cpu_requests``, ``dns_memory_limit``, ``dns_memory_requests``. Please note that limits must always be greater than or equal to requests.
* Tune CPU/memory limits and requests. Those are located in roles' defaults and named like ``foo_memory_limit``, ``foo_memory_requests`` and ``foo_cpu_limit``, ``foo_cpu_requests``. Note that 'Mi' memory units for K8s will be submitted as 'M', if applied for ``docker run``, and cpu K8s units will end up with the 'm' skipped for docker as well. This is required as docker does not understand k8s units well.
* Tune ``kubelet_status_update_frequency`` to increase reliability of kubelet. ``kube_controller_node_monitor_grace_period``, ``kube_controller_node_monitor_period``, ``kube_apiserver_pod_eviction_not_ready_timeout_seconds`` & ``kube_apiserver_pod_eviction_unreachable_timeout_seconds`` for better Kubernetes reliability. Check out [Kubernetes Reliability](/docs/kubernetes-reliability.md)
* Tune network prefix sizes. Those are ``kube_network_node_prefix``, ``kube_service_addresses`` and ``kube_pods_subnet``.
* Add calico_rr nodes if you are deploying with Calico or Canal. Nodes recover from host/network interruption much quicker with calico_rr.
* Check out the [Inventory](/docs/getting-started.md#building-your-own-inventory) section of the Getting started guide for tips on creating a large scale Ansible inventory.
* Override the ``etcd_events_cluster_setup: true`` store events in a separate dedicated etcd instance.
For example, when deploying 200 nodes, you may want to run ansible with``--forks=50``, ``--timeout=600`` and define the ``retry_stagger: 60``.
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