c12s-kubespray/docs/large-deployments.md
Sergii Golovatiuk c07d60bc90 Kubernetes Reliability Improvements
- Exclude kubelet CPU/RAM (kube-reserved) from cgroup. It decreases a
  chance of overcommitment
- Add a possibility to modify Kubelet node-status-update-frequency
- Add a posibility to configure node-monitor-grace-period,
  node-monitor-period, pod-eviction-timeout for Kubernetes controller
  manager
- Add Kubernetes Relaibility Documentation with recomendations for
  various scenarios.

Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>
2017-02-09 23:54:08 +01:00

48 lines
2.2 KiB
Markdown

Large deployments of K8s
========================
For a large scaled deployments, consider the following configuration changes:
* Tune [ansible settings]
(http://docs.ansible.com/ansible/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 master node) then retrying failed
push or download operations.
* Tune parameters for DNS related applications (dnsmasq daemon set, kubedns
replication controller). 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_controller_pod_eviction_timeout`` for better Kubernetes reliability.
Check out [Kubernetes Reliability](kubernetes-reliability.md)
* Add calico-rr nodes if you are deploying with Calico or Canal. Nodes recover
from host/network interruption much quicker with calico-rr. Note that
calico-rr role must be on a host without kube-master or kube-node role (but
etcd role is okay).
* Check out the
[Inventory](getting-started.md#building-your-own-inventory)
section of the Getting started guide for tips on creating a large scale
Ansible inventory.
For example, when deploying 200 nodes, you may want to run ansible with
``--forks=50``, ``--timeout=600`` and define the ``retry_stagger: 60``.