c12s-kubespray/docs/large-deployments.md
Bogdan Dobrelya 2d18e19263 Tune dnsmasq/kubedns limits, replicas, logging
* Add dns_replicas, dns_memory/cpu_limit/requests vars for
dns related apps.
* When kube_log_level=4, log dnsmasq queries as well.
* Add log level control for skydns (part of kubedns app).
* Add limits/requests vars for dnsmasq (part of kubedns app) and
  dnsmasq daemon set.
* Drop string defaults for kube_log_level as it is int and
  is defined in the global vars as well.
* Add docs

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
2016-11-25 12:49:17 +01:00

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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`` to download container images only once
then push to cluster nodes in batches. The default delegate node
for pushing images is the first kube-master. Note, if you have passwordless sudo
and docker enabled on the separate admin node, you may want to define the
``download_localhost: true``, which makes that node a delegate for pushing images
while running the deployment with ansible. This maybe the case if cluster nodes
cannot access each over via ssh or you want to use local docker images as a cache
for multiple clusters.
* 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.
For example, when deploying 200 nodes, you may want to run ansible with
``--forks=50``, ``--timeout=600`` and define the ``retry_stagger: 60``.