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This guide explains why and how to manage multiple Kubernetes clusters using
Federation makes it easy to manage multiple clusters. It does so by providing 2
major building blocks:
- Sync resources across clusters: Federation provides the ability to keep
resources in multiple clusters in sync. This can be used, for example, to
ensure that the same deployment exists in multiple clusters.
- Cross cluster discovery: It provides the ability to auto-configure DNS
servers and load balancers with backends from all clusters. This can be used,
for example, to ensure that a global VIP or DNS record can be used to access
backends from multiple clusters.
Some other use cases that federation enables are:
- High Availability: By spreading load across clusters and auto configuring DNS
servers and load balancers, federation minimises the impact of cluster
- Avoiding provider lock-in: By making it easier to migrate applications across
clusters, federation prevents cluster provider lock-in.
Federation is not helpful unless you have multiple clusters. Some of the reasons
why you might want multiple clusters are:
- Low latency: Having clusters in multiple regions minimises latency by serving
users from the cluster that is closest to them.
- Fault isolation: It might be better to have multiple small clusters rather
than a single large cluster for fault isolation (for example: multiple
clusters in different availability zones of a cloud provider).
Multi cluster guide has more details on this.
- Scalability: There are scalability limits to a single kubernetes cluster (this
should not be the case for most users. For more details:
Kubernetes Scaling and Performance Goals).
- Hybrid cloud: You can have multiple clusters on different cloud providers or
on-premises data centers.
While there are a lot of attractive use cases for federation, there are also
- Increased network bandwidth and cost: The federation control plane watches all
clusters to ensure that the current state is as expected. This can lead to
significant network cost if the clusters are running in different regions on
a cloud provider or on different cloud providers.
- Reduced cross cluster isolation: A bug in the federation control plane can
impact all clusters. This is mitigated by keeping the logic in federation
control plane to a minimum. It mostly delegates to the control plane in
kubernetes clusters whenever it can. The design and implementation also errs
on the side of safety and avoiding multicluster outage.
- Maturity: The federation project is relatively new and is not very mature.
Not all resources are available and many are still alpha. Issue
known issues with the system that the team is busy solving.
To be able to federate multiple clusters, we first need to setup a federation
Follow the setup guide to setup the
federation control plane.
Hybrid cloud capabilities
Federations of Kubernetes Clusters can include clusters running in
different cloud providers (e.g. Google Cloud, AWS), and on-premises
(e.g. on OpenStack). Simply create all of the clusters that you
require, in the appropriate cloud providers and/or locations, and
register each cluster’s API endpoint and credentials with your
Federation API Server (See the
federation admin guide for details).
Thereafter, your API resources can span different clusters
and cloud providers.
Once we have the control plane setup, we can start creating federation API
The following guides explain some of the resources in detail:
API reference docs lists all the
resources supported by federation apiserver.
Kubernetes version 1.6 includes support for cascading deletion of federated
resources. With cascading deletion, when you delete a resource from the
federation control plane, the corresponding resources in all underlying clusters
are also deleted.
Cascading deletion is not enabled by default when using the REST API. To enable
it, set the option
DeleteOptions.orphanDependents=false when you delete a
resource from the federation control plane using REST API. Using
will enable cascading deletion by default. You can disable it by running
Note: Kubernetes version 1.5 included cascading deletion support for a subset of
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