Illumina Innovates with Rancher and Kubernetes
Rancher provides the ability to use a catalog of Helm charts that make it easy to repeatedly deploy applications.
Rancher improves on Helm catalogs and charts. All native Helm charts can work within Rancher, but Rancher adds several enhancements to improve their user experience.
This section covers the following topics:
Within Rancher, you can manage catalogs at three different scopes. Global catalogs are shared across all clusters and project. There are some use cases where you might not want to share catalogs between different clusters or even projects in the same cluster. By leveraging cluster and project scoped catalogs, you will be able to provide applications for specific teams without needing to share them with all clusters and/or projects.
Applicable as of v2.4.0
In November 2019, Helm 3 was released, and some features were deprecated or refactored. It is not fully backwards compatible with Helm 2. Therefore, catalogs in Rancher need to be separated, with each catalog only using one Helm version.
When you create a custom catalog, you will have to configure the catalog to use either Helm 2 or Helm 3. This version cannot be changed later. If the catalog is added with the wrong Helm version, it will need to be deleted and re-added.
When you launch a new app from a catalog, the app will be managed by the catalog’s Helm version. A Helm 2 catalog will use Helm 2 to manage all of the apps, and a Helm 3 catalog will use Helm 3 to manage all apps.
By default, catalogs are assumed to be deployed using Helm 2. If you run an app in Rancher prior to v2.4.0, then upgrade to Rancher v2.4.0+, the app will still be managed by Helm 2.
Charts that are specific to Helm 2 should only be added to a Helm 2 catalog, and Helm 3 specific charts should only be added to a Helm 3 catalog.
Within Rancher, there are default catalogs packaged as part of Rancher. These can be enabled or disabled by an administrator. For details, refer to the section on managing built-in global catalogs.
There are two types of catalogs in Rancher: Built-in global catalogs and custom catalogs.
Any user can create custom catalogs to add into Rancher. Custom catalogs can be added into Rancher at the global level, cluster level, or project level. For details, refer to the section on adding custom catalogs and the catalog configuration reference.
In Rancher, applications are deployed from the templates in a catalog. This section covers the following topics:
Charts now support the fields rancher_min_version and rancher_max_version in the questions.yml file to specify the versions of Rancher that the chart is compatible with. When using the UI, only app versions that are valid for the version of Rancher running will be shown. API validation is done to ensure apps that don’t meet the Rancher requirements cannot be launched. An app that is already running will not be affected on a Rancher upgrade if the newer Rancher version does not meet the app’s requirements.
Available as v2.2.0
When creating applications that span multiple Kubernetes clusters, a Global DNS entry can be created to route traffic to the endpoints in all of the different clusters. An external DNS server will need be programmed to assign a fully qualified domain name (a.k.a FQDN) to your application. Rancher will use the FQDN you provide and the IP addresses where your application is running to program the DNS. Rancher will gather endpoints from all the Kubernetes clusters running your application and program the DNS.
For more information on how to use this feature, see Global DNS.