Defining Installation Order for Native Helm Charts

This topic describes how to use the weight property to define the installation order for charts deployed with the native Helm method. For more information about using native Helm charts with Replicated, see About Deploying Helm Charts.

About Native Helm Chart Installation Weight

For Helm charts deployed with native Helm, you can add a weight property to the HelmChart custom resource manifest file to define the order in which Helm installs the charts.

This is useful if you have multiple HelmChart custom resources in your application, and it is important that the resources referenced in one or more Helm charts are deployed before one or more other Helm charts.

Assigning a weight also helps you avoid relying on Helm dependencies and subcharts to define a chart installation order in Replicated KOTS. This is particularly useful when you include hooks in your native Helm charts, as Helm waits for certain hooks to complete before continuing. For more information about how KOTS handles dependencies and hooks for Helm charts, see Subcharts and Dependencies and Hooks below.

KOTS directs Helm to install the native Helm charts in your application based on the value of weight in ascending order, deploying the chart with the lowest weight first. For example, a chart with a weight of -1 deploys before a chart with a weight of 0.

The value for the weight property can be any negative or positive integer or 0. By default, when you do not provide a weight for a native Helm chart, the weight is 0.

Assign Installation Weight to Native Helm Charts

You can add a weight property to any native Helm charts in your application to define the order in which they are installed.

To add a weight to native Helm charts:

1. Open the manifest file for the HelmChart custom resource you want to assign an installation order.

2. Add the following line to the HelmChart custom resource manifest file at the same level as useHelmInstall: true:

   weight: INSTALL-WEIGHT

   Where INSTALL-WEIGHT is any negative or positive integer or 0.

   Example::

   apiVersion: kots.io/v1beta1
   kind: HelmChart
   metadata:
     name: samplechart
   spec:
     chart:
       name: samplechart
       chartVersion: 3.1.7
   
     exclude: "repl{{ ConfigOptionEquals `include_chart` `include_chart_no`}}"
   
     helmVersion: v3
   
     useHelmInstall: true
     weight: 1
   
     values:
       ...
   
     namespace: samplechart-namespace

3. Save your changes.

Subcharts and Dependencies

When you add a weight property to HelmChart custom resources in your application, KOTS instructs Helm to install any dependencies, including subcharts, along with the parent chart.

For example, if you have two native Helm charts in your application, one with a weight of -1 and one with a weight of 0, then Helm installs the chart with a weight of -1 first, including any subcharts and dependencies listed in the dependencies field for that chart.

If you do not add a weight to native Helm charts in your application, you can still use dependencies and subcharts to define installation order constraints during application deployment.

For more information about using Helm dependencies, see Chart Dependencies in the Helm documentation.

Hooks

Helm hooks enable more control over when Helm installs the resources in your Helm charts. This is useful if you want to bundle actions as part of a release. For example, you can build in a database backup as part of the upgrade process while ensuring that the backup occurs prior to upgrading the rest of the resources.

KOTS supports using some Helm hooks with native Helm charts. If you use hooks in your native Helm charts, you can use the weight property to further manage the installation order of resources. For example, if you include a pre-install hook in Helm chart A that requires a resource from Helm chart B, you can add a lower weight to chart B to ensure that Replicated KOTS directs Helm to install chart B before chart A.

The following hooks are supported:

• pre-install: Executes after resources are rendered but before any resources are installed.
• post-install: Executes after resources are installed.
• pre-upgrade: Executes after resources are rendered but before any resources are upgraded.
• post-upgrade: Executes after resources are upgraded.
• pre-delete: Executes before any resources are deleted.
• post-delete: Executes after resources are deleted.

The following hooks are not supported and are ignored if they are present:

• test
• pre-rollback
• post-rollback

For more information about Helm hooks and weights, see the Chart Hooks in the Helm documentation.