Define re-usable update strategies using Azure Kubernetes Fleet Manager

Article
11/24/2024

Administrators can control the sequence of updates to Fleet-managed clusters by defining stages, groups and optional inter-stage pauses. These sequences can be saved as update strategies which can be managed independently of update runs or auto-upgrades, allowing strategies to be reused as required.

This article covers how to define update strategies using groups and stages.

Prerequisites

Read the conceptual overview of Fleet updates, which provides an explanation of update runs, stages, groups, and strategies referenced in this guide.
You must have a Fleet resource with one or more member clusters. If not, follow the quickstart to create a Fleet resource and join Azure Kubernetes Service (AKS) clusters as members.

Set the following environment variables:

export GROUP=<resource-group>
export FLEET=<fleet-name>
export CLUSTERID=<aks-cluster-resource-id>
export STRATEGY=<strategy-name>

If you're following the Azure CLI instructions in this article, you need Azure CLI version 2.61.0 or later installed. To install or upgrade, see Install the Azure CLI.
You also need the fleet Azure CLI extension, which you can install by running the following command:
```
az extension add --name fleet
```
Run the az extension update command to update to the latest version of the extension released:
```
az extension update --name fleet
```

Assign clusters to update groups

Before clusters can be used in update strategies they must be added to update groups which can be used in update stages. Within an update stage, updates are applied to each update group in parallel. Within an update group, member clusters update sequentially.

You can assign a member cluster to a specific update group in one of two ways:

Assign to group when adding member cluster to the fleet.
Assign an existing fleet member to an update group.

Note

A fleet member can only be a part of one update group, but an update group can have multiple fleet members assigned to it. An update group itself is not a separate resource type. Update groups are only strings representing references from the fleet members. So, if all fleet members with references to a common update group are deleted, that specific update group will cease to exist as well.

Assign to group when adding member cluster to the fleet

Azure portal
Azure CLI

In the Azure portal, navigate to your Azure Kubernetes Fleet Manager resource.
From the service menu, under Settings, select Member clusters > Add.
Select the cluster that you want to add, and then select Next: Review + add.
Enter the name of the update group that you want to assign the cluster to, and then select Add.

Assign a member cluster to an update group when adding the member cluster to the fleet using the az fleet member create command with the --update-group parameter set to the name of the update group.

az fleet member create \
    --resource-group $GROUP \
    --fleet-name $FLEET \
    --name member1 \
    --member-cluster-id $CLUSTERID \
    --update-group group-1a

Assign an existing fleet member to an update group

Azure portal
Azure CLI

In the Azure portal, navigate to your Azure Kubernetes Fleet Manager resource.
From the service menu, under Settings, select Member clusters.
Select the clusters that you want to assign to an update group, and then select Assign update group
Enter the name of the update group that you want to assign the cluster to, and then select Assign.

Assign an existing fleet member to an update group using the az fleet member update command with the --update-group flag set to the name of the update group.

az fleet member update \
 --resource-group $GROUP \
 --fleet-name $FLEET \
 --name member1 \
 --update-group group-1a

Create an update strategy

An update strategy consists of one or more stages, where a stage can contain one or more update groups.

Azure portal
Azure CLI

In the Azure portal, navigate to your Azure Kubernetes Fleet Manager resource.
From the service menu, under Settings, select Multi-cluster update > Strategies, then Create.
Enter a name for the strategy.
The first time you view the page, an update strategy explanation diagram is displayed which can help visualize how strategies function.
Select Create Stage and enter:
- Stage name - name the stage - it must be unique across all stage names in the fleet.
- (Optional) Pause after stage - select this option if you would like to define a pause before moving to the next stage.
- (Optional) Pause duration - select a pre-defined duration, or enter a custom value in seconds.
Assign one or more Update Group to the stage, and then select Create.

For this scenario, we'll create stages and groups to match the details used for the Azure portal process.

Create a JSON file to define the stages and groups for the update run. Here's an example of input from the stages file (example-stages.json) that represents the strategy shown for creation via the Azure portal:

{
    "stages": [
        {
            "name": "stage-1",
            "groups": [
                {
                    "name": "group-1"
                },
                {
                    "name": "group-2"
                }
            ],
            "afterStageWaitInSeconds": 300
        },
        {
            "name": "stage-2",
            "groups": [
                {
                    "name": "group-3"
                }
            ]
        }
    ]
}

Create a new update strategy using the az fleet updatestrategy create command with the --stages flag set to the name of your JSON file.

az fleet updatestrategy create \
 --resource-group $GROUP \
 --fleet-name $FLEET \
 --name $STRATEGY \
 --stages example-stages.json

Next steps

You can use an update strategy as part of a manual update run or an auto-upgrade profile. See:

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