Use Planned Maintenance to schedule and control upgrades for your Azure Kubernetes Service (AKS) cluster

Article
08/18/2023

Your AKS cluster has regular maintenance performed on it automatically. There are two types of regular maintenance - AKS initiated and those that you initiate. Planned Maintenance feature allows you to run both types of maintenance in a cadence of your choice thereby minimizing any workload impact.

AKS intiated maintenance refers to the AKS releases. These releases are weekly rounds of fixes and feature and component updates that affect your clusters. The type of maintenance that you initiate regularly are cluster auto-upgrades and Node OS automatic security updates.

There are currently three available configuration types: default, aksManagedAutoUpgradeSchedule, aksManagedNodeOSUpgradeSchedule:

default corresponds to a basic configuration that is used to control AKS releases, these releases can take up to two weeks to roll out to all regions from the initial time of shipping due to Azure Safe Deployment Practices (SDP). Choose default to schedule these updates in such a way that it's least disruptive for you. You can monitor the status of an ongoing AKS release by region from the weekly releases tracker.
aksManagedAutoUpgradeSchedule controls when cluster upgrades scheduled by your designated auto-upgrade channel are performed. More finely controlled cadence and recurrence settings are possible than in a default configuration. For more information on cluster auto-upgrade, see Automatically upgrade an Azure Kubernetes Service (AKS) cluster.
aksManagedNodeOSUpgradeSchedule controls when the node operating system security patching scheduled by your node OS auto-upgrade channel are performed. More finely controlled cadence and recurrence settings are possible than in a `default configuration. For more information on node OS auto-upgrade channel, see Automatically patch and update AKS cluster node images

We recommend using aksManagedAutoUpgradeSchedule for all cluster upgrade scenarios and aksManagedNodeOSUpgradeSchedule for all node OS security patching scenarios, while default is meant exclusively for the AKS weekly releases. You can port default configurations to the aksManagedAutoUpgradeSchedule or aksManagedNodeOSUpgradeSchedule configurations via the az aks maintenanceconfiguration update command.

Before you begin

This article assumes that you have an existing AKS cluster. If you need an AKS cluster, see the AKS quickstart using the Azure CLI, using Azure PowerShell, or using the Azure portal.

Be sure to upgrade Azure CLI to the latest version using az upgrade.

Creating a maintenance window

To create a maintenance window, you can use the az aks maintenanceconfiguration add command using the --name value default, aksManagedAutoUpgradeSchedule, or aksManagedNodeOSUpgradeSchedule. The name value should reflect the desired configuration type. Using any other name causes your maintenance window not to run.

Note

When using auto-upgrade, to ensure proper functionality, use a maintenance window with a duration of four hours or more.

Planned Maintenance windows are specified in Coordinated Universal Time (UTC).

A default maintenance window has the following properties:

Name	Description	Default value
`timeInWeek`	In a `default` configuration, this property contains the `day` and `hourSlots` values defining a maintenance window	N/A
`timeInWeek.day`	The day of the week to perform maintenance in a `default` configuration	N/A
`timeInWeek.hourSlots`	A list of hour-long time slots to perform maintenance on a given day in a `default` configuration	N/A
`notAllowedTime`	Specifies a range of dates that maintenance can't run, determined by `start` and `end` child properties. Only applicable when creating the maintenance window using a config file	N/A

An aksManagedAutoUpgradeSchedule or aksManagedNodeOSUpgradeSchedule maintenance window has the following properties:

Name	Description	Default value
`utcOffset`	Used to determine the timezone for cluster maintenance	`+00:00`
`startDate`	The date on which the maintenance window begins to take effect	The current date at creation time
`startTime`	The time for maintenance to begin, based on the timezone determined by `utcOffset`	N/A
`schedule`	Used to determine frequency. Three types are available: `Weekly`, `AbsoluteMonthly`, and `RelativeMonthly`	N/A
`intervalDays`	The interval in days for maintenance runs. Only applicable to `aksManagedNodeOSUpgradeSchedule`	N/A
`intervalWeeks`	The interval in weeks for maintenance runs	N/A
`intervalMonths`	The interval in months for maintenance runs	N/A
`dayOfWeek`	The specified day of the week for maintenance to begin	N/A
`durationHours`	The duration of the window for maintenance to run	N/A
`notAllowedDates`	Specifies a range of dates that maintenance cannot run, determined by `start` and `end` child properties. Only applicable when creating the maintenance window using a config file	N/A

Understanding schedule types

There are currently four available schedule types: Daily, Weekly, AbsoluteMonthly, and RelativeMonthly. These schedule types are only applicable to aksManagedClusterAutoUpgradeSchedule and aksManagedNodeOSUpgradeSchedule configurations. Daily schedules are only applicable to aksManagedNodeOSUpgradeSchedule types.

Note

All of the fields shown for each respective schedule type are required.

Daily schedule

Note

Daily schedules are only applicable to aksManagedNodeOSUpgradeSchedule configuration types.

A Daily schedule may look like "every three days":

"schedule": {
    "daily": {
        "intervalDays": 2
    }
}

Weekly schedule

A Weekly schedule may look like "every two weeks on Friday":

"schedule": {
    "weekly": {
        "intervalWeeks": 2,
        "dayOfWeek": "Friday"
    }
}

AbsoluteMonthly schedule

An AbsoluteMonthly schedule may look like "every three months, on the first day of the month":

"schedule": {
    "absoluteMonthly": {
        "intervalMonths": 3,
        "dayOfMonth": 1
    }
}

RelativeMonthly schedule

A RelativeMonthly schedule may look like "every two months, on the last Monday":

"schedule": {
    "relativeMonthly": {
        "intervalMonths": 2,
        "dayOfWeek": "Monday",
        "weekIndex": "Last"
    }
}

Valid values for weekIndex are First, Second, Third, Fourth, and Last.

Things to note

When you use Planned Maintenance, the following restrictions apply:

AKS reserves the right to break these windows for unplanned, reactive maintenance operations that are urgent or critical. These maintenance operations may even run during the notAllowedTime or notAllowedDates periods defined in your configuration.
Performing maintenance operations are considered best-effort only and aren't guaranteed to occur within a specified window.

Add a maintenance window configuration with Azure CLI

The following example shows a command to add a new default configuration that schedules maintenance to run from 1:00am to 2:00am every Monday:

az aks maintenanceconfiguration add -g myResourceGroup --cluster-name myAKSCluster --name default --weekday Monday --start-hour 1

Note

When using a default configuration type, to allow maintenance anytime during a day omit the --start-time parameter.

The following example shows a command to add a new aksManagedAutoUpgradeSchedule configuration that schedules maintenance to run every third Friday between 12:00 AM and 8:00 AM in the UTC+5:30 timezone:

az aks maintenanceconfiguration add -g myResourceGroup --cluster-name myAKSCluster -n aksManagedAutoUpgradeSchedule --schedule-type Weekly --day-of-week Friday --interval-weeks 3 --duration 8 --utc-offset +05:30 --start-time 00:00

Add a maintenance window configuration with a JSON file

You can also use a JSON file create a maintenance configuration instead of using parameters. This method has the added benefit of allowing maintenance to be prevented during a range of dates, specified by notAllowedTimes for default configurations and notAllowedDates for aksManagedAutoUpgradeSchedule configurations.

Create a default.json file with the following contents:

{
  "timeInWeek": [
    {
      "day": "Tuesday",
      "hour_slots": [
        1,
        2
      ]
    },
    {
      "day": "Wednesday",
      "hour_slots": [
        1,
        6
      ]
    }
  ],
  "notAllowedTime": [
    {
      "start": "2021-05-26T03:00:00Z",
      "end": "2021-05-30T12:00:00Z"
    }
  ]
}

The above JSON file specifies maintenance windows every Tuesday at 1:00am - 3:00am and every Wednesday at 1:00am - 2:00am and at 6:00am - 7:00am in the UTC timezone. There's also an exception from 2021-05-26T03:00:00Z to 2021-05-30T12:00:00Z where maintenance isn't allowed even if it overlaps with a maintenance window.

Create an autoUpgradeWindow.json file with the following contents:

{
  "properties": {
    "maintenanceWindow": {
        "schedule": {
            "absoluteMonthly": {
                "intervalMonths": 3,
                "dayOfMonth": 1
            }
        },
        "durationHours": 4,
        "utcOffset": "-08:00",
        "startTime": "09:00",
        "notAllowedDates": [
            {
                "start": "2023-12-23",
                "end": "2024-01-05"
            }
        ]
    }
  }
}

The above JSON file specifies maintenance windows every three months on the first of the month between 9:00 AM - 1:00 PM in the UTC-08 timezone. There's also an exception from 2023-12-23 to 2024-01-05 where maintenance isn't allowed even if it overlaps with a maintenance window.

The following command adds the maintenance windows from default.json and autoUpgradeWindow.json:

az aks maintenanceconfiguration add -g myResourceGroup --cluster-name myAKSCluster --name default --config-file ./test.json

az aks maintenanceconfiguration add -g myResourceGroup --cluster-name myAKSCluster --name aksManagedAutoUpgradeSchedule --config-file ./autoUpgradeWindow.json

Update an existing maintenance window

To update an existing maintenance configuration, use the az aks maintenanceconfiguration update command.

az aks maintenanceconfiguration update -g myResourceGroup --cluster-name myAKSCluster --name default --weekday Monday  --start-hour 2

List all maintenance windows in an existing cluster

To see all current maintenance configuration windows in your AKS cluster, use the az aks maintenanceconfiguration list command.

az aks maintenanceconfiguration list -g myResourceGroup --cluster-name myAKSCluster

Show a specific maintenance configuration window in an AKS cluster

To see a specific maintenance configuration window in your AKS Cluster, use the az aks maintenanceconfiguration show command.

az aks maintenanceconfiguration show -g myResourceGroup --cluster-name myAKSCluster --name aksManagedAutoUpgradeSchedule

The following example output shows the maintenance window for aksManagedAutoUpgradeSchedule:

{
  "id": "/subscriptions/<subscription>/resourceGroups/myResourceGroup/providers/Microsoft.ContainerService/managedClusters/myAKSCluster/maintenanceConfigurations/aksManagedAutoUpgradeSchedule",
  "maintenanceWindow": {
    "durationHours": 4,
    "notAllowedDates": [
      {
        "end": "2024-01-05",
        "start": "2023-12-23"
      }
    ],
    "schedule": {
      "absoluteMonthly": {
        "dayOfMonth": 1,
        "intervalMonths": 3
      },
      "daily": null,
      "relativeMonthly": null,
      "weekly": null
    },
    "startDate": "2023-01-20",
    "startTime": "09:00",
    "utcOffset": "-08:00"
  },
  "name": "aksManagedAutoUpgradeSchedule",
  "notAllowedTime": null,
  "resourceGroup": "myResourceGroup",
  "systemData": null,
  "timeInWeek": null,
  "type": null
}

Delete a certain maintenance configuration window in an existing AKS Cluster

To delete a certain maintenance configuration window in your AKS Cluster, use the az aks maintenanceconfiguration delete command.

az aks maintenanceconfiguration delete -g myResourceGroup --cluster-name myAKSCluster --name autoUpgradeSchedule

Frequently Asked Questions

How can I check the existing maintenance configurations in my cluster?

Use the az aks maintenanceconfiguration show command.
Can reactive, unplanned maintenance happen during the notAllowedTime or notAllowedDates periods too?

Yes, AKS reserves the right to break these windows for unplanned, reactive maintenance operations that are urgent or critical.
How can you tell if a maintenance event occurred?

For releases, check your cluster's region and look up release information in weekly releases and validate if it matches your maintenance schedule or not. To view the status of your auto upgrades, look up activity logs on your cluster. You may also look up specific upgrade related events as mentioned in Upgrade an AKS cluster. AKS also emits upgrade related Event Grid events. To learn more, see AKS as an Event Grid source.
Can you use more than one maintenance configuration at the same time?

Yes, you can run all three configurations i.e default, aksManagedAutoUpgradeSchedule, aksManagedNodeOSUpgradeSchedulesimultaneously. In case the windows overlap AKS decides the running order.
I configured a maintenance window, but upgrade didn't happen - why?

AKS auto-upgrade needs a certain amount of time to take the maintenance window into consideration. We recommend at least 6 hours between the creation/update of the maintenance configuration, and when it's scheduled to start.
AKS auto-upgrade didn't upgrade all my agent pools - or one of the pools was upgraded outside of the maintenance window?

If an agent pool fails to upgrade (eg. because of Pod Disruption Budgets preventing it to upgrade) or is in a Failed state, then it might be upgraded later outside of the maintenance window. This scenario is called "catch-up upgrade" and avoids letting Agent pools with a different version than the AKS control plane.
Are there any best practices for the maintenance configurations?

We recommend setting the Node OS security updates schedule to a weekly cadence if you're using NodeImage channel since a new node image gets shipped every week and daily if you opt in for SecurityPatch channel to receive daily security updates. Set the auto-upgrade schedule to a monthly cadence to stay on top of the kubernetes N-2 support policy.

Next steps

To get started with upgrading your AKS cluster, see Upgrade an AKS cluster

Use Planned Maintenance to schedule and control upgrades for your Azure Kubernetes Service (AKS) cluster

Before you begin

Creating a maintenance window

Understanding schedule types

Daily schedule

Weekly schedule

AbsoluteMonthly schedule

RelativeMonthly schedule

Things to note

Add a maintenance window configuration with Azure CLI

Add a maintenance window configuration with a JSON file

Update an existing maintenance window

List all maintenance windows in an existing cluster

Show a specific maintenance configuration window in an AKS cluster

Delete a certain maintenance configuration window in an existing AKS Cluster

Frequently Asked Questions

Next steps

Feedback

Additional resources

Additional resources