Performing one-click OS image upgrades in MIGs (original) (raw)

By using a combination of customimage familiesandrolling updates, you can enable one-click OS image upgrades on yourmanaged instance group(MIG).

Using the one-click OS image upgrade provides a number of benefits, including:

Before you begin

How does one-click OS image upgrade work?

When you invoke an update, the MIG replaces the boot disks for all VMs in the group with the latest available OS image version from your custom image family. The MIG preserves metadata and startup scripts that you set up in the instance template for each VM in the group. Non-boot disks are recreated based on their specification in the instance template. For information about preserving data, seeConfiguring stateful disks in MIGs.

To limit application disruption, you can perform updates in batches, keeping a specific percent of VMs running during the update. To increase reliability, you can configure an application-based health check for your MIG: the group waits for a healthy response from an application on updated VMs before proceeding with further updates to other VMs.

Before you begin

To update all the VMs in a MIG to the latest image from a custom image family, complete the following steps:

  1. Start a rolling replace with the following command.
    gcloud compute instance-groups managed rolling-action replace instance-group-name \
    [--max-surge=max-surge ] [--max-unavailable=max-unavailable]
    Replace the following:
    • instance-group-name: the name of the MIG to operate on.
    • max-surge: the maximum additional number of VMs that can be temporarily created during the update process. This can be a fixed number (for example, 5) or a percentage of the size of the MIG (for example, 10%).
    • max-unavailable: the maximum number of VMs that can be unavailable during the update process. This can be a fixed number (5) or a percentage of the size of the MIG (10%).
      You can combine health checks by using the --max-unavailable and--max-surge optionsto stop further updates if they cause VMs to become unavailable.
  2. Monitor the updateby using thewait-untilsubcommand to check that the MIG's status.versionTarget.isReached field is set to true.
    gcloud compute instance-groups managed wait-until instance-group-name --version-target-reached
    Replace the following:
    • instance-group-name: the name of the MIG to operate on.
      The command returns when the group is updated.
      You can alsolist instancesto see each instance's status.
      gcloud compute instance-groups managed list-instances instance-group-name
      The command returns a list of instances and their details, includingstatus,health state, andcurrent actionsfor each VM. When all VMs are RUNNING and have no current action, then the MIG is up-to-date andstable.
  3. In case you need to roll back to a previous OS image, you must create an instance template and specify the image you want to use. Thenstart a rolling updateto update all managed instances to use that template. For more information, seeRolling back an update.

Example

This example covers the following tasks:

  1. Create an instance template for easy OS image updates:
  2. Create a MIG based on the template.
  3. Set up a health check to limit disruption by an image update.
  4. Add a new image to an image family.
  5. Invoke an OS update with a single command.
  6. Monitor the update.

Use the following steps to enable and perform one-click OS upgrades on a MIG:

  1. Create an instance template that specifies a custom image family. The image family should contain tested and trusted images. Each VM that the MIG creates from the template uses the latest available image from this family.
    gcloud compute instance-templates create example-template \
    --machine-type n1-standard-4 \
    --image-family my-image-family \
    --image-project my-project \
    --tags=http-server
  2. Create a MIG based on the instance template. This example starts the MIG with three instances based on example-template. Because the instance template specifies an image family, the MIG creates each VM with the latest image from the family.
    gcloud compute instance-groups managed create example-group \
    --base-instance-name example \
    --size 3 \
    --zone us-east1-b \
    --template example-template
  3. Optional: Configure and enable an application-based health check. If your app doesn't respond after an image update, you can use the health check status combined with themaxUnavailablesetting to stop the MIG from further rollouts.
    1. Create a health check that looks for an HTTP 200 response on the request path /health. The GitHub app that is on each instance serves that path.
      gcloud compute health-checks create http example-autohealer-check \
      --check-interval 10 \
      --timeout 5 \
      --healthy-threshold 2 \
      --unhealthy-threshold 3 \
      --request-path "/health"
    2. Create a firewall rule to allow the health checker probes to access the instances. The health checker probes come from addresses in the ranges:130.211.0.0/22 and 35.191.0.0/16
      gcloud compute firewall-rules create default-allow-http-health-check \
      --network default \
      --allow tcp:80 \
      --source-ranges 130.211.0.0/22,35.191.0.0/16
    3. Add the health check to your MIG.
      gcloud compute instance-groups managed update example-group \
      --zone us-east1-b --health-check example-autohealer-check
  4. When an update is available, tested, and determined to be compatible with your app, create a new image, and use the --family flag to include that image in the custom image family.
    gcloud compute images my-image-v2 \
    --source-disk boot-disk-1 \
    --source-disk-zone us-central1-f \
    --family my-image-family
    In this example, the latest image in my-image-family is now my-image-v2, which is based on the source disk boot-disk-1.
  5. Invoke a rolling replace to replace all VMs in the MIG. The MIG replaces each VM based on the group's instance template. The instance template specifies my-image-family, so each VM gets the latest image in the family (my-image-v2).
    You canconfigurethe level of disruption that the update causes. In this example, the MIG creates one additional VM above the group's target size, and it does not remove any existing VMs until that one VM is up and running.
    gcloud compute instance-groups managed rolling-action replace example-group \
    --max-surge 1 --max-unavailable 0
  6. If you want to monitor the status of the updates, use thewait-until commandwith the --version-target-reached flag. The command returns when the group is updated.
    gcloud compute instance-groups managed wait-until --version-target-reached example-group \
    --zone us-east1-
    Waiting for group to reach version target
    ...
    Version target is reached
    You can also use thelist-instances commandto see thestatus,health state,current actions, instance template, and version for each VM.
    gcloud compute instance-groups managed list-instances example-group \
    --zone us-east1-b
    NAME ZONE STATUS HEALTH_STATE ACTION INSTANCE_TEMPLATE VERSION_NAME LAST_ERROR
    test-211p us-east1-b RUNNING HEALTHY NONE example-template 0/2020-01-30 13:34:28.843377+00:00
    test-t5qb us-east1-b RUNNING UNKNOWN VERIFYING example-template 0/2020-01-30 13:34:28.843377+00:00
    test-x331 us-east1-b RUNNING HEALTHY NONE example-template 0/2020-01-20 20:39:51.819399+00:00
  7. If you need torollbackto a previous image, use the following steps:
    1. Create a new instance templatethat specifies the image that you want.
    2. Start a rolling updateto apply the instance template.

What's next