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Home Forums AWS AWS Certified Solutions Architect Professional Question on Opsworks Self Healing

  • Question on Opsworks Self Healing

  • varun-mathur

    Member
    April 30, 2020 at 8:11 am

    Opsworks Self Healing is suggested as a HA solution for EC2s in an ASG fronted by ALB.

    Since ALB health check and ASG will automatically replace failed instances, please advise why Self Healing is suggested as well. Is that not going to conflict with the ASG behavior?

    You are working as a Solutions Architect in a leading commercial bank that is building a new online banking portal to replace their obsolete online system. Due to the volume of transactions that goes through the online portal everyday, your job is to ensure that the portal is always available 24 hours a day, 7 days a week. The bank chose to deploy the portal in AWS using EC2 instances and a MySQL RDS instance for its database.

    How can you ensure high availability of the online portal even in the event of application and database server failure?

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  • Jon-Bonso

    Administrator
    May 1, 2020 at 9:32 am

    Hi Varun,

    If a layer has auto healing enabled, AWS OpsWorks Stacks automatically replaces the layer’s failed instances:

    https://docs.aws.amazon.com/opsworks/latest/userguide/workinginstances-autohealing.html

    The “auto-scaled” word in the options actually refers to Automatic load-based scaling in OpsWorks and not the actual EC2 Auto Scaling group. Please see the reference below from the official AWS Documentation to view the difference between these two :


    Automatic load-based scaling uses load metrics that are averaged across all running instances. If the metrics remain between the specified thresholds, AWS OpsWorks Stacks does not start or stop any instances. With auto healing, on the other hand, AWS OpsWorks Stacks automatically starts a new instance with the same configuration when an instance stops responding. The instance may not be able to respond due to a network issue or some problem with the instance.

    For example, suppose that your CPU upscaling threshold is 80%, and then one instance stops responding.

    If auto healing is disabled, and the remaining running instances are able to keep average CPU utilization below 80%, AWS OpsWorks Stacks does not start a new instance. It starts a replacement instance only if the average CPU utilization across the remaining instances exceeds 80%.

    If auto healing is enabled, AWS OpsWorks Stacks starts a replacement instance irrespective of the load thresholds.

    Reference:

    https://docs.aws.amazon.com/opsworks/latest/userguide/workinginstances-autoscaling.html

    Let us know if you need further assistance. The Tutorials Dojo team is dedicated to help you pass your AWS exam on your first try!

    Regards,

    Jon Bonso @ Tutorials Dojo

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