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How to Expand a Load Balanced Application to an Additional Availability Zone

From Amazon Elastic Load Balancing: 2009-05-15

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How to Expand a Load Balanced Application to an Additional Availability Zone

In this example, you expand your EC2 application to run in an additional Availability Zone (us-east-1b). To do so, you first register the instances in the Availability Zone us-east-1b with the LoadBalancer. You wait for the instances to show up in the OutOfService state for the LoadBalancer. Finally you enable Availability Zone us-east-1b for your LoadBalancer.

[Note] Note

It is important to register instances in the new Availability Zone with your LoadBalancer before adding the Availability Zone. When you call EnableAvailabilityZonesForLoadBalancer, the LoadBalancer begins to route traffic equally amongst all the enabled Availability Zones. If the instances have not been registered, requests going to the new Availability Zone will fail.

Preconditions:

  • You have set up an HTTP LoadBalancer in Availability Zone us-east-1a as in Setting up a Load Balance to Use HTTP.

  • In Availability Zone us-east-1b, you have launched the instances you intend to register with your LoadBalancer.

API Example

To expand a load balanced application to an additional Availability Zone

  1. Call RegisterInstancesWithLoadBalancer with the following parameters:

    • LoadBalancerName = MyLoadBalancer

    • Instances = [i-3a8cf324, i-2603ca33]

  2. Call DescribeInstanceHealth with the following parameters.

    • LoadBalancerName = MyLoadBalancer

    • Instances = i-3a8cf324, i-2603ca33

  3. When the instances from the previous step are in the OutOfService state, you can proceed to the next step. Call EnableAvailabilityZonesForLoadBalancer.

    • LoadBalancerName = MyLoadBalancer

    • Availability Zones = us-east-1b

The operation returns the updated list of Availability Zones enabled for your LoadBalancer.

Command Line Tools Example

To expand a load balanced application to an additional Availability Zone

  1. Use the elb-register-instances-with-lb command as in the following example.

    PROMPT> elb-register-instances-with-lb  MyLoadBalancer  --headers --instances i-3a8cf324, i-2603ca33

    Elastic Load Balancing returns the following:

    INSTANCE  INSTANCE-ID
INSTANCE  i-3a8cf324
INSTANCE  i-2603ca33
INSTANCE  i-4f8cf126
INSTANCE  i-0bb7ca62

  2. Use the elb-describe-instance-health command as in the following example.

    PROMPT> elb-describe-instance-health  MyLoadBalancer  --headers --instances i-3a8cf324,i-2603ca33

    Elastic Load Balancing returns the following:

    INSTANCE  INSTANCE-ID STATE
INSTANCE  i-3a8cf324 OutOfService
INSTANCE  i-2603ca33 OutOfService

  3. Use the elb-enable-zones-for-lb command as in the following example.

    PROMPT>elb-enable-zones-for-lb  MyLoadBalancer  --headers --availability-zones us-east-1b

    Elastic Load Balancing returns the following:

    AVAILABILITY_ZONES  AVAILABILITY-ZONES
AVAILABILITY_ZONES  us-east-1a, us-east-1b

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