Integrating an instance group with Network Load Balancer or Application Load Balancer

Using Yandex Network Load Balancer and Yandex Application Load Balancer, you can evenly distribute the workload across Yandex Compute Cloud VM instances. An instance group can be integrated with these services: Compute Cloud will automatically create a Network Load Balancer or Application Load Balancer target group from this instance group and perform monitoring so that unhealthy instances are not added to the group.

How integration worksHow integration works

Creating a target groupCreating a target group

In Yandex Cloud load balancing services, a target group is a set of resources where your network applications are running. The load balancer the target group is linked to distributes incoming requests across its resources. To learn more about target groups, see the Network Load Balancer and Application Load Balancer documentation.

Target groups usually include Compute Cloud VM instances. This allows you to set up an instance group so that a Network Load Balancer or Application Load Balancer target group could be created automatically from it. The target group created this way will be associated with the instance group:

• When an instance is added to the instance group or restarted after being stopped, it is added to the target group.
• When an instance is stopped or removed from the instance group, it is removed from the target group.

To make sure the target group starts receiving traffic, link it to a load balancer. Compute Cloud does not do that automatically.

• The Network Load Balancer target group should be linked to the load balancer directly.
• The Application Load Balancer target group should be linked to a backend group and the backend group, to the load balancer, either directly or via an HTTP router, depending on the load balancing type. For more information, see our guides for managing Application Load Balancer resources.

Health checks from load balancersHealth checks from load balancers

Once a target group is linked to a load balancer, it sends health checks to the group instances to find out which of them are healthy and which are not when distributing traffic. To learn more about health checks, see the Network Load Balancer and Application Load Balancer documentation.

When you add an instance to the group or restart a stopped one, this instance is added to the target group, gets the OPENING_TRAFFIC status in the instance group, and starts receiving health checks from the load balancer. If the instance passes the required number of health checks (the healthy threshold you set when configuring health checks), the load balancer considers it healthy. The instance starts receiving traffic from the load balancer and switches to the RUNNING_ACTUAL status.

By default, an instance may have the OPENING_TRAFFIC status indefinitely until it gets healthy. You can limit this time in the integration settings (the max_opening_traffic_duration field). Compute Cloud will then automatically recover the instance that has received no traffic for too long since it was added to the group or started. For more information about VM recovery, see Autohealing features.

You can disable load balancer health checks using the ignore_health_checks parameter. In this case, the checks will not affect the instance group in any way. Negative check results will not prompt the instances to autoheal, and the group will receive no traffic from load balancers.

SettingsSettings

You can integrate an instance group with Network Load Balancer or Application Load Balancer in the management console or describe the integration in the group's YAML specification to provide the specification through the Yandex Cloud CLI or API. You can specify the settings when creating or updating a group.

An instance group can only be integrated with one of the services: either Network Load Balancer or Application Load Balancer. You cannot set up integration of an instance group with both services at the same time.

Below, you can find the descriptions of the fields with the settings from the YAML specification and their respective fields in the management console.

Settings for integration with Network Load BalancerSettings for integration with Network Load Balancer

load_balancer_spec:
  target_group_spec:
    name: "ig-tg"
    description: "Instance group as target group"
    labels:
      foo: "baz"
      bar: "baz"
  max_opening_traffic_duration: 30s
  ignore_health_checks: false

The fields and options in the management console are located under Integration with Network Load Balancer on the instance group creation and editing pages.

Settings for integration with Application Load BalancerSettings for integration with Application Load Balancer

application_load_balancer_spec:
  target_group_spec:
    name: "ig-tg"
    description: "Instance group as target group"
    labels:
      foo: "baz"
      bar: "baz"
  max_opening_traffic_duration: 30s
  ignore_health_checks: false

The fields and options in the management console are located under Integration with Application Load Balancer on the instance group creation and editing pages.