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Cluster Retraction

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Objective

This guide provides instructions on how to configure fallback in case of endpoints behind a cluster that are not healthy. Cluster groups a set of endpoints together into a resource pool that is used in the load balancer configuration. To learn more about endpoints and load balancers, see Load Balancing and Service Mesh.

When a route points to multiple clusters as part of a weighted cluster configuration, and any of the clusters have no healthy endpoints, then traffic to the route is distributed only among the remaining clusters that have one or more healthy endpoints. This is referred to as cluster retracting. An endpoint is deemed unhealthy in case a health-check fails or endpoint discovery fails.

Using the instructions provided in this guide, you can enable or disable cluster retraction for an HTTP or TCP load balancer.

Note: Cluster retraction is enabled by default for HTTP and TCP load balancers. This means that weighted cluster configuration of route and panic-threshold configuration for a cluster may not work when any cluster gets retracted because of no healthy endpoints.

Prerequisites

The following prerequisites apply:

Configuration

Cluster retraction is enabled by default for HTTP and TCP load balancers. You can disable it while creating a new load balancer, or you can enable or disable it for an existing load balancer. This example shows how to update an existing load balancer to enable or disable cluster retraction for an HTTP load balancer.

Perform the following steps to enable or disable cluster retraction:

Step 1: Navigate to the load balancer configuration.

  • Log into F5® Distributed Cloud Console (Console).

  • Click Load Balancers.

Figure: Console Homepage
Figure: Console Homepage

  • Change to your application namespace.

  • Click Manage > Load Balancers > HTTP Load Balancers.

Figure: HTTP Load Balancers
Figure: HTTP Load Balancers

  • Click ... > Manage Configuration > Edit Configuration for your HTTP load balancer from the displayed list.

Figure: Edit HTTP Load Balancers
Figure: Edit HTTP Load Balancers

Step 2: Start editing the route configuration.

  • In the Routes Configuration section, enable the Show Advanced Fields option.

  • Click Configure to open the route configuration page.

  • Click Add Item.

Step 3: Configure cluster retraction.

  • Under the Advanced Fields section, click Configure for the route entries for which you want to enable the cluster retraction.

  • In the Select Cluster retract option section, enable the Show Advanced Fields option.

  • From the Select Cluster retract option menu, select one of the following options:

    • Select Retract cluster with no healthy endpoints to enable cluster retraction.

    • Select Disable cluster retraction to disable cluster retraction.

Cluster Retraction Settings
Figure: Cluster Retraction Settings

  • Click Apply to apply the cluster retraction setting to the route configuration.

  • Click Add Item in the route configuration page to apply the changes to the load balancer configuration.

  • Click Apply.

Step 4: Complete applying cluster retraction to load balancer.

Click Save and Exit.

Note: Any subsequent endpoint failures result in performing cluster retraction.

Concepts

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