Sameness groups configuration entry reference

This page provides reference information for sameness group configuration entries. Sameness groups associate identical admin partitions to facilitate traffic between identical services. When partitions are part of the same Consul datacenter, you can create a sameness group by listing them in the Members[].Partition field. When partitions are located on remote clusters, you must establish cluster peering connections between remote partitions in order to add them to a sameness group in the Members[].Peer field.

To learn more about creating a sameness group, refer to Create sameness groups or Create sameness groups on Kubernetes.

Configuration model

The following list outlines field hierarchy, language-specific data types, and requirements in the sameness group configuration entry. Click on a property name to view additional details, including default values.

Kind: string | required | must be set to sameness-group
Name: string | required
Partition: string | default
DefaultForFailover: boolean | false
IncludeLocal: boolean | false
Members: list of maps | required
- Partition: string
- Peer: string

Complete configuration

When every field is defined, a sameness group configuration entry has the following form:

Kind               = "sameness-group"             # required
Name               = "<group-name>"               # required
Partition          = "<partition-configuration-applies-to>"
DefaultForFailover = false
IncludeLocal       = true
Members = [                                       # required
  { Partition = "<partition-with-services-in-group>" },
  { Peer = "<cluster-peer-with-services-in-group>" }
]

{
    "Kind": "sameness-group",                           // required
    "Name": "<group-name>",                             // required
    "Partition": "<partition-configuration-applies-to>",
    "DefaultForFailover": false,
    "IncludeLocal": true,    
    "Members": [                                        // required
        {
            "Partition": "<partition-with-services-in-group>"
        },
        {
            "Peer": "<cluster-peer-with-services-in-group>"
        }
    ]
}

apiVersion: consul.hashicorp.com/v1alpha1         # required
kind: SamenessGroup                               # required
metadata:
  name: <groupName>
spec:
  defaultForFailover: false
  includeLocal: true
  members:                                        # required
    - partition: <partitionWithServicesInGroup>
    - peer: <clusterPeerWithServicesInGroup>

Specifications

This section provides details about the fields you can configure in the sameness group configuration entry.

`Kind`

Specifies the type of configuration entry to implement. Must be set to sameness-group.

Values

Default: None
This field is required.
Data type: String value that must be set to sameness-group.

`Name`

Specifies a name for the configuration entry that is used to identify the sameness group. To ensure consistency, use descriptive names and make sure that the same name is used when creating configuration entries to add each member to the sameness group.

Values

Default: None
This field is required.
Data type: String

`Partition`

Specifies the local admin partition that the sameness group applies to. Refer to admin partitions for more information.

Values

Default: default
Data type: String

`DefaultForFailover`

Determines whether the sameness group should be used to establish connections to services with the same name during failover scenarios.

When this field is set to true, upstream requests automatically fail over to services in the sameness group according to the order of the members in the Members list. It impacts all services on the partition.

When this field is set to false, you can use a sameness group for failover by configuring the Failover block of a service resolver configuration entry.

When you query Consul DNS using sameness groups, DefaultForFailover must be set to true. Otherwise, Consul DNS returns an error.

Values

Default: false
Data type: Boolean

`IncludeLocal`

Determines whether the local partition should be considered the first member of the sameness group. When this field is set to true, DNS queries, upstream requests, and failover traffic returns a health instance from the local partition unless one does not exist.

If you enable this parameter, you do not need to list the local partition as the first member in the group.

Values

Default: false
Data type: Boolean

`Members`

Specifies the partitions and cluster peers that are members of the sameness group from the perspective of the local partition.

The local partition should be the first member listed unless IncludeLocal=true. The order of the members determines their precedence during failover scenarios. If a member is listed but Consul cannot connect to it, failover proceeds with the next healthy member in the list. For an example demonstrating how to configure this parameter, refer to Failover between sameness groups.

Each partition can belong to a single sameness group. You cannot associate a partition or cluster peer with multiple sameness groups.

Values

Default: None
This field is required.
Data type: List that can contain maps of the following parameters:
- Partition
- Peer

`Members[].Partition`

Specifies a partition in the local datacenter that is a member of the sameness group. Local partitions do not require cluster peering connections before they are added to a sameness group.

Values

Default: None
Data type: String

`Members[].Peer`

Specifies the name of a cluster peer that is a member of the sameness group.

Cluster peering connections must be established before adding a remote partition to the list of members. Refer to establish cluster peering connections for more information.

Values

Default: None
Data type: String

`apiVersion`

Specifies the version of the Consul API for integrating with Kubernetes. The value must be consul.hashicorp.com/v1alpha1.

Values

Default: None
This field is required.
String value that must be set to consul.hashicorp.com/v1alpha1.

`kind`

Specifies the type of configuration entry to implement. Must be set to SamenessGroup.

Values

Default: None
This field is required.
Data type: String value that must be set to SamenessGroup.

`metadata`

Map that contains an arbitrary name for the configuration entry and the namespace it applies to.

Values

Default: None
Data type: Map

`metadata.name`

Values

Default: None
This field is required.
Data type: String

`spec`

Map that contains the details about the SamenessGroup configuration entry. The apiVersion, kind, and metadata fields are siblings of the spec field. All other configurations are children.

Values

Default: None
This field is required.
Data type: Map

`spec.defaultForFailover`

Determines whether the sameness group should be used to establish connections to services with the same name during failover scenarios. When this field is set to true, upstream requests automatically failover to services in the sameness group according to the order of the members in the spec.members list. This setting affects all services on the partition.

When this field is set to false, you can use a sameness group for failover by configuring the spec.failover block of a service resolver CRD.

Values

Default: false
Data type: Boolean

`spec.includeLocal`

Determines whether the local partition should be considered the first member of the sameness group. When this field is set to true, DNS queries, upstream requests, and failover traffic target return a healthy instance from the local partition unless a healthy instance does not exist.

If you enable this parameter, you do not need to list the local partition as the first member in the group.

Values

Default: false
Data type: Boolean

`spec.members`

Specifies the local partitions and cluster peers that are members of the sameness group from the perspective of the local partition.

The local partition should be the first member listed unless spec.includeLocal: true. The order of the members determines their precedence during failover scenarios. If a member is listed but Consul cannot connect to it, failover proceeds with the next healthy member in the list. For an example demonstrating how to configure this parameter, refer to Failover between sameness groups.

Each partition can belong to a single sameness group. You cannot associate a partition or cluster peer with multiple sameness groups.

Values

Default: None
This field is required.
Data type: List that can contain maps of the following parameters:
- partition
- peer

`spec.members[].partition`

Specifies a partition in the local datacenter that is a member of the sameness group. Local partitions do not require cluster peering connections before they are added to a sameness group.

Values

Default: None
Data type: String

`spec.members[].peer`

Specifies the name of a cluster peer that is a member of the sameness group.

Cluster peering connections must be established before adding a peer to the list of members. Refer to establish cluster peering connections for more information.

Values

Default: None
Data type: String

Examples

The following examples demonstrate common sameness group configuration patterns for specific use cases.

Failover between members of a sameness group

In the following example, the configuration entry defines a sameness group named products-api that applies to the store-east partition in the local datacenter. The sameness group is configured so that when a service instance in store-east fails, Consul attempts to establish a failover connection in the following order:

Services with the same name in the store-east partition
Services with the same name in the inventory-east partition in the same datacenter
Services with the same name in the store-west partition of datacenter dc2, which has an established cluster peering connection.
Services with the same name in the inventory-west partition of dc2, which has an established cluster peering connection.

Kind                     = "sameness-group"  
Name                     = "products-api"
Partition                = "store-east"
Members = [
    { Partition = "store-east" },
    { Partition = "inventory-east" },
    { Peer      = "dc2-store-west" },
    { Peer      = "dc2-inventory-west" }
]

{
    "Kind": "sameness-group", 
    "Name": "products-api", 
    "Partition": "store-east",
    "Members": [
        {
            "Partition": "store-east"
        },
        {
            "Partition": "inventory-east"
        },
        {
            "Peer": "dc2-store-west"
        },
        {
            "Peer": "dc2-inventory-west"
        }
    ]
}

apiVersion: consul.hashicorp.com/v1alpha1
kind: SamenessGroup 
metadata:
  name: products-api
spec:
  members:                                   
    - partition: store-east
    - partition: inventory-east
    - peer: dc2-store-west
    - peer: dc2-inventory-west