Describes how traffic originating in the 'from' zone or sub-zone is distributed over a set of 'to' zones. Syntax for specifying a zone is {region}/{zone}/{sub-zone} and terminal wildcards are allowed on any segment of the specification. Examples: * - matches all localities us-west/* - all zones and sub-zones within the us-west region us-west/zone-1/* - all sub-zones within us-west/zone-1

e.g. true means that turn on locality load balancing for this DestinationRule no matter what mesh wide settings is.

Specify the traffic failover policy across regions. Since zone and sub-zone failover is supported by default this only needs to be specified for regions when the operator needs to constrain traffic failover so that the default behavior of failing over to any endpoint globally does not apply. This is useful when failing over traffic across regions would not improve service health or may need to be restricted for other reasons like regulatory controls.

failoverPriority is an ordered list of labels used to sort endpoints to do priority based load balancing. This is to support traffic failover across different groups of endpoints. Suppose there are total N labels specified:

1. Endpoints matching all N labels with the client proxy have priority P(0) i.e. the highest priority. 2. Endpoints matching the first N-1 labels with the client proxy have priority P(1) i.e. second highest priority. 3. By extension of this logic, endpoints matching only the first label with the client proxy has priority P(N-1) i.e. second lowest priority. 4. All the other endpoints have priority P(N) i.e. lowest priority. Note: For a label to be considered for match, the previous labels must match, i.e. nth label would be considered matched only if first n-1 labels match. It can be any label specified on both client and server workloads. The following labels which have special semantic meaning are also supported:

• topology.istio.io/network is used to match the network metadata of an endpoint, which can be specified by pod/namespace label topology.istio.io/network, sidecar env ISTIO_META_NETWORK or MeshNetworks. - topology.istio.io/cluster is used to match the clusterID of an endpoint, which can be specified by pod label topology.istio.io/cluster or pod env ISTIO_META_CLUSTER_ID. - topology.kubernetes.io/region is used to match the region metadata of an endpoint, which maps to Kubernetes node label topology.kubernetes.io/region or the deprecated label failure-domain.beta.kubernetes.io/region. - topology.kubernetes.io/zone is used to match the zone metadata of an endpoint, which maps to Kubernetes node label topology.kubernetes.io/zone or the deprecated label failure-domain.beta.kubernetes.io/zone. - topology.istio.io/subzone is used to match the subzone metadata of an endpoint, which maps to Istio node label topology.istio.io/subzone. The below topology config indicates the following priority levels: yaml failoverPriority: - "topology.istio.io/network" - "topology.kubernetes.io/region" - "topology.kubernetes.io/zone" - "topology.istio.io/subzone"

1. endpoints match same [network, region, zone, subzone] label with the client proxy have the highest priority. 2. endpoints have same [network, region, zone] label but different [subzone] label with the client proxy have the second highest priority. 3. endpoints have same [network, region] label but different [zone] label with the client proxy have the third highest priority. 4. endpoints have same [network] but different [region] labels with the client proxy have the fourth highest priority. 5. all the other endpoints have the same lowest priority. Optional: only one of distribute, failover or failoverPriority can be set. And it should be used together with OutlierDetection to detect unhealthy endpoints, otherwise has no effect.

key is the label key that the selector applies to.

operator represents a key's relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.

values is an array of string values. If the operator is In or NotIn, the values array must be non-empty. If the operator is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.