--- layout: docs page_title: 'Configuration Entry Kind: Service Resolver' sidebar_title: Service Resolver description: >- The `service-resolver` config entry kind controls which service instances should satisfy Connect upstream discovery requests for a given service name. --- # Service Resolver -> **v1.8.4+:** On Kubernetes, the `ServiceResolver` custom resource is supported in Consul versions 1.8.4+.
**v1.6.0+:** On other platforms, this config entry is supported in Consul versions 1.6.0+. The `service-resolver` config entry kind (`ServiceResolver` on Kubernetes) controls which service instances should satisfy Connect upstream discovery requests for a given service name. If no resolver config is defined the chain assumes 100% of traffic goes to the healthy instances of the default service in the current datacenter+namespace and discovery terminates. ## Interaction with other Config Entries - Service resolver config entries are a component of [L7 Traffic Management](/docs/connect/l7-traffic-management). ## Sample Config Entries ### Filter on service version Create service subsets based on a version metadata and override the defaults: ```hcl Kind = "service-resolver" Name = "web" DefaultSubset = "v1" Subsets = { "v1" = { Filter = "Service.Meta.version == v1" } "v2" = { Filter = "Service.Meta.version == v2" } } ``` Create service subsets based on a version metadata and override the defaults: ```yaml apiVersion: consul.hashicorp.com/v1alpha1 kind: ServiceResolver metadata: name: web spec: defaultSubset: 'v1' subsets: 'v1': filter: 'Service.Meta.version == v1' 'v2': filter: 'Service.Meta.version == v2' ``` ### Other datacenters Expose a set of services in another datacenter as a virtual service: ```hcl Kind = "service-resolver" Name = "web-dc2" Redirect { Service = "web" Datacenter = "dc2" } ``` Expose a set of services in another datacenter as a virtual service: ```yaml apiVersion: consul.hashicorp.com/v1alpha1 kind: ServiceResolver metadata: name: web-dc2 spec: redirect: service: web datacenter: dc2 ``` ### Datacenter failover Enable failover for all subsets: ```hcl Kind = "service-resolver" Name = "web" ConnectTimeout = "15s" Failover = { "*" = { Datacenters = ["dc3", "dc4"] } } ``` Enable failover for all subsets: ```yaml apiVersion: consul.hashicorp.com/v1alpha1 kind: ServiceResolver metadata: name: web spec: connectTimeout: 15s failover: '*': datacenters: ['dc3', 'dc4'] ``` ### Consistent load balancing Apply consistent load balancing for requests based on `x-user-id` header: ```hcl Kind = "service-resolver" Name = "web" LoadBalancer = { Policy = "maglev" HashPolicies = [ { Field = "header" FieldValue = "x-user-id" } ] } ``` Apply consistent load balancing for requests based on `x-user-id` header: ```yaml apiVersion: consul.hashicorp.com/v1alpha1 kind: ServiceResolver metadata: name: web spec: loadBalancer: policy: maglev hashPolicies: - field: header fieldValue: x-user-id ``` ## Available Fields ', yaml: false, }, { name: 'Namespace', type: `string: "default"`, enterprise: true, description: 'Specifies the namespace the config entry will apply to.', yaml: false, }, { name: 'Meta', type: 'map: nil', description: 'Specifies arbitrary KV metadata pairs. Added in Consul 1.8.4.', yaml: false, }, { name: 'metadata', children: [ { name: 'name', description: 'Set to the name of the service being configured.', }, { name: 'namespace', description: 'If running Consul Open Source, the namespace is ignored (see [Kubernetes Namespaces in Consul OSS](/docs/k8s/crds#consul-oss)). If running Consul Enterprise see [Kubernetes Namespaces in Consul Enterprise](/docs/k8s/crds#consul-enterprise) for more details.', }, ], hcl: false, }, { name: 'ConnectTimeout', type: 'duration: 0s', description: 'The timeout for establishing new network connections to this service.', }, { name: 'DefaultSubset', type: 'string: ""', description: 'The subset to use when no explicit subset is requested. If empty the unnamed subset is used.', }, { name: 'Subsets', type: 'map[string]ServiceResolverSubset', description: 'A map of subset name to subset definition for all usable named subsets of this service. The map key is the name of the subset and all names must be valid DNS subdomain elements.

This may be empty, in which case only the unnamed default subset will be usable.', children: [ { name: 'Filter', type: 'string: ""', description: `The [filter expression](/api/features/filtering) to be used for selecting instances of the requested service. If empty all healthy instances are returned. This expression can filter on the same selectors as the [Health API endpoint](/api/health#filtering-2).`, }, { name: 'OnlyPassing', type: 'bool: false', description: `Specifies the behavior of the resolver's health check interpretation. If this is set to false, instances with checks in the passing as well as the warning states will be considered healthy. If this is set to true, only instances with checks in the passing state will be considered healthy.`, }, ], }, { name: 'Redirect', type: 'ServiceResolverRedirect: ', description: { hcl: `When configured, all attempts to resolve the service this resolver defines will be substituted for the supplied redirect EXCEPT when the redirect has already been applied.

When substituting the supplied redirect into the all other fields besides \`Kind\`, \`Name\`, and \`Redirect\` will be ignored.`, yaml: `When configured, all attempts to resolve the service this resolver defines will be substituted for the supplied redirect EXCEPT when the redirect has already been applied.

When substituting the supplied redirect into the all other fields besides \`redirect\` will be ignored.`, }, children: [ { name: 'Service', type: 'string: ""', description: 'A service to resolve instead of the current service.', }, { name: 'ServiceSubset', type: 'string: ""', description: { hcl: `A named subset of the given service to resolve instead of one defined as that service's \`DefaultSubset\`. If empty, the default subset is used.

If this is specified at least one of \`Service\`, \`Datacenter\`, or \`Namespace\` should be configured.`, yaml: `A named subset of the given service to resolve instead of one defined as that service's \`defaultSubset\`. If empty, the default subset is used.

If this is specified at least one of \`service\`, \`datacenter\`, or \`namespace\` should be configured.`, }, }, { name: 'Namespace', enterprise: true, type: 'string: ""', description: 'The namespace to resolve the service from instead of the current one.', }, { name: 'Datacenter', type: 'string: ""', description: 'The datacenter to resolve the service from instead of the current one.', }, ], }, { name: 'Failover', type: 'map[string]ServiceResolverFailover', description: { hcl: `Controls when and how to reroute traffic to an alternate pool of service instances.

The map is keyed by the service subset it applies to and the special string \`"*"\` is a wildcard that applies to any subset not otherwise specified here.

\`Service\`, \`ServiceSubset\`, \`Namespace\`, and \`Datacenters\` cannot all be empty at once.`, yaml: `Controls when and how to reroute traffic to an alternate pool of service instances.

The map is keyed by the service subset it applies to and the special string \`"*"\` is a wildcard that applies to any subset not otherwise specified here.

\`service\`, \`serviceSubset\`, \`namespace\`, and \`datacenters\` cannot all be empty at once.`, }, children: [ { name: 'Service', type: 'string: ""', description: 'The service to resolve instead of the default as the failover group of instances during failover.', }, { name: 'ServiceSubset', type: 'string: ""', description: 'The named subset of the requested service to resolve as the failover group of instances. If empty the default subset for the requested service is used.', }, { name: 'Namespace', enterprise: true, type: 'string: ""', description: 'The namespace to resolve the requested service from to form the failover group of instances. If empty the current namespace is used.', }, { name: 'Datacenters', type: 'array', description: 'A fixed list of datacenters to try during failover.', }, ], }, { name: 'LoadBalancer', type: 'LoadBalancer', description: 'Determines the load balancing policy and configuration for services issuing requests to this upstream. This option is available in Consul versions 1.9.0 and newer.', children: [ { name: 'Policy', type: 'string: ""', description: 'The load balancing policy used to select a host. One of: `random`, `round_robin`, `least_request`, `ring_hash`, `maglev`.', }, { name: 'RingHashConfig', type: 'RingHashConfig', description: 'Configuration for the `ring_hash` policy type.', children: [ { name: 'MinimumRingRize', type: 'int: 1024', description: 'Determines the minimum number of entries in the hash ring.', }, { name: 'MaximumRingRize', type: 'int: 8192', description: 'Determines the maximum number of entries in the hash ring.', }, ], }, { name: 'LeastRequestConfig', type: 'LeastRequestConfig', description: 'Configuration for the `least_request` policy type.', children: [ { name: 'ChoiceCount', type: 'int: 2', description: 'Determines the number of random healthy hosts from which to select the one with the least requests.', }, ], }, { name: 'HashPolicies', type: 'array', description: `List of hash policies to use for hashing load balancing algorithms. Hash policies are evaluated individually and combined such that identical lists result in the same hash. If no hash policies are present, or none are successfully evaluated, then a random backend host will be selected.`, children: [ { name: 'Field', type: 'string: ""', description: { hcl: 'The attribute type to hash on. Must be one of `header`, `cookie`, or `query_parameter`. Cannot be specified along with `SourceAddress`.', yaml: 'The attribute type to hash on. Must be one of `header`, `cookie`, or `query_parameter`. Cannot be specified along with `sourceAddress`.', }, }, { name: 'FieldValue', type: 'string: ""', description: { hcl: 'The value to hash. ie. header name, cookie name, URL query parameter name. Cannot be specified along with `SourceAddress`.', yaml: 'The value to hash. ie. header name, cookie name, URL query parameter name. Cannot be specified along with `sourceAddress`.', }, }, { name: 'CookieConfig', type: 'CookieConfig', description: 'Additional configuration for the "cookie" hash policy type. This is specified to have Envoy generate a cookie for a client on its first request.', children: [ { name: 'Session', type: 'bool: false', description: 'Generates a session cookie with no expiration.', }, { name: 'TTL', type: 'duration: 0s', description: 'TTL for generated cookies. Cannot be specified for session cookies.', }, { name: 'Path', type: 'string: ""', description: 'The path to set for the cookie.', }, ], }, { name: 'SourceIP', type: 'bool: false', description: { hcl: 'Determines whether the hash should be of the source IP address rather than of a field and field value. Cannot be specified along with `Field` or `FieldValue`.', yaml: 'Determines whether the hash should be of the source IP address rather than of a field and field value. Cannot be specified along with `field` or `fieldValue`.', }, }, { name: 'Terminal', type: 'bool: false', description: 'Will short circuit the computation of the hash when multiple hash policies are present. If a hash is computed when a Terminal policy is evaluated, then that hash will be used and subsequent hash policies will be ignored.', }, ], }, ], }, ]} /> ## Service Subsets A service subset assigns a concrete name to a specific subset of discoverable service instances within a datacenter, such as `"version2"` or `"canary"`. A service subset name is useful only when composed with an actual service name, a specific datacenter, and namespace. All services have an unnamed default subset that will return all healthy instances unfiltered. Subsets are defined in `service-resolver` configuration entries, but are referenced by their names throughout the other configuration entry kinds. ## ACLs Configuration entries may be protected by [ACLs](/docs/security/acl). Reading a `service-resolver` config entry requires `service:read` on the resource. Creating, updating, or deleting a `service-resolver` config entry requires `service:write` on the resource and `service:read` on any other service referenced by name in these fields: - [`Redirect.Service`](#service) - [`Failover[].Service`](#service-1)