--- title: Policy and Telemetry Rules overview: Describes the rules used to configure Mixer's policy and telemetry features. location: https://istio.io/docs/reference/config/istio.policy.v1beta1.html layout: protoc-gen-docs number_of_entries: 9 ---

Describes the rules used to configure Mixer’s policy and telemetry features.

## Action

Action describes which Handler to invoke and what data to pass to it for processing.

The following example instructs Mixer to invoke ‘prometheus-handler’ handler and pass it the object constructed using the instance ‘RequestCountByService’.

      handler: prometheus-handler
      instances:
      - RequestCountByService

Field | Type | Description
--- | --- | ---
`handler` | `string` | Required. Fully qualified name of the handler to invoke. Must match the `name` of a Handler.
`instances` | `string[]` | Required. Each value must match the fully qualified name of the Instances. Referenced instances are evaluated by resolving the attributes/literals for all the fields. The constructed objects are then passed to the `handler` referenced within this action.

## AttributeManifest

AttributeManifest describes a set of Attributes produced by some component of an Istio deployment.

Field | Type | Description
--- | --- | ---
`revision` | `string` | Optional. The revision of this document. Assigned by server.
`name` | `string` | Required. Name of the component producing these attributes. This can be the proxy (with the canonical name “istio-proxy”) or the name of an `attributes` kind adapter in Mixer.
`attributes` | `map<string, AttributeManifest.AttributeInfo>` | The set of attributes this Istio component will be responsible for producing at runtime. We map from attribute name to the attribute’s specification. The name of an attribute, which is how attributes are referred to in aspect configuration, must conform to:
    Name = IDENT { SEPARATOR IDENT };
Where `IDENT` must match the regular expression `*a-z*+` and `SEPARATOR` must match the regular expression `[\.-]`. Attribute names must be unique within a single Istio deployment. The set of canonical attributes are described at https://istio.io/docs/reference/attribute-vocabulary.html. Attributes not in that list should be named with a component-specific suffix such as request.count-my.component.

## AttributeManifest.AttributeInfo

AttributeInfo describes the schema of an Istio `Attribute`.

#### Istio Attributes

Istio uses `attributes` to describe runtime activities of Istio services. An Istio attribute carries a specific piece of information about an activity, such as the error code of an API request, the latency of an API request, or the original IP address of a TCP connection. The attributes are often generated and consumed by different services. For example, a frontend service can generate an authenticated user attribute and pass it to a backend service for access control purpose.

To simplify the system and improve developer experience, Istio uses shared attribute definitions across all components. For example, the same authenticated user attribute will be used for logging, monitoring, analytics, billing, access control, auditing. Many Istio components provide their functionality by collecting, generating, and operating on attributes. For example, the proxy collects the error code attribute, and the logging stores it into a log.

#### Design

Each Istio attribute must conform to an `AttributeInfo` in an `AttributeManifest` in the current Istio deployment at runtime. An `AttributeInfo` is used to define an attribute’s metadata: the type of its value and a detailed description that explains the semantics of the attribute type. Each attribute’s name is globally unique; in other words an attribute name can only appear once across all manifests.

The runtime presentation of an attribute is intentionally left out of this specification, because passing attribute using JSON, XML, or Protocol Buffers does not change the semantics of the attribute. Different implementations can choose different representations based on their needs.

#### HTTP Mapping

Because many systems already have REST APIs, it makes sense to define a standard HTTP mapping for Istio attributes that are compatible with typical REST APIs. The design is to map one attribute to one HTTP header, the attribute name and value becomes the HTTP header name and value. The actual encoding scheme will be decided later.

Field | Type | Description
--- | --- | ---
`description` | `string` | Optional. A human-readable description of the attribute’s purpose.
`valueType` | `ValueType` | Required. The type of data carried by this attribute.

## Connection

Connection allows the operator to specify the endpoint for out-of-process infrastructure backend. Connection is part of the handler custom resource and is specified alongside adapter specific configuration.

Field | Type | Description
--- | --- | ---
`address` | `string` | The address of the backend.

## Handler

Handler allows the operator to configure a specific adapter implementation. Each adapter implementation defines its own `params` proto.

In the following example we define a `metrics` handler for the `prometheus` adapter. The example is in the form of a kubernetes resource: * The `metadata.name` is the name of the handler * The `kind` refers to the adapter name * The `spec` block represents adapter-specific configuration as well as the connection information

    ### Sample-1: No connection specified (for compiled in adapters)
    ### Note: if connection information is not specified, the adapter configuration is directly inside
    ### `spec` block. This is going to be DEPRECATED in favor of Sample-2
    apiVersion: "config.istio.io/v1alpha2"
    kind: prometheus
    metadata:
      name: handler
      namespace: istio-system
    spec:
      metrics:
      - name: request_count
        instance_name: requestcount.metric.istio-system
        kind: COUNTER
        label_names:
        - source_service
        - source_version
        - destination_service
        - destination_version
    ---
    ### Sample-2: With connection information (for out-of-process adapters)
    ### Note: Unlike sample-1, the adapter configuration is parallel to `connection` and is nested inside `param` block.
    apiVersion: "config.istio.io/v1alpha2"
    kind: prometheus
    metadata:
      name: handler
      namespace: istio-system
    spec:
      param:
        metrics:
        - name: request_count
          instance_name: requestcount.metric.istio-system
          kind: COUNTER
          label_names:
          - source_service
          - source_version
          - destination_service
          - destination_version
      connection:
        address: localhost:8090
    ---

Field | Type | Description
--- | --- | ---
`name` | `string` | Required. Must be unique in the entire mixer configuration. Used by Actions to refer to this handler.
`adapter` | `string` | Required. The name of a specific adapter implementation. An adapter’s implementation name is typically a constant in its code.
`params` | `google.protobuf.Struct` | Optional. Depends on adapter implementation. Struct representation of a proto defined by the adapter implementation; this varies depending on the value of field `adapter`.
`connection` | `Connection` | Optional. Information on how to connect to the out-of-process adapter. This is used if the adapter is not compiled into Mixer binary and is running as a separate process.

## Instance

An Instance tells Mixer how to create instances for particular template.

Instance is defined by the operator. Instance is defined relative to a known template. Their purpose is to tell Mixer how to use attributes or literals to produce instances of the specified template at runtime.

The following example instructs Mixer to construct an instance associated with template ‘istio.mixer.adapter.metric.Metric’. It provides a mapping from the template’s fields to expressions. Instances produced with this instance can be referenced by Actions using name ‘RequestCountByService’

    - name: RequestCountByService
      template: istio.mixer.adapter.metric.Metric
      params:
        value: 1
        dimensions:
          source: source.service
          destination_ip: destination.ip

Field | Type | Description
--- | --- | ---
`name` | `string` | Required. The name of this instance Must be unique amongst other Instances in scope. Used by Action to refer to an instance produced by this instance.
`template` | `string` | Required. The name of the template this instance creates instances for. The value must match the name of the available template in scope.
`params` | `google.protobuf.Struct` | Required. Depends on referenced template. Struct representation of a proto defined by the template; this varies depending on the value of field `template`.

## Rule

A Rule is a selector and a set of intentions to be executed when the selector is `true`

The following example instructs Mixer to invoke ‘prometheus-handler’ handler for all services and pass it the instance constructed using the ‘RequestCountByService’ instance.

    - match: destination.service == "*"
      actions:
      - handler: prometheus-handler
        instances:
        - RequestCountByService

Field | Type | Description
--- | --- | ---
`match` | `string` | Required. Match is an attribute based predicate. When Mixer receives a request it evaluates the match expression and executes all the associated `actions` if the match evaluates to true. A few example match: an empty match evaluates to `true` `true`, a boolean literal; a rule with this match will always be executed `destination.service == ratings*` selects any request targeting a service whose name starts with “ratings” `attr1 == "20" && attr2 == "30"` logical AND, OR, and NOT are also available
`actions` | `Action[]` | Optional. The actions that will be executed when match evaluates to `true`.

## ValueType

ValueType describes the types that values in the Istio system can take. These are used to describe the type of Attributes at run time, describe the type of the result of evaluating an expression, and to describe the runtime type of fields of other descriptors.

Name | Description
--- | ---
`VALUE_TYPE_UNSPECIFIED` | Invalid, default value.
`STRING` | An undiscriminated variable-length string.
`INT64` | An undiscriminated 64-bit signed integer.
`DOUBLE` | An undiscriminated 64-bit floating-point value.
`BOOL` | An undiscriminated boolean value.
`TIMESTAMP` | A point in time.
`IP_ADDRESS` | An IP address.
`EMAIL_ADDRESS` | An email address.
`URI` | A URI.
`DNS_NAME` | A DNS name.
`DURATION` | A span between two points in time.
`STRING_MAP` | A map string -> string, typically used by headers.

## google.protobuf.Struct

`Struct` represents a structured data value, consisting of fields which map to dynamically typed values. In some languages, `Struct` might be supported by a native representation. For example, in scripting languages like JS a struct is represented as an object. The details of that representation are described together with the proto support for the language.

The JSON representation for `Struct` is JSON object.

Field | Type | Description
--- | --- | ---
`fields` | `map<string, google.protobuf.Value>` | Unordered map of dynamically typed values.