Metaresources and Policy Attachment

The Gateway API defines a Kubernetes object that augments the behavior of an object in a standard way as a Metaresource. ReferenceGrant is an example of this general type of metaresource, but it is far from the only one.

This document also defines a concept called Policy Attachment, which augments the behavior of an object to add additional settings that can't be described within the spec of that object.

Why have this class of attachment? Well, while features like timeouts, retries, and custom health checks are present in most implementations, their details vary since there are no standards (RFCs) around them. This makes these features less portable. So instead of pulling these into the API, we offer a middle ground: a standard way to plug these features in the API and offer a uniform UX across implementations. This standard approach for policy attachment allows implementations to create their own custom policy resources that can essentially extend Gateway API, and have those settings flow across multiple resources (like attaching a Policy to a Gateway and having the settings affect all HTTPRoutes attached to that Gateway, for example).

This document defines how we control the creation of configuration in the underlying Gateway data plane using two types of Policy Attachment.

A "Policy Attachment" is a specific type of metaresource that can affect specific settings across either one object (this is "Direct Policy Attachment"), or objects in a hierarchy (this is "Inherited Policy Attachment").

In either case, a Policy may either affect an object by controlling the value of one of the existing fields in the spec of an object, or it may add additional fields that are not in the spec of the object.

Direct Policy Attachment

A Direct Policy Attachment is tightly bound to one instance of a particular Kind within a single namespace (or to an instance of a single Kind at cluster scope), and only modifies the behavior of the object that matches its binding.

As an example, one use case that Gateway API currently does not support is how to configure details of the TLS required to connect to a backend (in other words, if the process running inside the backend workload expects TLS, not that some automated infrastructure layer is provisioning TLS as in the Mesh case).

A hypothetical TLSConnectionPolicy that targets a Service could be used for this, using the functionality of the Service as describing a set of endpoints. (It should also be noted this is not the only way to solve this problem, just an example to illustrate Direct Policy Attachment.)

The TLSConnectionPolicy would look something like this:

apiVersion: gateway.networking.k8s.io/v1alpha2
kind: TLSConnectionPolicy
metadata:
  name: tlsport8443
  namespace: foo
spec:
  targetRef: # This struct is defined as part of Gateway API
    group: "" # Empty string means core - this is a standard convention
    kind: Service
    name: fooService
  tls:
    certificateAuthorityRefs:
      - name: CAcert
    port: 8443

All this does is tell an implementation, that for connecting to port 8443 on the Service fooService, it should assume that the connection is TLS, and expect the service's certificate to be validated by the chain in the CAcert Secret.

Importantly, this would apply to every usage of that Service across any HTTPRoutes in that namespace, which could be useful for a Service that is reused in a lot of HTTPRoutes.

With these two examples in mind, here are some guidelines for when to consider using Direct Policy Attachment:

• The number or scope of objects to be modified is limited or singular. Direct Policy Attachments must target one specific object.
• The modifications to be made to the objects don’t have any transitive information - that is, the modifications only affect the single object that the targeted metaresource is bound to, and don’t have ramifications that flow beyond that object.
• In terms of status, it should be reasonably easy for a user to understand that everything is working - basically, as long as the targeted object exists, and the modifications are valid, the metaresource is valid, and this should be straightforward to communicate in one or two Conditions. Note that at the time of writing, this is not completed.
• Direct Policy Attachment should only be used to target objects in the same namespace as the Policy object. Allowing cross-namespace references brings in significant security concerns, and/or difficulties about merging cross-namespace policy objects. Notably, Mesh use cases may need to do something like this for consumer policies, but in general, Policy objects that modify the behavior of things outside their own namespace should be avoided unless it uses a handshake of some sort, where the things outside the namespace can opt–out of the behavior. (Notably, this is the design that we used for ReferenceGrant).

Inherited Policy Attachment: It's all about the defaults and overrides

Because an Inherited Policy is a metaresource, it targets some other resource and augments its behavior.

But why have this distinct from other types of metaresource? Because Inherited Policy resources are designed to have a way for settings to flow down a hierarchy.

Defaults set the default value for something, and can be overridden by the “lower” objects (like a connection timeout default policy on a Gateway being overridable inside a HTTPRoute), and Overrides cannot be overridden by “lower” objects (like setting a maximum client timeout to some non-infinite value at the Gateway level to stop HTTPRoute owners from leaking connections over time).

Here are some guidelines for when to consider using an Inherited Policy object:

• The settings or configuration are bound to one containing object, but affect other objects attached to that one (for example, affecting HTTPRoutes attached to a single Gateway, or all HTTPRoutes in a GatewayClass).
• The settings need to able to be defaulted, but can be overridden on a per-object basis.
• The settings must be enforced by one persona, and not modifiable or removable by a lesser-privileged persona. (The owner of a GatewayClass may want to restrict something about all Gateways in a GatewayClass, regardless of who owns the Gateway, or a Gateway owner may want to enforce some setting across all attached HTTPRoutes).
• In terms of status, a good accounting for how to record that the Policy is attached is easy, but recording what resources the Policy is being applied to is not, and needs to be carefully designed to avoid fanout apiserver load. (This is not built at all in the current design either).

When multiple Inherited Policies are used, they can interact in various ways, which are governed by the following rules, which will be expanded on later in in this document.

• If a Policy does not affect an object's fields directly, then the resultant Policy should be the set of all distinct fields inside the relevant Policy objects, as set out by the rules below.
• For Policies that affect an object's existing fields, multiple instances of the same Policy Kind affecting an object's fields will be evaluated as though only a single Policy "wins" the right to affect each field. This operation is performed on a per-distinct-field basis.
• Settings in overrides stanzas will win over the same setting in a defaults stanza.
• overrides settings operate in a "less specific beats more specific" fashion - Policies attached higher up the hierarchy will beat the same type of Policy attached further down the hierarchy.
• defaults settings operate in a "more specific beats less specific" fashion - Policies attached lower down the hierarchy will beat the same type of Policy attached further up the hierarchy.
• For defaults, the most specific value is the one inside the object that the Policy applies to; that is, if a Policy specifies a default, and an object specifies a value, the object's value will win.
• Policies interact with the fields they are controlling in a "replace value" fashion.
• For fields where the value is a scalar, (like a string or a number) should have their value replaced by the value in the Policy if it wins. Notably, this means that a default will only ever replace an empty or unset value in an object.
• For fields where the value is an object, the Policy should include the fields in the object in its definition, so that the replacement can be on simple fields rather than complex ones.
• For fields where the final value is non-scalar, but is not an object with fields of its own, the value should be entirely replaced, not merged. This means that lists of strings or lists of ints specified in a Policy will overwrite the empty list (in the case of a default) or any specified list (in the case of an override). The same applies to map[string]string fields. An example here would be a field that stores a map of annotations - specifying a Policy that overrides annotations will mean that a final object specifying those annotations will have its value entirely replaced by an override setting.
• In the case that two Policies of the same type specify different fields, then all of the specified fields should take effect on the affected object.

Examples to further illustrate these rules are given below.

Policy Attachment for Ingress

Attaching policy to Gateway resources for ingress use cases is relatively straightforward. A policy can reference the resource it wants to apply to. Access is granted with RBAC - for example, anyone that has access to create a RetryPolicy in a given namespace can attach it to any resource within that namespace.

To build on that example, it’s possible to attach policies to more resources. Each policy applies to the referenced resource and everything below it in terms of hierarchy. Although this example is likely more complex than many real world use cases, it helps demonstrate how policy attachment can work across namespaces.

Policy Attachment for Mesh

Although there is a great deal of overlap between ingress and mesh use cases, mesh enables more complex policy attachment scenarios. For example, users may want to apply policy to requests from a specific namespace to a backend in another namespace.

Policy attachment can be quite simple with mesh. Policy can be applied to any resource in any namespace but it can only apply to requests from the same namespace if the target is in a different namespace.

At the other extreme, policy can be used to apply to requests from a specific workload to a backend in another namespace. A route can be used to intercept these requests and split them between different backends (foo-a and foo-b in this case).

Target Reference API

Each Policy resource MUST include a single targetRef field. It MUST not target more than one resource at a time, but it can be used to target larger resources such as Gateways or Namespaces that may apply to multiple child resources.

The targetRef field MUST be an exact replica of the PolicyTargetReference struct included in the Gateway API. Where possible, it is recommended to use that struct directly instead of duplicating the type.

Policy Boilerplate

The following (or something like it) SHOULD be used as for any Policy resource using this API pattern. Within the spec, policy resources that omit both Override and Default fields are defined as Direct Policy Attachment, and Inherited Policy Attachment must include one or both.

// ACMEServicePolicy provides a way to apply Service policy configuration with
// the ACME implementation of the Gateway API.
type ACMEServicePolicy struct {
    metav1.TypeMeta   `json:",inline"`
    metav1.ObjectMeta `json:"metadata,omitempty"`

    // Spec defines the desired state of ACMEServicePolicy.
    Spec ACMEServicePolicySpec `json:"spec"`

    // Status defines the current state of ACMEServicePolicy.
    Status ACMEServicePolicyStatus `json:"status,omitempty"`
}

// ACMEServicePolicySpec defines the desired state of ACMEServicePolicy.
type ACMEServicePolicySpec struct {
    // TargetRef identifies an API object to apply policy to.
    TargetRef gatewayv1a2.PolicyTargetReference `json:"targetRef"`

    // Override defines policy configuration that should override policy
    // configuration attached below the targeted resource in the hierarchy.
    // +optional
    Override *ACMEPolicyConfig `json:"override,omitempty"`

    // Default defines default policy configuration for the targeted resource.
    // +optional
    Default *ACMEPolicyConfig `json:"default,omitempty"`
}

// ACMEPolicyConfig contains ACME policy configuration.
type ACMEPolicyConfig struct {
    // Add configurable policy here
}

// ACMEServicePolicyStatus defines the observed state of ACMEServicePolicy.
type ACMEServicePolicyStatus struct {
    // Conditions describe the current conditions of the ACMEServicePolicy.
    //
    // +optional
    // +listType=map
    // +listMapKey=type
    // +kubebuilder:validation:MaxItems=8
    Conditions []metav1.Condition `json:"conditions,omitempty"`
}

Hierarchy

Each Inherited policy MUST include default and/or override values. Overrides enable admins to enforce policy from the top down. Defaults enable app owners to provide default values from the bottom up for each individual application.

To illustrate this, consider 3 resources with the following hierarchy: A (highest) > B > C. When attaching the concept of defaults and overrides to that, the hierarchy would be expanded to this:

A override > B override > C override > C default > B default > A default.

Note that the hierarchy is reversed for defaults. The rationale here is that overrides usually need to be enforced top down while defaults should apply to the lowest resource first. For example, if an admin needs to attach required policy, they can attach it as an override to a Gateway. That would have precedence over Routes and Services below it. On the other hand, an app owner may want to set a default timeout for their Service. That would have precedence over defaults attached at higher levels such as Route or Gateway.

If using defaults and overrides, each policy resource MUST include 2 structs within the spec. One with override values and the other with default values.

In the following example, the policy attached to the Gateway requires cdn to be enabled and provides some default configuration for that. The policy attached to the Route changes the value for one of those fields (includeQueryString).

kind: AcmeServicePolicy # Example of implementation specific policy name
spec:
  override:
    cdn:
      enabled: true
  default:
    cdn:
      cachePolicy:
        includeHost: true
        includeProtocol: true
        includeQueryString: true
  targetRef:
    kind: Gateway
    name: example
---
kind: AcmeServicePolicy
spec:
  default:
    cdn:
      cachePolicy:
        includeQueryString: false
  targetRef:
    kind: HTTPRoute
    name: example

In this final example, we can see how the override attached to the Gateway has precedence over the default drainTimeout value attached to the Route. At the same time, we can see that the default connectionTimeout attached to the Route has precedence over the default attached to the Gateway.

Also note how the different resources interact - fields that are not common across objects may both end up affecting the final object.

Supported Resources

It is important to note that not every implementation will be able to support policy attachment to each resource described in the hierarchy above. When that is the case, implementations MUST clearly document which resources a policy may be attached to.

Attaching Policy to GatewayClass

GatewayClass may be the trickiest resource to attach policy to. Policy attachment relies on the policy being defined within the same scope as the target. This ensures that only users with write access to a policy resource in a given scope will be able to modify policy at that level. Since GatewayClass is a cluster scoped resource, this means that any policy attached to it must also be cluster scoped.

GatewayClass parameters provide an alternative to policy attachment that may be easier for some implementations to support. These parameters can similarly be used to set defaults and requirements for an entire GatewayClass.

Targeting External Services

In some cases (likely limited to mesh or egress) users may want to apply policies to requests to external services. To accomplish this, implementations can choose to support a reference to a virtual resource type:

apiVersion: networking.example.net/v1alpha1
kind: RetryPolicy
metadata:
  name: foo
spec:
  maxRetries: 5
  targetRef:
    group: networking.example.net
    kind: ExternalService
    name: foo.com

Because this CRD does not have a defaults or overrides section, it is a Direct Attached Policy.

Merging into existing spec fields

It's possible (even likely) that configuration in a Policy may need to be merged into an existing object's fields somehow, particularly for Inherited policies.

When merging into an existing fields inside an object, Policy objects should merge values at a scalar level, not at a struct or object level.

For example, in the CDNCachingPolicy example above, the cdn struct contains a cachePolicy struct that contains fields. If an implementation was merging this configuration into an existing object that contained the same fields, it should merge the fields at a scalar level, with the includeHost, includeProtocol, and includeQueryString values being defaulted if they were not specified in the object being controlled. Similarly, for overrides, the values of the innermost scalar fields should overwrite the scalar fields in the affected object.

Implementations should not copy any structs from the Policy object directly into the affected object, any fields that are overridden should be overridden on a per-field basis.

In the case that the field in the Policy affects a struct that is a member of a list, each existing item in the list in the affected object should have each of its fields compared to the corresponding fields in the Policy.

For non-scalar field values, like a list of strings, or a map[string]string value, the entire value must be overwritten by the value from the Policy. No merging should take place. This mainly applies to overrides, since for defaults, there should be no value present in a field on the final object.

This table shows how this works for various types:

Type	Object config	Override Policy config	Result
string	key: "foo"	key: "bar"	key: "bar"
list	key: ["a","b"]	key: ["c","d"]	key: ["c","d"]
map[string]string	key: {"foo": "a", "bar": "b"}	key: {"foo": "c", "bar": "d"}	key: {"foo": "c", "bar": "d"}

Conflict Resolution

It is possible for multiple policies to target the same object and the same fields inside that object. If multiple policy resources target the same resource and have an identical field specified with different values, precedence MUST be determined in order of the following criteria, continuing on ties:

• Direct Policies should never overlap Inherited Policies. If preventing settings from being overwritten is important, implementations should only use Inherited Policies, and the override stanza that implies.
• Inside Inherited Policies, the same setting in overrides beats the one in defaults.
• The oldest Policy based on creation timestamp. For example, a Policy with a creation timestamp of "2021-07-15 01:02:03" is given precedence over a Policy with a creation timestamp of "2021-07-15 01:02:04".
• The Policy appearing first in alphabetical order by {namespace}/{name}. For example, foo/bar is given precedence over foo/baz.

For a better user experience, a validating webhook can be implemented to prevent these kinds of conflicts all together.

Status

In the current iteration of this design, metaresources and Policy objects don't have any standard way to record what they're attaching to, or applying settings to in the case of Policy Attachment. Previous experience in the Kubernetes API has made it clear that having a single object that can cause status updates to occur across many other objects can have a big performance impact, so the status design must be very carefully done to avoid these kind of fanout problems.

However, the whole purpose of having a standardized Policy API structure and patterns is intended to make this problem solvable both for human users and with tooling.

This is currently a very open question. A discussion is ongoing at #1531, and this GEP will be updated with any outcomes.

Some key concerns that we need to solve for status:

• When multiple controllers are implementing the same Route and recognize a policy, it must be possible to determine which controller was responsible for adding that policy reference to status.
• For this to be somewhat scalable, we must limit the number of status updates that can result from a metaresource update.
• Since we only control some of the resources a policy might be attached to, adding policies to status would only be possible on Gateway API resources, not Services or other kinds of backends.

Interaction with Custom Route Filters

Both Policy attachment and custom Route filters provide ways to extend Gateway API. Although similar in nature, they have slightly different purposes.

Custom Route filters provide a way to configure request/response modifiers or middleware embedded inside Route rules or backend references.

Policy attachment is more broad in scope. In contrast with filters, policies can be attached to a wide variety of Gateway API resources, and include a concept of inherited defaulting and overrides. Although Policy attachment can be used to target an entire Route or Backend, it cannot currently be used to target specific Route rules or backend references. If there are sufficient use cases for this, policy attachment may be expanded in the future to support this fine grained targeting.

The following guidance should be considered when introducing a custom field into any Gateway controller implementation:

1. Use core or extended fields if available

For any given field that a Gateway controller implementation needs, the possibility of using core or extended fields should always be considered before using custom policy resources. This is encouraged to promote standardization and, over time, to absorb capabilities into the API as first class fields, which offer a more streamlined UX than custom policy attachment.

2. Custom filters and policies should only overlap if necessary

Although it's possible that arbitrary fields could be supported by custom policy, custom route filters, and core/extended fields concurrently, it is recommended that implementations only use multiple mechanisms for representing the same fields when those fields really need the defaulting and/or overriding behavior that Policy Attachment provides. For example, a custom filter that allowed the configuration of Authentication inside a HTTPRoute object might also have an associated Policy resource that allowed the filter's settings to be defaulted or overridden. It should be noted that doing this in the absence of a solution to the status problem is likely to be very difficult to troubleshoot.

Conformance Level

This policy attachment pattern is associated with an "EXTENDED" conformance level. The implementations that support this policy attachment model will have the same behavior and semantics, although they may not be able to support attachment of all types of policy at all potential attachment points. When that is the case, implementations MUST clearly document which resources a policy may be attached to.

Examples

This section provides some examples of various types of Policy objects, and how merging, defaults, overrides, and other interactions work.

Direct Policy Attachment

The following Policy sets the minimum TLS version required on a Gateway Listener:

apiVersion: networking.example.io/v1alpha1
kind: TLSMinimumVersionPolicy
metadata:
  name: minimum12
  namespace: appns
spec:
  minimumTLSVersion: 1.2
  targetRef:
    name: internet
    group: gateway.networking.k8s.io
    kind: Gateway

Note that because there is no version controlling the minimum TLS version in the Gateway spec, this is an example of a Policy that affects fields that aren't represented in the object.

Inherited Policy Attachment

It also could be useful to be able to default the minimumTLSVersion setting across multiple Gateways.

This version of the above Policy allows this:

apiVersion: networking.example.io/v1alpha1
kind: TLSMinimumVersionPolicy
metadata:
  name: minimum12
  namespace: appns
spec:
  defaults:
    minimumTLSVersion: 1.2
  targetRef:
    name: appns
    group: ""
    kind: namespace

This Inherited Policy is using the implicit hierarchy that all resources belong to a namespace, so attaching a Policy to a namespace means affecting all possible resources in a namespace. Multiple hierarchies are possible, even within Gateway API, for example Gateway -> Route, Gateway -> Route -> Backend, Gateway -> Route -> Service. GAMMA Policies could conceivably use a hierarchy of Service -> Route as well.

Note that this will not be very discoverable for Gateway owners in the absence of a solution to the Policy status problem.

Conceivably, a security or admin team may want to force Gateways to have at least a minimum TLS version of 1.2 - that would be a job for overrides, like so:

apiVersion: networking.example.io/v1alpha1
kind: TLSMinimumVersionPolicy
metadata:
  name: minimum12
  namespace: appns
spec:
  overrides:
    minimumTLSVersion: 1.2
  targetRef:
    name: appns
    group: ""
    kind: namespace

This will make it so that all Gateways in the default namespace must use a minimum TLS version of 1.2, and this cannot be changed by Gateway owners. Only the Policy owner can change this Policy.

Handling non-scalar values

In this example, we will assume that at some future point, HTTPRoute has grown a Filter to configure retries (RetryFilter), including a field called retryOn that reflects the HTTP status codes that should be retried. The value of this field is a list of strings, being the HTTP codes that must be retried. The retryOn field has no defaults in the field definitions (which is probably a bad design, but we need to show this interaction somehow!)

We also assume that an Inherited RetryOnPolicy exists that allows both defaulting and overriding of the retryOn field in the RetryFilter.

A full RetryOnPolicy to default the field to the codes 501, 502, and 503 would look like this:

apiVersion: networking.example.io/v1alpha1
kind: RetryOnPolicy
metadata:
  name: retryon5xx
  namespace: appns
spec:
  defaults:
    retryOn:
      - "501"
      - "502"
      - "503"
  targetRef:
    kind: Gateway
    group: gateway.networking.k8s.io
    name: we-love-retries

This means that, for HTTPRoutes that use the RetryFilter and do _NOT_ explicitly set this field to something else, (in other words, they contain an empty list), then the field will be set to a list containing501,502, and503`. (Notably, because of Go zero values, this would also occur if the user explicitly set the value to the empty list.)

However, if a HTTPRoute owner sets any value other than the empty list in the filter, then that value will remain, and the Policy will have no effect. These values are not merged.

If the Policy used overrides instead:

apiVersion: networking.example.io/v1alpha1
kind: RetryOnPolicy
metadata:
  name: retryon5xx
  namespace: appns
spec:
  overrides:
    retryOn:
      - "501"
      - "503"
  targetRef:
    kind: Gateway
    group: gateway.networking.k8s.io
    name: you-must-retry

Then no matter what the value is in the filter, it will be set to 501, 503 by the Policy override.

Interactions between defaults, overrides, and field values

All HTTPRoutes that attach to the YouMustRetry Gateway and use a RetryFilter will have any value overwritten by this policy. The empty list, or any number of values, will all be replaced with 501, 502, and 503.

Now, let's also assume that we use the Namespace -> Gateway hierarchy on top of the Gateway -> HTTPRoute hierarchy, and allow attaching a RetryOnPolicy to a namespace. The expectation here is that this will affect all Gateways in a namespace and all HTTPRoutes that use the RetryFilter and attach to those Gateways. (Note that the HTTPRoutes themselves may not necessarily be in the same namespace though.)

If we apply the default policy from earlier to the namespace:

apiVersion: networking.example.io/v1alpha1
kind: RetryOnPolicy
metadata:
  name: retryon5xx
  namespace: appns
spec:
  defaults:
    retryOn:
      - "501"
      - "502"
      - "503"
  targetRef:
    kind: Namespace
    group: ""
    name: appns

Then this will have the same effect as applying that Policy to every Gateway in the default namespace - namely that every HTTPRoute that attaches to every Gateway will have its retryOn field in the RetryFilter set to 501, 502, 503, if there is no other setting in the RetryFilter itself.

With two layers in the hierarchy, we have a more complicated set of interactions possible.

Let's look at some tables for a particular HTTPRoute, assuming that it does not configure the retryOn field, but does configure a RetryFilter, for various types of Policy at different levels.

Overrides interacting with defaults for RetryOnPolicy, empty list in RetryFilter

	None	Namespace override	Gateway override	HTTPRoute override
No default	Empty list	Namespace override	Gateway override Policy	HTTPRoute override
Namespace default	Namespace default	Namespace override	Gateway override	HTTPRoute override
Gateway default	Gateway default	Namespace override	Gateway override	HTTPRoute override
HTTPRoute default	HTTPRoute default	Namespace override	Gateway override	HTTPRoute override

Overrides interacting with other overrides for RetryOnPolicy, empty list in RetryFilter

	No override	Namespace override A	Gateway override A	HTTPRoute override A
No override	Empty list	Namespace override	Gateway override	HTTPRoute override
Namespace override B	Namespace override B	Namespace override first created wins otherwise first alphabetically	Namespace override B	Namespace override B
Gateway override B	Gateway override B	Namespace override A	Gateway override first created wins otherwise first alphabetically	Gateway override B
HTTPRoute override B	HTTPRoute override B	Namespace override A	Gateway override A	HTTPRoute override first created wins otherwise first alphabetically

Defaults interacting with other defaults for RetryOnPolicy, empty list in RetryFilter

	No default	Namespace default A	Gateway default A	HTTPRoute default A
No default	Empty list	Namespace default	Gateway default	HTTPRoute default A
Namespace default B	Namespace default B	Namespace default first created wins otherwise first alphabetically	Gateway default A	HTTPRoute default A
Gateway default B	Gateway default B	Gateway default B	Gateway default first created wins otherwise first alphabetically	HTTPRoute default A
HTTPRoute default B	HTTPRoute default B	HTTPRoute default B	HTTPRoute default B	HTTPRoute default first created wins otherwise first alphabetically

Now, if the HTTPRoute does specify a value in its RetryFilter, it's a bit easier, because we can basically disregard all defaults:

Overrides interacting with defaults for RetryOnPolicy, value in RetryFilter

	None	Namespace override	Gateway override	HTTPRoute override
No default	Value in RetryFilter	Namespace override	Gateway override	HTTPRoute override
Namespace default	Value in RetryFilter	Namespace override	Gateway override	HTTPRoute override
Gateway default	Value in RetryFilter	Namespace override	Gateway override	HTTPRoute override
HTTPRoute default	Value in RetryFilter	Namespace override	Gateway override	HTTPRoute override

Overrides interacting with other overrides for RetryOnPolicy, value in RetryFilter

	No override	Namespace override A	Gateway override A	HTTPRoute override A
No override	Value in RetryFilter	Namespace override A	Gateway override A	HTTPRoute override A
Namespace override B	Namespace override B	Namespace override first created wins otherwise first alphabetically	Namespace override B	Namespace override B
Gateway override B	Gateway override B	Namespace override A	Gateway override first created wins otherwise first alphabetically	Gateway override B
HTTPRoute override B	HTTPRoute override B	Namespace override A	Gateway override A	HTTPRoute override first created wins otherwise first alphabetically

Defaults interacting with other defaults for RetryOnPolicy, value in RetryFilter

	No default	Namespace default A	Gateway default A	HTTPRoute default A
No default	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter
Namespace default B	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter
Gateway default B	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter
HTTPRoute default B	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter	Value in RetryFilter