This API feature is currently work-in-progress. API features marked as work-in-progress are not considered stable, are not covered by the threat model, are not supported by the security team, and are subject to breaking changes. Do not use this feature without understanding each of the previous points.


[.xds.core.v3.ResourceLocator proto]

xDS resource locators identify a xDS resource name and instruct the data-plane load balancer on how the resource may be located.

Resource locators have a canonical xdstp:// URI representation:


where context_params take the form of URI query parameters.

Resource locators have a similar canonical http:// URI representation:


Resource locators also have a simplified file:// URI representation:


  "scheme": "...",
  "id": "...",
  "authority": "...",
  "resource_type": "...",
  "exact_context": "{...}",
  "directives": []

(.xds.core.v3.ResourceLocator.Scheme) URI scheme.


(string) Opaque identifier for the resource. Any ‘/’ will not be escaped during URI encoding and will form part of the URI path. This may end with ‘*’ for glob collection references.


(string) Logical authority for resource (not necessarily transport network address). Authorities are opaque in the xDS API, data-plane load balancers will map them to concrete network transports such as an xDS management server, e.g. via envoy.config.core.v3.ConfigSource.


(string, REQUIRED) Fully qualified resource type (as in type URL without types.googleapis.com/ prefix).


(.xds.core.v3.ContextParams) Additional parameters that can be used to select resource variants. Matches must be exact, i.e. all context parameters must match exactly and there must be no additional context parameters set on the matched resource.


(repeated .xds.core.v3.ResourceLocator.Directive) A list of directives that appear in the xDS resource locator #fragment.

When encoding to URI form, directives are percent encoded with comma separation.


[.xds.core.v3.ResourceLocator.Directive proto]

Directives provide information to data-plane load balancers on how xDS resource names are to be interpreted and potentially further resolved. For example, they may provide alternative resource locators for when primary resolution fails. Directives are not part of resource names and do not appear in a xDS transport discovery request.

When encoding to URIs, directives take the form:

<directive name>=<string representation of directive value>

For example, we can have alt=xdstp://foo/bar or entry=some%20thing. Each directive value type may have its own string encoding, in the case of ResourceLocator there is a recursive URI encoding.

Percent encoding applies to the URI encoding of the directive value. Multiple directives are comma-separated, so the reserved characters that require percent encoding in a directive value are [‘,’, ‘#’, ‘[‘, ‘]’, ‘%’]. These are the RFC3986 fragment reserved characters with the addition of the xDS scheme specific ‘,’. See https://tools.ietf.org/html/rfc3986#page-49 for further details on URI ABNF and reserved characters.

  "alt": "{...}",
  "entry": "..."

(.xds.core.v3.ResourceLocator) An alternative resource locator for fallback if the resource is unavailable. For example, take the resource locator:


If the data-plane load balancer is unable to reach foo to fetch the resource, it will fallback to bar. Alternative resources do not need to have equivalent content, but they should be functional substitutes.

Precisely one of alt, entry must be set.


(string) List collections support inlining of resources via the entry field in Resource. These inlined Resource objects may have an optional name field specified. When specified, the entry directive allows ResourceLocator to directly reference these inlined resources, e.g. xdstp://…/foo#entry=bar.

Precisely one of alt, entry must be set.

Enum .xds.core.v3.ResourceLocator.Scheme

[.xds.core.v3.ResourceLocator.Scheme proto]