Struct Metadata

pub struct Metadata {
    pub filter_metadata: HashMap<String, Struct>,
    pub typed_filter_metadata: HashMap<String, Any>,
}

Metadata provides additional inputs to filters based on matched listeners, filter chains, routes and endpoints. It is structured as a map, usually from filter name (in reverse DNS format) to metadata specific to the filter. Metadata key-values for a filter are merged as connection and request handling occurs, with later values for the same key overriding earlier values.

An example use of metadata is providing additional values to http_connection_manager in the envoy.http_connection_manager.access_log namespace.

Another example use of metadata is to per service config info in cluster metadata, which may get consumed by multiple filters.

For load balancing, Metadata provides a means to subset cluster endpoints. Endpoints have a Metadata object associated and routes contain a Metadata object to match against. There are some well defined metadata used today for this purpose:

• {"envoy.lb": {"canary": <bool> }} This indicates the canary status of an endpoint and is also used during header processing (x-envoy-upstream-canary) and for stats purposes. [#next-major-version: move to type/metadata/v2]

Fields

filter_metadata: HashMap<String, Struct>

Key is the reverse DNS filter name, e.g. com.acme.widget. The envoy.* namespace is reserved for Envoy’s built-in filters. If both filter_metadata and :ref:typed_filter_metadata <envoy_v3_api_field_config.core.v3.Metadata.typed_filter_metadata> fields are present in the metadata with same keys, only typed_filter_metadata field will be parsed.

typed_filter_metadata: HashMap<String, Any>

Key is the reverse DNS filter name, e.g. com.acme.widget. The envoy.* namespace is reserved for Envoy’s built-in filters. The value is encoded as google.protobuf.Any. If both :ref:filter_metadata <envoy_v3_api_field_config.core.v3.Metadata.filter_metadata> and typed_filter_metadata fields are present in the metadata with same keys, only typed_filter_metadata field will be parsed.

Trait Implementations

impl Clone for Metadata

fn clone(&self) -> Metadata

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Metadata

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Metadata

fn default() -> Self

Returns the “default value” for a type.

impl Message for Metadata

fn encoded_len(&self) -> usize

Returns the encoded length of the message without a length delimiter.

fn clear(&mut self)

Clears the message, resetting all fields to their default.

fn encode(&self, buf: &mut impl BufMut) -> Result<(), EncodeError>

where Self: Sized,

Encodes the message to a buffer.

fn encode_to_vec(&self) -> Vec<u8>

where Self: Sized,

Encodes the message to a newly allocated buffer.

fn encode_length_delimited( &self, buf: &mut impl BufMut, ) -> Result<(), EncodeError>

where Self: Sized,

Encodes the message with a length-delimiter to a buffer.

fn encode_length_delimited_to_vec(&self) -> Vec<u8>

where Self: Sized,

Encodes the message with a length-delimiter to a newly allocated buffer.

fn decode(buf: impl Buf) -> Result<Self, DecodeError>

where Self: Default,

Decodes an instance of the message from a buffer.

fn decode_length_delimited(buf: impl Buf) -> Result<Self, DecodeError>

where Self: Default,

Decodes a length-delimited instance of the message from the buffer.

fn merge(&mut self, buf: impl Buf) -> Result<(), DecodeError>

where Self: Sized,

Decodes an instance of the message from a buffer, and merges it into self.

fn merge_length_delimited(&mut self, buf: impl Buf) -> Result<(), DecodeError>

where Self: Sized,

Decodes a length-delimited instance of the message from buffer, and merges it into self.

impl Name for Metadata

const NAME: &'static str = "Metadata"

Simple name for this Message. This name is the same as it appears in the source .proto file, e.g. FooBar.

const PACKAGE: &'static str = "envoy.config.core.v3"

Package name this message type is contained in. They are domain-like and delimited by ., e.g. google.protobuf.

fn full_name() -> String

Fully-qualified unique name for this Message. It’s prefixed with the package name and names of any parent messages, e.g. google.rpc.BadRequest.FieldViolation. By default, this is the package name followed by the message name. Fully-qualified names must be unique within a domain of Type URLs.

fn type_url() -> String

Type URL for this Message, which by default is the full name with a leading slash, but may also include a leading domain name, e.g. type.googleapis.com/google.profile.Person. This can be used when serializing into the google.protobuf.Any type.

impl PartialEq for Metadata

fn eq(&self, other: &Metadata) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Metadata