metadata

Documentation

Index

• func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context
• func NewIncomingContext(ctx context.Context, md MD) context.Context
• func NewOutgoingContext(ctx context.Context, md MD) context.Context
• func ValueFromIncomingContext(ctx context.Context, key string) []string
• type MD
  • func FromIncomingContext(ctx context.Context) (MD, bool)
  • func FromOutgoingContext(ctx context.Context) (MD, bool)
  • func Join(mds ...MD) MD
  • func New(m map[string]string) MD
  • func Pairs(kv ...string) MD
  • func (md MD) Append(k string, vals ...string)
  • func (md MD) Copy() MD
  • func (md MD) Delete(k string)
  • func (md MD) Get(k string) []string
  • func (md MD) Len() int
  • func (md MD) Set(k string, vals ...string)

Functions

func AppendToOutgoingContext

func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context

AppendToOutgoingContext returns a new context with the provided kv merged with any existing metadata in the context. Please refer to the documentation of Pairs for a description of kv.

func NewIncomingContext

func NewIncomingContext(ctx context.Context, md MD) context.Context

NewIncomingContext creates a new context with incoming md attached. md must not be modified after calling this function.

func NewOutgoingContext

func NewOutgoingContext(ctx context.Context, md MD) context.Context

NewOutgoingContext creates a new context with outgoing md attached. If used in conjunction with AppendToOutgoingContext, NewOutgoingContext will overwrite any previously-appended metadata. md must not be modified after calling this function.

func ValueFromIncomingContext

func ValueFromIncomingContext(ctx context.Context, key string) []string

ValueFromIncomingContext returns the metadata value corresponding to the metadata key from the incoming metadata if it exists. Keys are matched in a case insensitive manner.

Types

type MD

type MD map[string][]string

MD is a mapping from metadata keys to values. Users should use the following two convenience functions New and Pairs to generate MD.

func FromIncomingContext

func FromIncomingContext(ctx context.Context) (MD, bool)

FromIncomingContext returns the incoming metadata in ctx if it exists.

All keys in the returned MD are lowercase.

func FromOutgoingContext

func FromOutgoingContext(ctx context.Context) (MD, bool)

FromOutgoingContext returns the outgoing metadata in ctx if it exists.

All keys in the returned MD are lowercase.

func Join

func Join(mds ...MD) MD

Join joins any number of mds into a single MD.

The order of values for each key is determined by the order in which the mds containing those values are presented to Join.

func New

func New(m map[string]string) MD

New creates an MD from a given key-value map.

Only the following ASCII characters are allowed in keys:

• digits: 0-9
• uppercase letters: A-Z (normalized to lower)
• lowercase letters: a-z
• special characters: -_.

Uppercase letters are automatically converted to lowercase.

func Pairs

func Pairs(kv ...string) MD

Pairs returns an MD formed by the mapping of key, value ... Pairs panics if len(kv) is odd.

Only the following ASCII characters are allowed in keys:

• digits: 0-9
• uppercase letters: A-Z (normalized to lower)
• lowercase letters: a-z
• special characters: -_.

Uppercase letters are automatically converted to lowercase.

func (MD) Append

func (md MD) Append(k string, vals ...string)

Append adds the values to key k, not overwriting what was already stored at that key.

k is converted to lowercase before storing in md.

func (MD) Copy

func (md MD) Copy() MD

Copy returns a copy of md.

func (MD) Delete

func (md MD) Delete(k string)

Delete removes the values for a given key k which is converted to lowercase before removing it from md.

func (MD) Get

func (md MD) Get(k string) []string

Get obtains the values for a given key.

k is converted to lowercase before searching in md.

func (MD) Len

func (md MD) Len() int

Len returns the number of items in md.

func (MD) Set

func (md MD) Set(k string, vals ...string)

Set sets the value of a given key with a slice of values.

k is converted to lowercase before storing in md.