labels

Documentation

Overview

Package labels implements a simple label system, parsing and matching selectors with sets of labels.

Index

• type LabelSelector
  • func (lsel *LabelSelector) Matches(l Labels) (bool, error)
  • func (lsel *LabelSelector) String() (string, error)
• type Labels
• type Operator
• type Requirement
  • func NewRequirement(key string, op Operator, vals util.StringSet) (*Requirement, error)
  • func (r *Requirement) Matches(ls Labels) (bool, error)
  • func (r *Requirement) String() (string, error)
• type Selector
  • func Everything() Selector
  • func OneTermEqualSelector(k, v string) Selector
  • func ParseSelector(selector string) (Selector, error)
  • func SelectorFromSet(ls Set) Selector
• type Set
  • func (ls Set) AsSelector() Selector
  • func (ls Set) Get(label string) string
  • func (ls Set) Has(label string) bool
  • func (ls Set) String() string
• type SetBasedSelector
  • func Parse(selector string) (SetBasedSelector, error)

Types

type LabelSelector

type LabelSelector struct {
	Requirements []Requirement
}

LabelSelector contains a list of Requirements. LabelSelector is set-based and is distinguished from exact match-based selectors composed of key=value matching conjunctions. TODO: Remove previous sentence when exact match-based selectors are removed.

func (*LabelSelector) Matches

func (lsel *LabelSelector) Matches(l Labels) (bool, error)

Matches for a LabelSelector returns true if all its Requirements match the input Labels. If any Requirement does not match, false is returned. An error is returned if any match attempt between a Requirement and the input Labels returns an error.

func (*LabelSelector) String

func (lsel *LabelSelector) String() (string, error)

String returns a comma-separated string of all the LabelSelector Requirements' human-readable strings. An error is returned if any attempt to get a Requirement's human-readable string returns an error.

type Labels

type Labels interface {
	// Has returns whether the provided label exists.
	Has(label string) (exists bool)

	// Get returns the value for the provided label.
	Get(label string) (value string)
}

Labels allows you to present labels independently from their storage.

type Operator

type Operator int

Operator represents a key's relationship to a set of values in a Requirement.

const (
	In Operator = iota + 1
	NotIn
	Exists
)

type Requirement

type Requirement struct {
	// contains filtered or unexported fields
}

Requirement is a selector that contains values, a key and an operator that relates the key and values. The zero value of Requirement is invalid. See the NewRequirement constructor for creating a valid Requirement. Requirement is set-based and is distinguished from exact match-based selectors composed of key=value matching. TODO: Remove previous sentence when exact match-based selectors are removed.

func NewRequirement

func NewRequirement(key string, op Operator, vals util.StringSet) (*Requirement, error)

NewRequirement is the constructor for a Requirement. If any of these rules is violated, an error is returned: (1) The operator can only be In, NotIn or Exists. (2) If the operator is In or NotIn, the values set must

be non-empty.

(3) The key is invalid due to its length, or sequence

of characters. See validateLabelKey for more details.

The empty string is a valid value in the input values set.

func (*Requirement) Matches

func (r *Requirement) Matches(ls Labels) (bool, error)

Matches returns true if the Requirement matches the input Labels. There is a match in the following cases: (1) The operator is Exists and Labels has the Requirement's key. (2) The operator is In, Labels has the Requirement's key and Labels'

value for that key is in Requirement's value set.

(3) The operator is NotIn, Labels has the Requirement's key and

Labels' value for that key is not in Requirement's value set.

(4) The operator is NotIn and Labels does not have the

Requirement's key.

If called on an invalid Requirement, an error is returned. See NewRequirement for creating a valid Requirement.

func (*Requirement) String

func (r *Requirement) String() (string, error)

String returns a human-readable string that represents this Requirement. If called on an invalid Requirement, an error is returned. See NewRequirement for creating a valid Requirement.

type Selector

type Selector interface {
	// Matches returns true if this selector matches the given set of labels.
	Matches(Labels) bool

	// Empty returns true if this selector does not restrict the selection space.
	Empty() bool

	// RequiresExactMatch allows a caller to introspect whether a given selector
	// requires a single specific label to be set, and if so returns the value it
	// requires.
	// TODO: expand this to be more general
	RequiresExactMatch(label string) (value string, found bool)

	// String returns a human readable string that represents this selector.
	String() string
}

Selector represents a label selector.

func Everything

func Everything() Selector

Everything returns a selector that matches all labels.

func OneTermEqualSelector

func OneTermEqualSelector(k, v string) Selector

OneTermEqualSelector returns an object that matches objects where one label/field equals one value. Cannot return an error.

func ParseSelector

func ParseSelector(selector string) (Selector, error)

ParseSelector takes a string representing a selector and returns an object suitable for matching, or an error.

func SelectorFromSet

func SelectorFromSet(ls Set) Selector

SelectorFromSet returns a Selector which will match exactly the given Set. A nil Set is considered equivalent to Everything().

type Set

type Set map[string]string

Set is a map of label:value. It implements Labels.

func (Set) AsSelector

func (ls Set) AsSelector() Selector

AsSelector converts labels into a selectors.

func (Set) Get

func (ls Set) Get(label string) string

Get returns the value in the map for the provided label.

func (Set) Has

func (ls Set) Has(label string) bool

Has returns whether the provided label exists in the map.

func (Set) String

func (ls Set) String() string

String returns all labels listed as a human readable string. Conveniently, exactly the format that ParseSelector takes.

type SetBasedSelector

type SetBasedSelector interface {
	// Matches returns true if this selector matches the given set of labels.
	Matches(Labels) (bool, error)

	// String returns a human-readable string that represents this selector.
	String() (string, error)
}

TODO Support forward and reverse indexing (#1183, #1348). Eliminate uses of Selector.RequiresExactMatch. TODO rename to Selector after Selector interface above removed

func Parse

func Parse(selector string) (SetBasedSelector, error)

Parse takes a string representing a selector and returns a selector object, or an error. This parsing function differs from ParseSelector as they parse different selectors with different syntaxes. The input will cause an error if it does not follow this form:

<selector-syntax> ::= <requirement> | <requirement> "," <selector-syntax>
    <requirement> ::= WHITESPACE_OPT KEY <set-restriction>
<set-restriction> ::= "" | <inclusion-exclusion> <value-set>

<inclusion-exclusion> ::= <inclusion> | <exclusion>

<exclusion> ::= WHITESPACE "not" <inclusion>
<inclusion> ::= WHITESPACE "in" WHITESPACE
<value-set> ::= "(" <values> ")"
   <values> ::= VALUE | VALUE "," <values>

KEY is a sequence of one or more characters that does not contain ',' or ' '

[^, ]+

VALUE is a sequence of zero or more characters that does not contain ',', ' ' or ')'

[^, )]*

WHITESPACE_OPT is a sequence of zero or more whitespace characters

\s*

WHITESPACE is a sequence of one or more whitespace characters

\s+

Example of valid syntax:

"x in (foo,,baz),y,z not in ()"

Note:

(1) Inclusion - " in " - denotes that the KEY is equal to any of the
    VALUEs in its requirement
(2) Exclusion - " not in " - denotes that the KEY is not equal to any
    of the VALUEs in its requirement
(3) The empty string is a valid VALUE
(4) A requirement with just a KEY - as in "y" above - denotes that
    the KEY exists and can be any VALUE.

TODO: value validation possibly including duplicate value check, restricting certain characters