labels

Documentation

Overview

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

Index

• type ByKey
  • func (a ByKey) Len() int
  • func (a ByKey) Less(i, j int) bool
  • func (a ByKey) Swap(i, j int)
• type LabelSelector
  • func (lsel LabelSelector) Empty() bool
  • func (lsel LabelSelector) Matches(l Labels) bool
  • func (lsel LabelSelector) RequiresExactMatch(label string) (value string, found bool)
  • func (lsel LabelSelector) String() string
• type Labels
• type Lexer
  • func (l *Lexer) Lex() (tok Token, lit string)
• type Operator
• type Parser
• type ParserContext
• type Requirement
  • func NewRequirement(key string, op Operator, vals util.StringSet) (*Requirement, error)
  • func (r *Requirement) Matches(ls Labels) bool
  • func (r *Requirement) RequiresExactMatch(label string) (string, bool)
  • func (r *Requirement) String() string
• type ScannedItem
• type Selector
  • func Everything() Selector
  • func OneTermEqualSelector(k, v string) Selector
  • func OneTermEqualSelectorParse(k, v string) Selector
  • func Parse(selector string) (Selector, error)
  • func ParseAndTransformSelector(selector string, fn TransformFunc) (Selector, error)
  • func ParseSelector(selector string) (Selector, error)
  • func SelectorFromSet(ls Set) Selector
  • func SelectorFromSetParse(ls Set) (Selector, error)
• 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 Token
• type TransformFunc

Types

type ByKey

type ByKey []Requirement

Sort by obtain determisitic parser (minimic previous andTerm based stuff)

func (ByKey) Len

func (a ByKey) Len() int

func (ByKey) Less

func (a ByKey) Less(i, j int) bool

func (ByKey) Swap

func (a ByKey) Swap(i, j int)

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.

func (LabelSelector) Empty

func (lsel LabelSelector) Empty() bool

Return true if the LabelSelector doesn't restrict selection space

func (LabelSelector) Matches

func (lsel LabelSelector) Matches(l Labels) bool

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

func (LabelSelector) RequiresExactMatch

func (lsel LabelSelector) RequiresExactMatch(label string) (value string, found 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.

func (LabelSelector) String

func (lsel LabelSelector) String() string

String returns a comma-separated string of all the LabelSelector Requirements' human-readable strings.

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 Lexer

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

Lexer represents the Lexer struct for label selector. It contains necessary informationt to tokenize the input string

func (*Lexer) Lex

func (l *Lexer) Lex() (tok Token, lit string)

Lex returns a pair of Token and the literal literal is meaningfull only for IdentifierToken token

type Operator

type Operator string

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

const (
	EqualsOperator       Operator = "="
	DoubleEqualsOperator Operator = "=="
	InOperator           Operator = "in"
	NotEqualsOperator    Operator = "!="
	NotInOperator        Operator = "notin"
	ExistsOperator       Operator = "exists"
)

type Parser

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

Parser data structure contains the label selector parser data strucutre

type ParserContext

type ParserContext int

Parser context represents context during parsing: some literal for example 'in' and 'notin' can be recognized as operator for example 'x in (a)' but it can be recognized as value for example 'value in (in)'

const (
	KeyAndOperator ParserContext = iota
	Values
)

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. Requirement implements both set based match and exact match Requirement is initialized via NewRequirement constructor for creating a valid Requirement.

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

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.

func (*Requirement) RequiresExactMatch

func (r *Requirement) RequiresExactMatch(label string) (string, 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.

func (*Requirement) String

func (r *Requirement) String() string

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 ScannedItem

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

The item produced by the lexer. It contains the Token and the literal.

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.
	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 OneTermEqualSelectorParse

func OneTermEqualSelectorParse(k, v string) Selector

OneTermEqualSelectorParse: implement OneTermEqualSelector using of LabelSelector and Requirement TODO: remove the original OneTermSelector and rename OneTermEqualSelectorParse to OneTermEqualSelector Since OneTermEqualSelector cannot return an error. the Requirement based version ignore error. it's up to the caller being sure that k and v are not empty

func Parse

func Parse(selector string) (Selector, 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> ::= KEY [ <set-based-restriction> | <exact-match-restriction> <set-based-restriction> ::= "" | <inclusion-exclusion> <value-set> <inclusion-exclusion> ::= <inclusion> | <exclusion>

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

<exact-match-restriction> ::= ["="|"=="|"!="] VALUE KEY is a sequence of one or more characters following [ DNS_SUBDOMAIN "/" ] DNS_LABEL VALUE is a sequence of zero or more characters "([A-Za-z0-9_-\.])". Max length is 64 character. Delimiter is white space: (' ', '\t') 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.

func ParseAndTransformSelector

func ParseAndTransformSelector(selector string, fn TransformFunc) (Selector, error)

Parses the selector and runs them through the given TransformFunc.

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().

func SelectorFromSetParse

func SelectorFromSetParse(ls Set) (Selector, error)

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 Token

type Token int

constants definition for lexer token

const (
	ErrorToken Token = iota
	EndOfStringToken
	ClosedParToken
	CommaToken
	DoubleEqualsToken
	EqualsToken
	IdentifierToken // to represent keys and values
	InToken
	NotEqualsToken
	NotInToken
	OpenParToken
)

type TransformFunc

type TransformFunc func(label, value string) (newLabel, newValue string, err error)

Function to transform selectors.