placement

package

v0.2.0 Latest Latest Go to latest Published: Oct 12, 2026 License: Apache-2.0 Imports: 5 Imported by: 0

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Valid go.mod file
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Repository

github.com/GLINCKER/levelrail

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Documentation ¶

Overview ¶

Package placement is the multi-node scheduler: node label selectors plus a simple spread over eligible nodes. No bin-packing, by design.

Index ¶

Variables
func Check(c Candidate, req Request) error
func Filter(c Candidate, req Request) string
func ParseLabels(pairs []string) (map[string]string, error)
func ValidateLabels(labels map[string]string) error
type Candidate
type Decision
- func Spread(cands []Candidate, req Request) (Decision, error)
type Rejection
type Request
type Selector
- func (sel Selector) Matches(labels map[string]string) bool
- func (sel Selector) String() string

Constants ¶

This section is empty.

Variables ¶

View Source

var ErrNoEligibleNode = errors.New("placement: no eligible node")

ErrNoEligibleNode is returned when no candidate passes every filter.

Functions ¶

func Check ¶

func Check(c Candidate, req Request) error

Check validates an explicit target against req, the manual-assignment path.

func Filter ¶

func Filter(c Candidate, req Request) string

Filter returns why c may not take req, or "" when it may.

func ParseLabels ¶

func ParseLabels(pairs []string) (map[string]string, error)

ParseLabels turns ["k=v", ...] into a validated map.

func ValidateLabels ¶

func ValidateLabels(labels map[string]string) error

ValidateLabels checks keys and values are short, plain identifiers.

Types ¶

type Candidate ¶

type Candidate struct {
	ID          string
	Name        string
	Labels      map[string]string
	Schedulable bool
	Online      bool
	// Load is how many apps and databases already run there.
	Load int
}

Candidate is one node as the scheduler sees it.

type Decision ¶

type Decision struct {
	NodeID   string
	Rejected []Rejection
}

Decision is the chosen node, plus every rejected candidate's reason.

func Spread ¶

func Spread(cands []Candidate, req Request) (Decision, error)

Spread picks the least loaded eligible candidate, ties broken by ID so the choice is deterministic.

type Rejection ¶

type Rejection struct {
	NodeID string `json:"node_id"`
	Reason string `json:"reason"`
}

Rejection says why one candidate was filtered out.

type Request ¶

type Request struct {
	Selector Selector
	// Exclude is skipped outright, typically the node being drained.
	Exclude string
}

Request is what one placement decision needs.

type Selector ¶

type Selector map[string]string

Selector is a set of key=value pairs a node's labels must all carry.

func (Selector) Matches ¶

func (sel Selector) Matches(labels map[string]string) bool

Matches reports whether labels satisfy every pair in sel.

func (Selector) String ¶

func (sel Selector) String() string

String renders sel as sorted "k=v,k=v".

Source Files ¶

View all Source files

placement.go

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