forked from hashicorp/nomad
/
feasible.go
259 lines (222 loc) · 6.24 KB
/
feasible.go
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package scheduler
import (
"fmt"
"reflect"
"strings"
"github.com/hashicorp/nomad/nomad/structs"
)
// FeasibleIterator is used to iteratively yield nodes that
// match feasibility constraints. The iterators may manage
// some state for performance optimizations.
type FeasibleIterator interface {
// Next yields a feasible node or nil if exhausted
Next() *structs.Node
// Reset is invoked when an allocation has been placed
// to reset any stale state.
Reset()
}
// StaticIterator is a FeasibleIterator which returns nodes
// in a static order. This is used at the base of the iterator
// chain only for testing due to deterministic behavior.
type StaticIterator struct {
ctx Context
nodes []*structs.Node
offset int
seen int
}
// NewStaticIterator constructs a random iterator from a list of nodes
func NewStaticIterator(ctx Context, nodes []*structs.Node) *StaticIterator {
iter := &StaticIterator{
ctx: ctx,
nodes: nodes,
}
return iter
}
func (iter *StaticIterator) Next() *structs.Node {
// Check if exhausted
n := len(iter.nodes)
if iter.offset == n || iter.seen == n {
if iter.seen != n {
iter.offset = 0
} else {
return nil
}
}
// Return the next offset
offset := iter.offset
iter.offset += 1
iter.seen += 1
iter.ctx.Metrics().EvaluateNode()
return iter.nodes[offset]
}
func (iter *StaticIterator) Reset() {
iter.seen = 0
}
func (iter *StaticIterator) SetNodes(nodes []*structs.Node) {
iter.nodes = nodes
iter.offset = 0
iter.seen = 0
}
// NewRandomIterator constructs a static iterator from a list of nodes
// after applying the Fisher-Yates algorithm for a random shuffle. This
// is applied in-place
func NewRandomIterator(ctx Context, nodes []*structs.Node) *StaticIterator {
// shuffle with the Fisher-Yates algorithm
shuffleNodes(nodes)
// Create a static iterator
return NewStaticIterator(ctx, nodes)
}
// DriverIterator is a FeasibleIterator which returns nodes that
// have the drivers necessary to scheduler a task group.
type DriverIterator struct {
ctx Context
source FeasibleIterator
drivers map[string]struct{}
}
// NewDriverIterator creates a DriverIterator from a source and set of drivers
func NewDriverIterator(ctx Context, source FeasibleIterator, drivers map[string]struct{}) *DriverIterator {
iter := &DriverIterator{
ctx: ctx,
source: source,
drivers: drivers,
}
return iter
}
func (iter *DriverIterator) SetDrivers(d map[string]struct{}) {
iter.drivers = d
}
func (iter *DriverIterator) Next() *structs.Node {
for {
// Get the next option from the source
option := iter.source.Next()
if option == nil {
return nil
}
// Use this node if possible
if iter.hasDrivers(option) {
return option
}
iter.ctx.Metrics().FilterNode(option, "missing drivers")
}
}
func (iter *DriverIterator) Reset() {
iter.source.Reset()
}
// hasDrivers is used to check if the node has all the appropriate
// drivers for this task group. Drivers are registered as node attribute
// like "driver.docker=1" with their corresponding version.
func (iter *DriverIterator) hasDrivers(option *structs.Node) bool {
for driver := range iter.drivers {
driverStr := fmt.Sprintf("driver.%s", driver)
_, ok := option.Attributes[driverStr]
if !ok {
return false
}
}
return true
}
// ConstraintIterator is a FeasibleIterator which returns nodes
// that match a given set of constraints. This is used to filter
// on job, task group, and task constraints.
type ConstraintIterator struct {
ctx Context
source FeasibleIterator
constraints []*structs.Constraint
}
// NewConstraintIterator creates a ConstraintIterator from a source and set of constraints
func NewConstraintIterator(ctx Context, source FeasibleIterator, constraints []*structs.Constraint) *ConstraintIterator {
iter := &ConstraintIterator{
ctx: ctx,
source: source,
constraints: constraints,
}
return iter
}
func (iter *ConstraintIterator) SetConstraints(c []*structs.Constraint) {
iter.constraints = c
}
func (iter *ConstraintIterator) Next() *structs.Node {
for {
// Get the next option from the source
option := iter.source.Next()
if option == nil {
return nil
}
// Use this node if possible
if iter.meetsConstraints(option) {
return option
}
}
}
func (iter *ConstraintIterator) Reset() {
iter.source.Reset()
}
func (iter *ConstraintIterator) meetsConstraints(option *structs.Node) bool {
for _, constraint := range iter.constraints {
if !iter.meetsConstraint(constraint, option) {
iter.ctx.Metrics().FilterNode(option, constraint.String())
return false
}
}
return true
}
func (iter *ConstraintIterator) meetsConstraint(constraint *structs.Constraint, option *structs.Node) bool {
// Only enforce hard constraints, soft constraints are used for ranking
if !constraint.Hard {
return true
}
// Resolve the targets
lVal, ok := resolveConstraintTarget(constraint.LTarget, option)
if !ok {
return false
}
rVal, ok := resolveConstraintTarget(constraint.RTarget, option)
if !ok {
return false
}
// Check if satisfied
return checkConstraint(constraint.Operand, lVal, rVal)
}
// resolveConstraintTarget is used to resolve the LTarget and RTarget of a Constraint
func resolveConstraintTarget(target string, node *structs.Node) (interface{}, bool) {
// If no prefix, this must be a literal value
if !strings.HasPrefix(target, "$") {
return target, true
}
// Handle the interpolations
switch {
case "$node.id" == target:
return node.ID, true
case "$node.datacenter" == target:
return node.Datacenter, true
case "$node.name" == target:
return node.Name, true
case strings.HasPrefix(target, "$attr."):
attr := strings.TrimPrefix(target, "$attr.")
val, ok := node.Attributes[attr]
return val, ok
case strings.HasPrefix(target, "$meta."):
meta := strings.TrimPrefix(target, "$meta.")
val, ok := node.Meta[meta]
return val, ok
default:
return nil, false
}
}
// checkConstraint checks if a constraint is satisfied
func checkConstraint(operand string, lVal, rVal interface{}) bool {
switch operand {
case "=", "==", "is":
return reflect.DeepEqual(lVal, rVal)
case "!=", "not":
return !reflect.DeepEqual(lVal, rVal)
case "<", "<=", ">", ">=":
// TODO: Implement
return false
case "contains":
// TODO: Implement
return false
default:
return false
}
}