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Change scheduler logic from random to round-robin #22430

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Mar 8, 2016
Merged

Change scheduler logic from random to round-robin #22430

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41 changes: 21 additions & 20 deletions plugin/pkg/scheduler/generic_scheduler.go
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Expand Up @@ -20,6 +20,7 @@ import (
"bytes"
"fmt"
"math/rand"
"sort"
"strings"
"sync"

Expand Down Expand Up @@ -55,12 +56,13 @@ func (f *FitError) Error() string {
}

type genericScheduler struct {
predicates map[string]algorithm.FitPredicate
prioritizers []algorithm.PriorityConfig
extenders []algorithm.SchedulerExtender
pods algorithm.PodLister
random *rand.Rand
randomLock sync.Mutex
predicates map[string]algorithm.FitPredicate
prioritizers []algorithm.PriorityConfig
extenders []algorithm.SchedulerExtender
pods algorithm.PodLister
random *rand.Rand
randomLock sync.Mutex
lastNodeIndex uint64
}

// Schedule tries to schedule the given pod to one of node in the node list.
Expand Down Expand Up @@ -109,24 +111,16 @@ func (g *genericScheduler) selectHost(priorityList schedulerapi.HostPriorityList
return "", fmt.Errorf("empty priorityList")
}

sort.Sort(sort.Reverse(priorityList))
maxScore := priorityList[0].Score
// idx contains indices of elements with score == maxScore.
idx := []int{}

for i, entry := range priorityList {
if entry.Score > maxScore {
maxScore = entry.Score
idx = []int{i}
} else if entry.Score == maxScore {
idx = append(idx, i)
}
}
firstAfterMaxScore := sort.Search(len(priorityList), func(i int) bool { return priorityList[i].Score < maxScore })

g.randomLock.Lock()
ix := g.random.Int() % len(idx)
ix := int(g.lastNodeIndex % uint64(firstAfterMaxScore))
g.lastNodeIndex++
g.randomLock.Unlock()

return priorityList[idx[ix]].Host, nil
return priorityList[ix].Host, nil
}

// Filters the nodes to find the ones that fit based on the given predicate functions
Expand Down Expand Up @@ -188,7 +182,14 @@ func findNodesThatFit(pod *api.Pod, nodeNameToInfo map[string]*schedulercache.No
// Each priority function can also have its own weight
// The node scores returned by the priority function are multiplied by the weights to get weighted scores
// All scores are finally combined (added) to get the total weighted scores of all nodes
func PrioritizeNodes(pod *api.Pod, nodeNameToInfo map[string]*schedulercache.NodeInfo, podLister algorithm.PodLister, priorityConfigs []algorithm.PriorityConfig, nodeLister algorithm.NodeLister, extenders []algorithm.SchedulerExtender) (schedulerapi.HostPriorityList, error) {
func PrioritizeNodes(
pod *api.Pod,
nodeNameToInfo map[string]*schedulercache.NodeInfo,
podLister algorithm.PodLister,
priorityConfigs []algorithm.PriorityConfig,
nodeLister algorithm.NodeLister,
extenders []algorithm.SchedulerExtender,
) (schedulerapi.HostPriorityList, error) {
result := schedulerapi.HostPriorityList{}

// If no priority configs are provided, then the EqualPriority function is applied
Expand Down