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scheduler.go
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scheduler.go
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/*
Copyright 2014 CoreOS, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package engine
import (
"fmt"
"sort"
"github.com/coreos/fleet/agent"
"github.com/coreos/fleet/job"
)
type decision struct {
machineID string
}
type Scheduler interface {
Decide(*clusterState, *job.Job) (*decision, error)
}
type leastLoadedScheduler struct{}
func (lls *leastLoadedScheduler) Decide(clust *clusterState, j *job.Job) (*decision, error) {
agents := lls.sortedAgents(clust)
if len(agents) == 0 {
return nil, fmt.Errorf("zero agents available")
}
var target *agent.AgentState
for _, as := range agents {
if able, _ := as.AbleToRun(j); !able {
continue
}
as := as
target = as
break
}
if target == nil {
return nil, fmt.Errorf("no agents able to run job")
}
dec := decision{
machineID: target.MState.ID,
}
return &dec, nil
}
// sortedAgents returns a list of AgentState objects sorted ascending
// by the number of scheduled units
func (lls *leastLoadedScheduler) sortedAgents(clust *clusterState) []*agent.AgentState {
agents := clust.agents()
sas := make(sortableAgentStates, 0)
for _, as := range agents {
sas = append(sas, as)
}
sort.Sort(sas)
return []*agent.AgentState(sas)
}
type sortableAgentStates []*agent.AgentState
func (sas sortableAgentStates) Len() int { return len(sas) }
func (sas sortableAgentStates) Swap(i, j int) { sas[i], sas[j] = sas[j], sas[i] }
func (sas sortableAgentStates) Less(i, j int) bool {
niUnits := len(sas[i].Units)
njUnits := len(sas[j].Units)
return niUnits < njUnits || (niUnits == njUnits && sas[i].MState.ID < sas[j].MState.ID)
}