使用 Kubernetes 扩展专用游戏服务器：第4部分-缩减节点

apiVersion: v1
kind: Pod
metadata:
  generateName: "game-"
spec:
  hostNetwork: true
  restartPolicy: Never
  nodeSelector:
    role: game-server
  containers:
    - name: soccer-server
      image: gcr.io/soccer/soccer-server:0.1
      env:
        - name: SESSION_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        resources:
          limits:
            cpu: "0.1"
  affinity:
    podAffinity: # group game server Pods
      preferredDuringSchedulingIgnoredDuringExecution:
      - podAffinityTerm:
          labelSelector:
            matchLabels:
              sessions: game
          topologyKey: kubernetes.io/hostname

// scale scales nodes up and down, depending on CPU constraints
// this includes adding nodes, cordoning them as well as deleting them
func (s Server) scaleNodes() error {
        nl, err := s.newNodeList()
        if err != nil {
                return err
        }
        available := nl.cpuRequestsAvailable()
        if available < s.bufferCount {
                finished, err := s.uncordonNodes(nl, s.bufferCount-available)
                // short circuit if uncordoning means we have enough buffer now
                if err != nil || finished {
                        return err
                }
                nl, err := s.newNodeList()
                if err != nil {
                        return err
                }
                // recalculate
                available = nl.cpuRequestsAvailable()
                err = s.increaseNodes(nl, s.bufferCount-available)
                if err != nil {
                        return err
                }
        } else if s.bufferCount < available {
                err := s.cordonNodes(nl, available-s.bufferCount)
                if err != nil {
                        return err
                }
        }
        return s.deleteCordonedNodes()
}

// cordonNodes decrease the number of available nodes by the given number of cpu blocks (but not over),
// but cordoning those nodes that have the least number of games currently on them
func (s Server) cordonNodes(nl *nodeList, gameNumber int64) error {
       // … removed some input validation ... 
        // how many nodes (n) do we have to delete such that we are cordoning no more
        // than the gameNumber
        capacity := nl.nodes.Items[0].Status.Capacity[v1.ResourceCPU] //assuming all nodes are the same
        cpuRequest := gameNumber * s.cpuRequest
        diff := int64(math.Floor(float64(cpuRequest) / float64(capacity.MilliValue())))
        if diff <= 0 {
                log.Print("[Info][CordonNodes] No nodes to be cordoned.")
                return nil
        }
        log.Printf("[Info][CordonNodes] Cordoning %v nodes", diff)
        // sort the nodes, such that the one with the least number of games are first
        nodes := nl.nodes.Items
        sort.Slice(nodes, func(i, j int) bool {
                return len(nl.nodePods(nodes[i]).Items) < len(nl.nodePods(nodes[j]).Items)
        })
        // grab the first n number of them
        cNodes := nodes[0:diff]
        // cordon them all
        for _, n := range cNodes {
                log.Printf("[Info][CordonNodes] Cordoning node: %v", n.Name)
                err := s.cordon(&n, true)
                if err != nil {
                        return err
                }
        }
        return nil
}

// deleteCordonedNodes will delete a cordoned node if it
// the time since it was cordoned has expired
func (s Server) deleteCordonedNodes() error {
  nl, err := s.newNodeList()
  if err != nil {
     return err
  }
  l := int64(len(nl.nodes.Items))
  if l <= s.minNodeNumber {
     log.Print("[Info][deleteCordonedNodes] Already at minimum node count. exiting")
     return nil
  }
  var dn []v1.Node
  for _, n := range nl.cordonedNodes() {
     ct, err := cordonTimestamp(n)
     if err != nil {
        return err
     }
     pl := nl.nodePods(n)
     // if no game session pods && if they have passed expiry, then delete them
     if len(filterGameSessionPods(pl.Items)) == 0 && ct.Add(s.shutdown).Before(s.clock.Now()) {
        err := s.cs.CoreV1().Nodes().Delete(n.Name, nil)
        if err != nil {
           return errors.Wrapf(err, "Error deleting cordoned node: %v", n.Name)
        }
        dn = append(dn, n)
        // don't delete more nodes than the minimum number set
        if l--; l <= s.minNodeNumber {
           break
        }
     }
  }
  return s.nodePool.DeleteNodes(dn)
}