GamerServer scaling down priority

Background

Generally speaking, the number of players on each game server will be different. When we scaling down, we can select a replica with fewer users and delete it. In this way, the scaling-down overhead on the application side can be smaller, and at the same time, the utilization efficiency of the underlying resources can be improved.

We can set a certain priority for each game server based on some application metrics. When scaling down, we choose the replica with the lower priority to delete.

Implementation

Add carrier.ocgi.dev/gs-deletion-cost(int64) annotation to GameServer. The annotation can be added by user calling SDK or added by our component cost-server.

The cost-server obtains data from the metric server according to the carrier.ocgi.dev/gs-cost-metrics-name annotation specified in the squad, and adds carrier.ocgi.dev/gs-deletion-cost annotation to the gs.
If the GameServer does not set carrier.ocgi.dev/gs-deletion-cost, it is calculated according to Int64 Max.
If all GameServers are not set, enter the original logic, and select the node with fewer GameServers on the node for shrinking, or shrinking according to the oldest creation time.

The Carrier controller is sorted in ascending order of the value, and the top N is reduced.

Cost-server Introduction

cost-server watch the create and update event of Squad;
The cost-server obtains the corresponding metric name from the annotation named carrier.ocgi.dev/gs-cost-metrics-name;
If the metric is cpu or memory, the cost-server will obtain data from the metric server; if it is other metrics, it will obtain data from the custom metric server;
The final data will be written to the annotation of GameServer, for example: carrier.ocgi. dev/gs-deletion-cost: "2101248000";

Usage

If you are using metrics such as cpu and memory, only need to specify carrier.ocgi.dev/gs-cost-metrics-name on Squad;
If you want to use custom metrics, such as the number of connections, the user can use one of the following two methods:

Add carrier.ocgi.dev/gs-cost-metrics-name: <number of connections> to Squad, there is a certain delay in this method
With the SDK SetAnnotation method, set carrier.ocgi.dev/gs-deletion-cost for each GameServer

Examples

Set cost for GameServer based on the cost-server.

Create a Squad

# cat <<EOF | kubectl apply -f -
apiVersion: carrier.ocgi.dev/v1alpha1
kind: Squad
metadata:
  annotations:
    carrier.ocgi.dev/gs-cost-metrics-name: memory
    network.cni/networkname: tke-direct-eni
  name: squad2
spec:
  replicas: 4
  scheduling: MostAllocated
  selector:
    matchLabels:
      carrier.ocgi.dev/squad: squad2
  template:
    metadata:
      annotations:
        network.cni/networkname: tke-direct-eni
      labels:
        foo: bar
    spec:
      ports:
        - container: simple-tcp
          containerPort: 7654
          name: default
          protocol: TCP
      template:
        spec:
          containers:
            - image: ocgi/simple-tcp:0.1
              name: server
          serviceAccountName: carrier-sdk

Fetch GameServers

# kubectl get gs -o wide
NAME                      STATE     ADDRESS         PORT   EXTERNALIP   PORTRANGE     NODE            AGE
squad2-56fbd4d75d-4js2f   Running   192.168.113.169                                   192.168.0.115   64m
squad2-56fbd4d75d-cqxtz   Running   192.168.113.165                                   192.168.0.115   64m
squad2-56fbd4d75d-gsh76   Running   192.168.113.166                                   192.168.0.129   64m
squad2-56fbd4d75d-mmcgf   Running   192.168.113.168                                   192.168.0.213   64m

Check the Cost

# kubectl get gs -o custom-columns="Name":".metadata.name","Cost":".metadata.annotations.carrier\.ocgi\.dev/gs-deletion-cost","UpdateTime":".metadata.annotations.carrier\.ocgi\.dev/deletion-cost-update-time"
Name                      Cost         UpdateTime
squad2-56fbd4d75d-4js2f   2101248000   2021-04-15 08:20:58 +0000 UTC
squad2-56fbd4d75d-cqxtz   2191360000   2021-04-15 08:20:58 +0000 UTC
squad2-56fbd4d75d-gsh76   2007040000   2021-04-15 08:20:58 +0000 UTC
squad2-56fbd4d75d-mmcgf   2068480000   2021-04-15 08:20:58 +0000 UTC

Scale-down the Squad

kubectl scale sqd squad2 --replicas=3

Check the Cost

# kubectl get gs -o custom-columns="Name":".metadata.name","Cost":".metadata.annotations.carrier\.ocgi\.dev/gs-deletion-cost","UpdateTime":".metadata.annotations.carrier\.ocgi\.dev/deletion-cost-update-time"
Name                      Cost         UpdateTime
squad2-56fbd4d75d-4js2f   2101248000   2021-04-15 08:21:43 +0000 UTC
squad2-56fbd4d75d-cqxtz   2191360000   2021-04-15 08:21:43 +0000 UTC
squad2-56fbd4d75d-mmcgf   2068480000   2021-04-15 08:21:43 +0000 UTC

As we can see, controller deleted the replica with the minimal Cost.