This guide covers how you can quickly get started using Agones to create a Fleet Autoscaler to manage your fleet size automatically, based on actual load.
It is assumed that you have followed the instructions to Create a Game Server Fleet and you have a running fleet of game servers.
- Create a Fleet Autoscaler in Kubernetes using Agones custom resource.
- Watch the Fleet scale up when allocating GameServers
- Watch the Fleet scale down when shutting down allocated GameServers
- Edit the autoscaler specification to apply live changes
Let's create a Fleet Autoscaler using the following command :
kubectl apply -f https://raw.githubusercontent.com/GoogleCloudPlatform/agones/master/examples/simple-udp/fleetautoscaler.yaml
You should see a successful ouput similar to this :
fleetautoscaler.stable.agones.sev "simple-udp-autoscaler" created
This has created a FleetAutoscaler record inside Kubernetes.
kubectl describe fleetautoscaler simple-udp-autoscaler
It should look something like this:
Name: simple-udp-autoscaler
Namespace: default
Labels: <none>
Annotations: kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"st
able.agones.dev/v1alpha1","kind":"FleetAutoscaler","metadata":{"annotations":{},
"name":"simple-udp-autoscaler","namespace":"default"},...
API Version: stable.agones.dev/v1alpha1
Kind: FleetAutoscaler
Metadata:
Cluster Name:
Creation Timestamp: 2018-10-02T15:19:58Z
Generation: 1
Owner References:
API Version: stable.agones.dev/v1alpha1
Block Owner Deletion: true
Controller: true
Kind: Fleet
Name: simple-udp
UID: 9960762e-c656-11e8-933e-fa163e07a1d4
Resource Version: 6123197
Self Link: /apis/stable.agones.dev/v1alpha1/namespaces/default/f
leetautoscalers/simple-udp-autoscaler
UID: 9fd0efa1-c656-11e8-933e-fa163e07a1d4
Spec:
Fleet Name: simple-udp
Policy:
Buffer:
Buffer Size: 2
Max Replicas: 10
Min Replicas: 2
Type: Buffer
Status:
Able To Scale: true
Current Replicas: 2
Desired Replicas: 2
Last Scale Time: <nil>
Scaling Limited: false
Events: <none>
You can see the status (able to scale, not limited), the last time the fleet was scaled (nil for never) and the current and desired fleet size.
The autoscaler works by changing the desired size, and the fleet creates/deletes game server instances to achieve to that number. The convergence is achieved in time, which is usually measured in seconds.
If you're interested in more details for game server allocation, you should consult the Create a Game Server Fleet page. In here we are only interested in triggering allocations to see the autoscaler in action.
kubectl create -f https://raw.githubusercontent.com/GoogleCloudPlatform/agones/master/examples/simple-udp/fleetallocation.yaml -o yaml
You should get in return the allocated game server details, which should end with something like:
status:
address: 10.30.64.99
nodeName: universal3
ports:
- name: default
port: 7131
state: Allocated
Note the address and port, you might need them later to connect to the server.
Now let's wait a few seconds to allow the autoscaler to detect the change in the fleet and check again its status
kubectl describe fleetautoscaler simple-udp-autoscaler
The last part should look something like this:
Spec:
Fleet Name: simple-udp
Policy:
Buffer:
Buffer Size: 2
Max Replicas: 10
Min Replicas: 2
Type: Buffer
Status:
Able To Scale: true
Current Replicas: 3
Desired Replicas: 3
Last Scale Time: 2018-10-02T16:00:02Z
Scaling Limited: false
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal AutoScalingFleet 2m fleetautoscaler-controller Scaling fleet simple-udp from 2 to 3
You can see that the fleet size has increased, the autoscaler having compensated for the allocated instance. Last Scale Time has been updated, and a scaling event has been logged.
Double-check the actual number of game server instances and status by running
kubectl get gs -o=custom-columns=NAME:.metadata.name,STATUS:.status.state,IP:.status.address,PORT:.status.ports
This will get you a list of all the current GameSevers and their Status > State.
NAME STATUS IP PORT
simple-udp-mzhrl-hz8wk Allocated 10.30.64.99 [map[name:default port:7131]]
simple-udp-mzhrl-k6jg5 Ready 10.30.64.100 [map[name:default port:7243]]
simple-udp-mzhrl-n2sk2 Ready 10.30.64.168 [map[name:default port:7658]]
Since we've only got one allocation, we'll just grab the details of the IP and port of the
only allocated GameServer:
kubectl get $(kubectl get fleetallocation -o name) -o jsonpath='{.status.GameServer.status.GameServer.status.ports[0].port}'
This should output your Game Server IP address and port. (eg 10.130.65.208:7936)
You can now communicate with the GameServer:
nc -u {IP} {PORT}
Hello World !
ACK: Hello World !
EXIT
You can finally type EXIT which tells the SDK to run the Shutdown command, and therefore shuts down the GameServer.
Now let's wait a few seconds to allow the autoscaler to detect the change in the fleet and check again its status
kubectl describe fleetautoscaler simple-udp-autoscaler
It should look something like this:
Spec:
Fleet Name: simple-udp
Policy:
Buffer:
Buffer Size: 2
Max Replicas: 10
Min Replicas: 2
Type: Buffer
Status:
Able To Scale: true
Current Replicas: 3
Desired Replicas: 2
Last Scale Time: 2018-10-02T16:09:02Z
Scaling Limited: false
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal AutoScalingFleet 9m fleetautoscaler-controller Scaling fleet simple-udp from 2 to 3
Normal AutoScalingFleet 45s fleetautoscaler-controller Scaling fleet simple-udp from 3 to 2
You can see that the fleet size has decreased, the autoscaler adjusting to game server instance being de-allocated, the Last Scale Time and the events have been updated. Note that simple-udp game server instance you just closed earlier might stay a bit in 'Unhealthy' state (and its pod in 'Terminating' until it gets removed.
Double-check the actual number of game server instances and status by running
kubectl get gs -o=custom-columns=NAME:.metadata.name,STATUS:.status.state,IP:.status.address,PORT:.status.ports
This will get you a list of all the current GameSevers and their Status > State.
NAME STATUS IP PORT
simple-udp-mzhrl-k6jg5 Ready 10.30.64.100 [map[name:default port:7243]]
simple-udp-mzhrl-t7944 Ready 10.30.64.168 [map[port:7561 name:default]]
We can also change the configuration of the FleetAutoscaler of the running Fleet, and have the changes
applied live, without interruptions of service.
Run kubectl edit fleetautoscaler simple-udp-autoscaler and set the bufferSize field to 5.
Let's look at the list of game servers again. Run watch kubectl get gs -o=custom-columns=NAME:.metadata.name,STATUS:.status.state,IP:.status.address,PORT:.status.ports
until you can see that are 5 ready server instances:
NAME STATUS IP PORT
simple-udp-mzhrl-7jpkp Ready 10.30.64.100 [map[name:default port:7019]]
simple-udp-mzhrl-czt8v Ready 10.30.64.168 [map[name:default port:7556]]
simple-udp-mzhrl-k6jg5 Ready 10.30.64.100 [map[name:default port:7243]]
simple-udp-mzhrl-nb8h2 Ready 10.30.64.168 [map[name:default port:7357]]
simple-udp-mzhrl-qspb6 Ready 10.30.64.99 [map[name:default port:7859]]
simple-udp-mzhrl-zg9rq Ready 10.30.64.99 [map[name:default port:7745]]
Read the advanced Scheduling and Autoscaling guide, for more details on autoscaling.
If you want to use your own GameServer container make sure you have properly integrated the Agones SDK.