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Convox allows you to easily scale any Service on the following dimensions:
You can specify the scale for any Service in your convox.yml
services:
web:
scale:
count: 2
cpu: 250
memory: 512
If you specify a static
countit will only be used on first deploy. Subsequent changes must be made using theconvoxCLI.
$ convox scale
NAME DESIRED RUNNING CPU MEMORY
web 2 2 250 512
$ convox scale web --count=3
Scaling web...
2020-01-01T00:00:00Z system/k8s/web Scaled up replica set web-65f45567d to 2
2020-01-01T00:00:00Z system/k8s/web-65f45567d Created pod: web-65f45567d-c7sdw
2020-01-01T00:00:00Z system/k8s/web-65f45567d-c7sdw Successfully assigned dev-convox/web-65f45567d-c7sdw to node
2020-01-01T00:00:00Z system/k8s/web-65f45567d-c7sdw Container image "registry.dev.convox/convox:web.BABCDEFGHI" already present on machine
2020-01-01T00:00:00Z system/k8s/web-65f45567d-c7sdw Created container main
2020-01-01T00:00:00Z system/k8s/web-65f45567d-c7sdw Started container main
OK
Changes to
cpuormemoryshould be done in yourconvox.yml, and a new release of your app deployed.
To use autoscaling you must specify a range for allowable Process count and target values for CPU and Memory utilization (in percent):
service:
web:
scale:
count: 1-10
targets:
cpu: 70
memory: 90
The number of Processes will be continually adjusted to maintain your target metrics.
You must consider that the targets for CPU and Memory use the service replicas limits to calculate the utilization percentage. So if you set the target for CPU as 70 and have two replicas, it will trigger the auto-scale only if the utilization percentage sum divided by the replica’s count is bigger than 70%. The desired replicas will be calculated to satisfy the percentage. Being the currentMetricValue computed by taking the average of the given metric across all service replicas.
desiredReplicas = ceil[currentReplicas * ( currentMetricValue / desiredMetricValue )]
*To use Datadog metrics for autoscaling your rack must be updated to version 3.9.1 or later. You can find your rack’s version by running convox rack -r rackNAME. If you are on an older version, please update your rack to use this feature.
To autoscale based on Datadog metrics you must first have Datadog and the Datadog Cluster Agent installed. If you used the datadog-agent-all-features.yaml when configuring Datadog then you will already have the Datadog Cluster Agent installed.
You can check your cluster’s pods to see what is installed:
-n NAMESPACE_NAME option to the end of the command $ kubectl get pods
NAME READY STATUS RESTARTS AGE
datadog-bjw2m 5/5 Running 0 16m
datadog-cluster-agent-b5fd4b7f5-tmkql 1/1 Running 0 16m
datadog-j9c9t 5/5 Running 0 15m
datadog-pnrln 5/5 Running 0 16m
datadog-vdzc5 5/5 Running 0 16m
If your installation does not have an active datadog-cluster-agent pod you can install the Datadog Cluster Agent by following the instructions from the Datadog Documentation.
Once the Datadog Cluster Agent is setup follow this Datadog Documentation to configure your Datadog Cluster Agent with an external metrics provider service.
Next to setup DatadogMetric follow these steps from the Datadog Documentation.
You can now create scaling manifests based on Datadog’s provided template:
apiVersion: datadoghq.com/v1alpha1
kind: DatadogMetric
metadata:
name: <your_datadogmetric_name>
spec:
query: <your_custom_query>
You can deploy these metrics with kubectl apply -f your-custom-metric-file.yaml
You will finally then need to deploy a service for your apps to push metrics to Datadog. You can use this example or write your own based on your own custom configurations:
$ cat dd-agent-service.yaml
apiVersion: v1
kind: Service
metadata:
name: dd-agent
spec:
selector:
app: datadog
ports:
- protocol: UDP
port: 8125
targetPort: 8125
Deploy the service with kubectl apply -f dd-agent-service.yaml
In this example we will start with a nodejs app that has been configured to scale with Datadog to demonstrate how to setup scaling with this method.
Based on the provided template we can make a basic page views metric for the node application:
$ cat page-views-metrics.yaml
apiVersion: datadoghq.com/v1alpha1
kind: DatadogMetric
metadata:
name: page-views-metrics
spec:
query: avg:page.views{*}.as_count()
Then add the metric to your cluster via kubectl apply -f page-views-metrics.yaml
Now we are going to look at the configuration of the convox.yaml from our nodejs app to autoscale based on this newly created metric.
We will specify the datadogmetric object name in the scale.targets[].external section. The datadogmetric object name convention to use in scale.targets[].external section is : datadogmetric@<namespace>:<datadogmetric_name>
We set the env var DD_AGENT_HOST to point at the dd-agent service we previously made to push information to Datadog.
environment:
- PORT=3000
services:
web:
build: .
port: 3000
environment:
- DD_AGENT_HOST=dd-agent.default.svc.cluster.local
scale:
count: 1-3
targets:
external:
- name: "datadogmetric@default:page-views-metrics"
averageValue: 5
You can now deploy the application with convox apps create -a nodejs then convox deploy -a nodejs
Once deployed you can check the replica count and deployed services:
$ convox ps -a nodejs
ID SERVICE STATUS RELEASE STARTED COMMAND
web-5bc58fb455-psd9h web running RMOGLKGFMOW 7 minutes ago
$ convox services -a nodejs
SERVICE DOMAIN PORTS
web web.nodejs.1e5717e816e99649.convox.cloud 443:3000
You can simulate some views to make the application scale via:
$ while true; do curl https://<YOUR_SERVICE_DOMAIN>/; sleep 0.2; done
You can then see that the application is beginning to scale up:
$ convox ps -a nodejs
ID SERVICE STATUS RELEASE STARTED COMMAND
web-5675cccf75-chmcc web running RAZUSIKBQGX 25 seconds ago
web-5675cccf75-dm6kb web running RAZUSIKBQGX 6 minutes ago
When you end the view simulation it will scale down again:
$ convox ps -a nodejs
ID SERVICE STATUS RELEASE STARTED COMMAND
web-5675cccf75-dm6kb web running RAZUSIKBQGX 11 minutes ago
