版本：v1.2

Automatically scale workloads by resource utilization metrics and cron

Prerequisite

Make sure auto-scaler trait controller is installed in your cluster

Install auto-scaler trait controller with helm

Add helm chart repo for autoscaler trait

helm repo add oam.catalog  http://oam.dev/catalog/

Update the chart repo
```
helm repo update
```

Install autoscaler trait controller

helm install --create-namespace -n vela-system autoscalertrait oam.catalog/autoscalertrait

Autoscale depends on metrics server, please enable it in your Kubernetes cluster at the beginning.

Note: autoscale is one of the extension capabilities installed from cap center, please install it if you can't find it in vela traits.

Setting cron auto-scaling policy

Introduce how to automatically scale workloads by cron.

Prepare Appfile

name: testapp

services:
  express-server:
    # this image will be used in both build and deploy steps
    image: oamdev/testapp:v1

    cmd: ["node", "server.js"]
    port: 8080

    autoscale:
      min: 1
      max: 4
      cron:
        startAt:  "14:00"
        duration: "2h"
        days:     "Monday, Thursday"
        replicas: 2
        timezone: "America/Los_Angeles"

The full specification of autoscale could show up by $ vela show autoscale.

Deploy an application

$ vela up
  Parsing vela.yaml ...
  Loading templates ...
  
  Rendering configs for service (express-server)...
  Writing deploy config to (.vela/deploy.yaml)
  
  Applying deploy configs ...
  Checking if app has been deployed...
  App has not been deployed, creating a new deployment...
  ✅ App has been deployed 🚀🚀🚀
      Port forward: vela port-forward testapp
               SSH: vela exec testapp
           Logging: vela logs testapp
        App status: vela status testapp
    Service status: vela status testapp --svc express-server

Check the replicas and wait for the scaling to take effect

Check the replicas of the application, there is one replica.

$ vela status testapp
About:

  Name:         testapp
  Namespace:    default
  Created at:   2020-11-05 17:09:02.426632 +0800 CST
  Updated at:   2020-11-05 17:09:02.426632 +0800 CST

Services:

  - Name: express-server
    Type: webservice
    HEALTHY Ready: 1/1
    Traits:
      - ✅ autoscale: type: cron    replicas(min/max/current): 1/4/1
    Last Deployment:
      Created at: 2020-11-05 17:09:03 +0800 CST
      Updated at: 2020-11-05T17:09:02+08:00

Wait till the time clocks startAt, and check again. The replicas become to two, which is specified as replicas in vela.yaml.

$ vela status testapp
About:

  Name:         testapp
  Namespace:    default
  Created at:   2020-11-10 10:18:59.498079 +0800 CST
  Updated at:   2020-11-10 10:18:59.49808 +0800 CST

Services:

  - Name: express-server
    Type: webservice
    HEALTHY Ready: 2/2
    Traits:
      - ✅ autoscale: type: cron    replicas(min/max/current): 1/4/2
    Last Deployment:
      Created at: 2020-11-10 10:18:59 +0800 CST
      Updated at: 2020-11-10T10:18:59+08:00

Wait after the period ends, the replicas will be one eventually.

Setting auto-scaling policy of CPU resource utilization

Introduce how to automatically scale workloads by CPU resource utilization.

Prepare Appfile

Modify vela.yaml as below. We add field services.express-server.cpu and change the auto-scaling policy from cron to cpu utilization by updating filed services.express-server.autoscale.

name: testapp

services:
  express-server:
    image: oamdev/testapp:v1
      
    cmd: ["node", "server.js"]
    port: 8080
    cpu: "0.01"

    autoscale:
      min: 1
      max: 5
      cpuPercent: 10

Deploy an application
```
$ vela up
```

Expose the service entrypoint of the application

$ vela port-forward helloworld 80
Forwarding from 127.0.0.1:80 -> 80
Forwarding from [::1]:80 -> 80

Forward successfully! Opening browser ...
Handling connection for 80
Handling connection for 80
Handling connection for 80
Handling connection for 80

On your macOS, you might need to add sudo ahead of the command.

Monitor the replicas changing

Continue to monitor the replicas changing when the application becomes overloaded. You can use Apache HTTP server benchmarking tool ab to mock many requests to the application.

$ ab -n 10000 -c 200 http://127.0.0.1/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests

The replicas gradually increase from one to four.

$ vela status helloworld --svc frontend
About:

  Name:         helloworld
  Namespace:    default
  Created at:   2020-11-05 20:07:21.830118 +0800 CST
  Updated at:   2020-11-05 20:50:42.664725 +0800 CST

Services:

  - Name: frontend
    Type: webservice
    HEALTHY Ready: 1/1
    Traits:
      - ✅ autoscale: type: cpu     cpu-utilization(target/current): 5%/10%  replicas(min/max/current): 1/5/2
    Last Deployment:
      Created at: 2020-11-05 20:07:23 +0800 CST
      Updated at: 2020-11-05T20:50:42+08:00

$ vela status helloworld --svc frontend
About:

  Name:         helloworld
  Namespace:    default
  Created at:   2020-11-05 20:07:21.830118 +0800 CST
  Updated at:   2020-11-05 20:50:42.664725 +0800 CST

Services:

  - Name: frontend
    Type: webservice
    HEALTHY Ready: 1/1
    Traits:
      - ✅ autoscale: type: cpu     cpu-utilization(target/current): 5%/14%  replicas(min/max/current): 1/5/4
    Last Deployment:
      Created at: 2020-11-05 20:07:23 +0800 CST
      Updated at: 2020-11-05T20:50:42+08:00

Stop ab tool, and the replicas will decrease to one eventually.

Prerequisite​

Setting cron auto-scaling policy​

Setting auto-scaling policy of CPU resource utilization​

Prerequisite

Setting cron auto-scaling policy

Setting auto-scaling policy of CPU resource utilization