⚡ $ cdk8s import https://github.com/kedacore/keda/releases/download/v2.8.0/keda-2.8.0.yaml --output src/imports/  ------------------------------------------------------------------------------------------------  A new version 2.0.88 of cdk8s-cli is available (current 2.0.13).  Run "npm install -g cdk8s-cli" to install the latest version on your system.  For additional installation methods, see https://cdk8s.io/docs/latest/getting-started  ------------------------------------------------------------------------------------------------  Importing resources, this may take a few moments...  keda.sh    keda.sh/clustertriggerauthentication    keda.sh/scaledjob    keda.sh/scaledobject    keda.sh/triggerauthentication

## 🚀 **Write code** <a name="Write-code"></a>- Overview of keda scaledObjects in this post  <img src=https://raw.githubusercontent.com/vumdao/keda-hands-on/master/docs/images/flow.png width=900>- It's much more convinient to use visual code writing KEDA scaledobject in typescript language. We can read the document and find all references of construct, objects and properties of KEDA CRDs- This blog provides the usecase of creating scaledObject (SO) for Apache airflow worker component. It contains 3 triggers (Scalers) in the SO### 1. [Cron](https://keda.sh/docs/2.8/scalers/cron/) - Scale applications based on a cron schedule.- Airflow server scheduled pipelines and worker components are scaled out at that time, but it takes time to start nodes, join node to cluster and Pod ready (about 2-3mins) so we use cron to pre-scale workers### 2. [PostgreSQL](https://keda.sh/docs/2.8/scalers/postgresql/) - Scale applications based on a PostgreSQL query.  - This scaler bases on the output of query command to scaleout works, here we count the number of running/queued airflow task instances belongs to scheduled pipeline (eg. running reports). Divide the count number to Airflow worker concurrency (eg. 16 as default)  - `targetQueryValue: '1.5'` - The result of above calculation divide to this target value to decide how many pods will be scaled out### 3. [CPU](https://keda.sh/docs/2.8/scalers/cpu/) - Scale applications based on cpu metrics  - This is optional as it ensure provisioning workers when CPU Utilization is higher than 80%- PostgreSQL Scaler requires `TriggerAuthentication` to provide password of airflow user in order to query the database. The credential is get from K8S secret `airflow-secret` within the `airflow` namespace

const pgAuth = new TriggerAuthentication(this, 'KedaPostgresAuthentication', {  metadata: {    name: 'keda-airflow-postgresql-auth',    namespace: 'airflow',  },  spec: {    secretTargetRef: [{      parameter: 'password',      name: 'airflow-secret',      key: 'postgresql-password',    }],  },});

- Some SO specs need to know  - `pollingInterval`: This is the interval to check each trigger on. By default KEDA will check each trigger source on every ScaledObject every 30 seconds. So to reduce the query connections/workload to airflow database we need to care this vaule.  - `cooldownPeriod`: The period to wait after the last trigger reported active before scaling the resource back to 0.## 🚀 **Build keda scaledobjects from code** <a name="Build-keda-scaledobjects-from-code"></a>- Source code:

- Build resource

- Manifest yaml file

## 🚀 **Apply and test** <a name="Apply-and-test">- Apply manifest and check result

## 🚀 Conclusion <a name="Conclusion"></a>- Within the Scaledobject class, you can jump to definition to understand the meaning of each properties and also know which required/optional attributes.- We can create a custom construct and base on that to provision multiple KEDA scaledobjects with customize specs/meta such as min/max/desired replicas, triggers, trigger authentication, etc.---
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