Scaling Instances

You can scale CDAP components (instances of services and workers) using:

the Scaling methods of the Lifecycle Microservices;
the Get/Set Commands of the Command Line Interface; or
the ProgramClient API of the Java Client API.

The examples given below use the Lifecycle Microservices.

Scaling Services

You can query or change the number of instances of a service by using the instances parameter with HTTP GET or PUT methods:

GET /v3/namespaces/<namespace-id>/apps/<app-id>/services/<service-id>/instances
PUT /v3/namespaces/<namespace-id>/apps/<app-id>/services/<service-id>/instances

with the arguments as a JSON string in the body:

{ "instances" : <quantity> }

Parameter	Description
`namespace-id`	Namespace ID
`app-id`	Name of the application
`service-id`	Name of the service
`quantity`	Number of instances to be used

Note: You can scale system services using the Monitor Microservices Scaling System Services.

Examples

Retrieve the number of instances of the service CatalogLookup in the application PurchaseHistory in the namespace default:
```
GET /v3/namespaces/default/apps/PurchaseHistory/services/CatalogLookup/instances
```
Set the number of handler instances of the service RetrieveCounts of the application WordCount:
```
PUT /v3/namespaces/default/apps/WordCount/services/RetrieveCounts/instances
```
with the arguments as a JSON string in the body:
```
{ "instances" : 2 }
```
Using curl and the CDAP Sandbox:

Linux

$ curl -w"\n" -X PUT "http://localhost:11015/v3/namespaces/default/apps/WordCount/services/RetrieveCounts/instances" \ -d '{ "instances" : 2 }'

Windows

> curl -X PUT "http://localhost:11015/v3/namespaces/default/apps/WordCount/services/RetrieveCounts/instances" ^ -d "{ \"instances\" : 2 }"

Scaling Workers

You can query or change the number of instances of a worker by using the instances parameter with HTTP GET or PUT methods:

GET /v3/namespaces/<namespace-id>/apps/<app-id>/workers/<worker-id>/instances
PUT /v3/namespaces/<namespace-id>/apps/<app-id>/workers/<worker-id>/instances

with the arguments as a JSON string in the body:

{ "instances" : <quantity> }

Parameter	Description
`namespace-id`	Namespace ID
`app-id`	Name of the application
`worker-id`	Name of the worker
`quantity`	Number of instances to be used

Example

Retrieve the number of instances of the worker DataWorker in the application DemoApp in the namespace default:

GET /v3/namespaces/default/apps/DemoApp/workers/DataWorker/instances