Scaling Instances

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

• the Scaling methods of the Lifecycle HTTP RESTful API;
• 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 HTTP RESTful API.

Scaling Flowlets

You can query and set the number of instances executing a given flowlet by using the instances parameter with HTTP GET and PUT methods:

GET /v3/namespaces/<namespace-id>/apps/<app-id>/flows/<flow-id>/flowlets/<flowlet-id>/instances
PUT /v3/namespaces/<namespace-id>/apps/<app-id>/flows/<flow-id>/flowlets/<flowlet-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 being called
flow-id	Name of the flow
flowlet-id	Name of the flowlet
quantity	Number of instances to be used

Examples

• Retrieve the number of instances of the flowlet saver in the flow WhoFlow of the application HelloWorld in the namespace default:

  GET /v3/namespaces/default/apps/HelloWorld/flows/WhoFlow/flowlets/saver/instances
  

• Set the number of instances of the flowlet saver in the flow WhoFlow of the application HelloWorld in the namespace default:

  PUT /v3/namespaces/default/apps/HelloWorld/flows/WhoFlow/flowlets/saver/instances
  

  with the arguments as a JSON string in the body:

  { "instances" : 2 }
  

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 HTTP RESTful API 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 Standalone CDAP:

  • Linux
  • Windows

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

  > 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 HelloWorld in the namespace default:

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