Page Comparison

Public interface to emit the preview data:

Code Block

language	java

public interface PreviewEmitter<V> PreviewEmitter {
	
	/**
 	 * Emitput the Map of properties corresponding to the given key.
 	 * @param key the key under which properties are stored
	 * @param propertyValues the map of property values to be stored under the given key
 	 */
	 void emitput(String key, Map<String, List<V>>List<Object>> propertyValues);
 
	/**
 	 * Emit the property specified by name and value for the given key.
 	 * @param key the key under which properties are stored
     * @param propertyName the the name of the property
	 * @param propertyValue the value associated with the property
 	 */
	 void emit(String key, String propertyName, VObject propertyValue);
	
}

2. Preview Context API

3. How the application will get access to the PreviewEmitter? Similar to Metric and @UseDataSet, instance of the PreviewEmitter will be injected by CDAP in the application.

Code Block

language	java

public class MyMapReduce extends AbstractMapReduce {
	private PreviewEmitter<String> emitter;
 
    @Override
    public void initialize() throws Exception {
		emitter.emit("MyMapReduce.initialize", "logical.start.time", getContext().getLogicalStartTime().toString());
		emitter.emit("MyMapReduce.initialize", "actual.start.time", System.currentTimeMillis().toString());
    }
 
    public MyMapper extends Mapper<byte[], Text, Text, Text> {
		@Override
		public void map(byte[] key, Text value, Context context) throws IOException {
			if (value.toString().startsWith("Product") {
				emitter.emit("MapReduce.map", "map.product", value.toString());	
			}
		}
	}
}

Preview Context Public API

Code Block

public interface PreviewContext() {
	/**
	 * boolean flag to indicate if preview is enabled or not.
	 */
	boolean isPreviewEnabled();
 
	/**
	 * get PreviewEmitter, PreviewEmitter can be used to emit objects collected by key and field names.
	 */
    PreviewEmitter getPreviewEmitter();
}

PreviewContext implementation will use previewId to create a preview emitter which can be obtained using getPreviewEmitter by programs. Programs can use isPreviewEnabled to check if preview is enabled before emitting.

How will CDAP get data from the preview?

Code Block

/**
 * Represents the state of the preview.
 */
public class PreviewStatePreviewStatus {
  public enum Status {
	RUNNING,
	COMPLETED,
	DEPLOY_FAILED,
	RUNTIME_FAILED	
  };
 
  Status previewStatus;
  @Nullable	
  String failureMessage;			
}
 
// This is internal interface which will be used by REST handlers
// to retrieve the preview information.
public interface PreviewInfoPreviewManager {
 
    /**
	 * Get the state of the preview represented by previewId.
     */
	PreviewStatePreviewStatus getStatus(PreviewId previewId);
 
	/**
	 * Get the data associated with the preview represented by previewId.
	 */
    Map<String, Map<String, List<V>>List<Object>> getData(PreviewId previewId);
 
	/**
	 * Get all metrics associated with the preview represented by previewId.
	 */
	Collection<MetricTimeSeries> getMetrics(PreviewId previewId);
  
 	/**
	 * Get all logs associated with the preview represented by previewId.
	 */
	StringList<LogEntry> getLogs(PreviewId previewId);
}
 
class PreviewId extends EntityId implements NamespaceId, ParentId<NamespaceId> {
	NamespaceId namespace;
    String preview;
}

...

Service	Standalone (Yes/No)	Preview (Yes/No)
userInterfaceService	Yes	No
trackerAppCreationService	Yes	No
router	Yes	No
streamService	YesYes	No
exploreExecutorService	Yes	No
exploreClient	Yes	No
metadataService	Yes	No
serviceStore (set/get service instances)	Yes	No
appFabricServer	Yes	No
previewServer	No	Yes
datasetService	Yes	Yes
metricsQueryService	Yes	No (Can call MetricStore query)
txService	YesYes	No (can use standalone's tx service)
externalAuthenticationServer (if security enabled)	Yes	Yes
logAppenderInitializer	Yes	Yes
kafkaClient(if audit enabled)	Yes	No
zkClient (if audit enabled)	Yes	No
authorizerInstantiator (started by default)	Yes	Yes?

AppFabricServer vs PreviewServer :

...

Services	AppFabricServer	PreviewServer
notificationService	Yes	No
schedulerService	Yes	No
applicationLifecycleService	Yes	Yes
systemArtifactLoader	Yes	Yes
programRuntimeService	Yes	Yes
streamCoordinatorClient	Yes	Yes
programLifecycleService	Yes	Yes
pluginService	Yes	Yes
httpServicehandlerHttpService	Yes	Yes (but only with preview handler). CDAP Router should route calls for preview here.

PreviewDatasetFramework

...

Versions Compared

Old Version 12

New Version 13

Key

PreviewDatasetFramework