org.apache.samza.application.descriptors

Interface ApplicationDescriptor<S extends ApplicationDescriptor>

All Known Subinterfaces:

StreamApplicationDescriptor, TaskApplicationDescriptor

@InterfaceStability.Evolving
public interface ApplicationDescriptor<S extends ApplicationDescriptor>

An ApplicationDescriptor contains the description of inputs, outputs, state, configuration and the processing logic for a SamzaApplication.

This is the base ApplicationDescriptor and provides functionality common to all SamzaApplication. SamzaApplication.describe(S) will provide access to a StreamApplicationDescriptor with additional functionality for describing High Level API applications. Similarly, SamzaApplication.describe(S) will provide access to a TaskApplicationDescriptor with additional functionality for describing Low Level API applications.

Use the ApplicationDescriptor to set the container scope context factory using withApplicationContainerContextFactory(org.apache.samza.context.ApplicationContainerContextFactory<?>), and task scope context factory using withApplicationTaskContextFactory(org.apache.samza.context.ApplicationTaskContextFactory<?>). Please note that the terms container and task here refer to the units of physical and logical parallelism, not the programming API.

Method Summary

Modifier and Type	Method and Description
Config	getConfig() Get the configuration for the application.
S	withApplicationContainerContextFactory(ApplicationContainerContextFactory<?> factory) Sets the ApplicationContainerContextFactory for this application.
S	withApplicationTaskContextFactory(ApplicationTaskContextFactory<?> factory) Sets the ApplicationTaskContextFactory for this application.
S	withDefaultSystem(SystemDescriptor<?> defaultSystemDescriptor) Sets the SystemDescriptor for the default system for the application.
S	withMetricsReporterFactories(java.util.Map<java.lang.String,MetricsReporterFactory> reporterFactories) Sets the MetricsReporterFactorys for creating the MetricsReporters to use for the application.
S	withProcessorLifecycleListenerFactory(ProcessorLifecycleListenerFactory listenerFactory) Sets the ProcessorLifecycleListenerFactory for this application.

Method Detail

getConfig

Config getConfig()

Get the configuration for the application.

Returns:

config for the application

withDefaultSystem

S withDefaultSystem(SystemDescriptor<?> defaultSystemDescriptor)

Sets the SystemDescriptor for the default system for the application.

The default system is used by the framework for creating any internal (e.g., coordinator, changelog, checkpoint) streams. In an StreamApplication, it is also used for creating any intermediate streams; e.g., those created by the MessageStream.partitionBy(org.apache.samza.operators.functions.MapFunction<? super M, ? extends K>, org.apache.samza.operators.functions.MapFunction<? super M, ? extends V>, org.apache.samza.serializers.KVSerde<K, V>, java.lang.String) and MessageStream.broadcast(org.apache.samza.serializers.Serde<M>, java.lang.String) operators.

If the default system descriptor is set, it must be set before creating any input/output/intermediate streams.

Parameters:

defaultSystemDescriptor - the SystemDescriptor for the default system for the application

Returns:

this ApplicationDescriptor

withApplicationContainerContextFactory

S withApplicationContainerContextFactory(ApplicationContainerContextFactory<?> factory)

Sets the ApplicationContainerContextFactory for this application. This will be used to create one instance of an ApplicationContainerContext for each container. All tasks in the same container will share the same ApplicationContainerContext instance. The ApplicationContainerContext can be accessed through the Context.

Setting this is optional.

The provided factory instance must be Serializable.

Parameters:

factory - the ApplicationContainerContextFactory for this application

Returns:

this ApplicationDescriptor

withApplicationTaskContextFactory

S withApplicationTaskContextFactory(ApplicationTaskContextFactory<?> factory)

Sets the ApplicationTaskContextFactory for this application. Each task will be given access to a different instance of the ApplicationTaskContext that this creates. The ApplicationTaskContext can be accessed through the Context.

Setting this is optional.

The provided factory instance must be Serializable.

Parameters:

factory - the ApplicationTaskContextFactory for this application

Returns:

this ApplicationDescriptor

withProcessorLifecycleListenerFactory

S withProcessorLifecycleListenerFactory(ProcessorLifecycleListenerFactory listenerFactory)

Sets the ProcessorLifecycleListenerFactory for this application.

Setting a ProcessorLifecycleListenerFactory is optional to a user application. It allows users to plug in optional code to be invoked in different stages before/after the main processing logic is started/stopped in the application.

The provided factory instance must be Serializable.

Parameters:

listenerFactory - the user implemented ProcessorLifecycleListenerFactory that creates lifecycle listener with callback methods before and after the start/stop of each StreamProcessor in the application

Returns:

this ApplicationDescriptor

withMetricsReporterFactories

S withMetricsReporterFactories(java.util.Map<java.lang.String,MetricsReporterFactory> reporterFactories)

Sets the MetricsReporterFactorys for creating the MetricsReporters to use for the application.

The provided MetricsReporterFactory instances must be Serializable.

Parameters:

reporterFactories - a map of MetricsReporter names to their factories.

Returns:

this ApplicationDescriptor