org.apache.beam.fn.harness.debug

Class DataSampler

java.lang.Object

org.apache.beam.fn.harness.debug.DataSampler

public class DataSampler
extends java.lang.Object

The DataSampler is a global (per SDK Harness) object that facilitates taking and returning samples to the Runner Harness. The class is thread-safe with respect to executing ProcessBundleDescriptors. Meaning, different threads executing different PBDs can sample simultaneously, even if computing the same logical PCollection.

Constructor Summary

Constructors

Constructor and Description
DataSampler() Creates a DataSampler to sample every 1000 elements while keeping a maximum of 10 in memory.
DataSampler(int maxSamples, int sampleEveryN)

Method Summary

Modifier and Type	Method and Description
org.apache.beam.model.fnexecution.v1.BeamFnApi.InstructionResponse.Builder	handleDataSampleRequest(org.apache.beam.model.fnexecution.v1.BeamFnApi.InstructionRequest request) Returns all collected samples.
<T> OutputSampler<T>	sampleOutput(java.lang.String pcollectionId, org.apache.beam.sdk.coders.Coder<T> coder) Creates and returns a class to sample the given PCollection in the given ProcessBundleDescriptor.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DataSampler

public DataSampler()

Creates a DataSampler to sample every 1000 elements while keeping a maximum of 10 in memory.

DataSampler

public DataSampler(int maxSamples,
                   int sampleEveryN)

Parameters:

maxSamples - Sets the maximum number of samples held in memory at once.

sampleEveryN - Sets how often to sample.

Method Detail

sampleOutput

public <T> OutputSampler<T> sampleOutput(java.lang.String pcollectionId,
                                         org.apache.beam.sdk.coders.Coder<T> coder)

Creates and returns a class to sample the given PCollection in the given ProcessBundleDescriptor. Uses the given coder encode samples as bytes when responding to a SampleDataRequest.

Invoked by multiple bundle processing threads in parallel when a new bundle processor is being instantiated.

Type Parameters:

T - The type of element contained in the PCollection.

Parameters:

pcollectionId - The PCollection to take intermittent samples from.

coder - The coder associated with the PCollection. Coder may be from a nested context.

Returns:

the OutputSampler corresponding to the unique PBD and PCollection.

handleDataSampleRequest

public org.apache.beam.model.fnexecution.v1.BeamFnApi.InstructionResponse.Builder handleDataSampleRequest(org.apache.beam.model.fnexecution.v1.BeamFnApi.InstructionRequest request)

Returns all collected samples. Thread-safe.

Parameters:

request - The instruction request from the FnApi. Filters based on the given SampleDataRequest.

Returns:

Returns all collected samples.