Status
Current state: "Under Discussion"
Discussion thread: here (<- link to https://mail-archives.apache.org/mod_mbox/flink-dev/)
JIRA:
Released: TBD
Motivation
FLIP-27 sources are non-trivial to implement. At the same time, it is frequently required to generate arbitrary events with a "mock" source. Such requirement arises both for Flink users, in the scope of demo/PoC projects, and for Flink developers when writing tests. The go-to solution for these purposes so far was using pre-FLIP-27 APIs and implementing data generators as SourceFunctions
.
While the new FLIP-27 Source
interface introduces important additional functionality, it comes with significant complexity that presents a hurdle for Flink users for implementing drop-in replacements of the SourceFunction
-based data generators. Meanwhile, SourceFunction
is effectively superseded by the Source
interface and needs to be eventually deprecated. To fill this gap, this FLIP proposes the introduction of a generic data generator source based on FLIP-27 API.
Public Interfaces
The following
package org.apache.flink.api.connector.source.lib; /** * A data source that produces generators N events of an arbitrary type in parallel. This source is useful for * testing and for cases that just need a stream of N events of any kind. * * <p>The source splits the sequence into as many parallel sub-sequences as there are parallel * source readers. Each sub-sequence will be produced in order. Consequently, if the parallelism is * limited to one, this will produce one sequence in order. * * <p>This source is always bounded. For very long sequences user may want to consider executing * the application in a streaming manner, because, despite the fact that the produced stream is bounded, * the end bound is pretty far away. */ @Public public class DataGeneratorSource<OUT> implements Source<OUT, GeneratorSequenceSplit<OUT>, Collection<GeneratorSequenceSplit<OUT>>>, ResultTypeQueryable<OUT> { /** * Creates a new {@code DataGeneratorSource} that produces {@code count} records in * parallel. * * @param generatorFunction The generator function that receives index numbers and * translates them into events of the output type. * @param count The number of events to be produced. * @param typeInfo The type info of the returned events. */ public DataGeneratorSource( MapFunction<Long, OUT> generatorFunction, long count, TypeInformation<OUT> typeInfo) { ... }
Proposed Changes
Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.
Compatibility, Deprecation, and Migration Plan
- What impact (if any) will there be on existing users?
- If we are changing behavior how will we phase out the older behavior?
- If we need special migration tools, describe them here.
- When will we remove the existing behavior?
Test Plan
Describe in few sentences how the FLIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?
Rejected Alternatives
If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.