Scotty: Efficient Window Aggregation for out-of-order Stream Processing

This repository provides Scotty, a framework for efficient window aggregations for out-of-order Stream Processing.

Features:

• High performance window aggregation with stream slicing.
• Scales to thousands of concurrent windows.
• Support for Tumbling, Sliding, and Session Windows.
• Initial support for Count based windows.
• Out-of-order processing.
• Aggregate Sharing among all concurrent windows.
• Connector for Apache Flink.

Resources:

• Paper: Efficient Window Aggregation with General Stream Slicing (EDBT 2019, Best Paper)
• Paper: Scotty: Efficient Window Aggregation for out-of-order Stream Processing (ICDE 2018)
• Presentations Slides FlinkForward 2018
• API Documentation

Flink Integration Example:

// Instantiate Scotty window operator
KeyedScottyWindowOperator<Tuple, Tuple2<Integer, Integer>, Tuple2<Integer, Integer>> windowOperator =
new KeyedScottyWindowOperator<>(new SumWindowFunction());

// Add multiple windows to the same operator
windowOperator.addWindow(new TumblingWindow(WindowMeasure.Time, 1000));
windowOperator.addWindow(new SlidingWindow(WindowMeasure.Time, 1000, 5000));
windowOperator.addWindow(new SessionWindow(1000));

// Add count based window
windowOperator.addWindow(new TumblingWindow(WindowMeasure.Count, 1000))

// Add operator to Flink job
stream.keyBy(0)
      .process(windowOperator)

Benchmark:

Throughput in comparison to the Flink standard window operator (Window Buckets) for Sliding Event-Time Windows:
We fix the window size to 60 seconds and modify the slide size. If the slide size gets smaller, Flink has to maintain a higher number of overlapping (concurrent) windows.

Throughput in comparison to Flink for concurrent Tumbling Windows:

Roadmap:

We plan to extend our framework with the following features:

• Support for User-Defined windows
• User-defined window measures
• Support for Refinements
• Connector for Apache Beam
• Support of Flink Checkpoints and State Backends

Setup:

The maven package is currently not publically available. Therefore we have to build it from source:

git clone git@github.com:TU-Berlin-DIMA/scotty-window-processor.git

mvn clean install

Then you can use the library in your maven project.

<dependency> 
 <groupId>de.tub.dima.scotty</groupId>
 <artifactId>flink-connector</artifactId>
 <version>0.3</version>
</dependency>

Efficient Window Aggregation with General Stream Sliching at EDBT 2019

General Stream Slicing received the Best Paper Award at the 22nd International Conference on Extending Database Technology in March 2019.

Abstract:
Window aggregation is a core operation in data stream processing. Existing aggregation techniques focus on reducing latency, eliminating redundant computations, and minimizing memory usage. However, each technique operates under different assumptions with respect to workload characteristics such as properties of aggregation functions (e.g., invertible, associative), window types (e.g., sliding, sessions), windowing measures (e.g., time- or countbased), and stream (dis)order. Violating the assumptions of a technique can deem it unusable or drastically reduce its performance. In this paper, we present the first general stream slicing technique for window aggregation. General stream slicing automatically adapts to workload characteristics to improve performance without sacrificing its general applicability. As a prerequisite, we identify workload characteristics which affect the performance and applicability of aggregation techniques. Our experiments show that general stream slicing outperforms alternative concepts by up to one order of magnitude.

• Paper: Efficient Window Aggregation with General Stream Sliching

• BibTeX citation:

@inproceedings{traub2019efficient,
  title={Efficient Window Aggregation with General Stream Slicing},
  author={Traub, Jonas and Grulich, Philipp M. and Cu{\'e}llar, Alejandro Rodr{\'\i}guez and Bre{\ss}, Sebastian and Katsifodimos, Asterios and Rabl, Tilmann and Markl, Volker},
  booktitle={22th International Conference on Extending Database Technology (EDBT)},
  year={2019}
}

Acknowledgements: This work was funded by the EU project E2Data (780245), Delft Data Science, and the German Ministry for Education and Research as BBDC I (01IS14013A) and BBDC II (01IS18025A)

Scotty: Efficient Window Aggregation for out-of-order Stream Processing at ICDE 2018

Scotty was first published at the 34th IEEE International Conference on Data Engineering in April 2018.

Abstract:
Computing aggregates over windows is at the core of virtually every stream processing job. Typical stream processing applications involve overlapping windows and, therefore, cause redundant computations. Several techniques prevent this redundancy by sharing partial aggregates among windows. However, these techniques do not support out-of-order processing and session windows. Out-of-order processing is a key requirement to deal with delayed tuples in case of source failures such as temporary sensor outages. Session windows are widely used to separate different periods of user activity from each other. In this paper, we present Scotty, a high throughput operator for window discretization and aggregation. Scotty splits streams into non-overlapping slices and computes partial aggregates per slice. These partial aggregates are shared among all concurrent queries with arbitrary combinations of tumbling, sliding, and session windows. Scotty introduces the first slicing technique which (1) enables stream slicing for session windows in addition to tumbling and sliding windows and (2) processes out-of-order tuples efficiently. Our technique is generally applicable to a broad group of dataflow systems which use a unified batch and stream processing model. Our experiments show that we achieve a throughput an order of magnitude higher than alternative stateof-the-art solutions.

• Paper: Scotty: Efficient Window Aggregation for out-of-order Stream Processing

• BibTeX citation:

@inproceedings{traub2018scotty,
  title={Scotty: Efficient Window Aggregation for out-of-order Stream Processing},
  author={Traub, Jonas and Grulich, Philipp M. and Cuellar, Alejandro Rodríguez and Breß, Sebastian and Katsifodimos, Asterios and Rabl, Tilmann and Markl, Volker},
  booktitle={34th IEEE International Conference on Data Engineering (ICDE)},
  year={2018}
}

Acknoledgements: This work was supported by the EU projects Proteus (687691) and Streamline (688191), DFG Stratosphere (606902), and the German Ministry for Education and Research as BBDC (01IS14013A) and Software Campus (01IS12056).