Dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.3.1.2 O2: Java gateway process exited before sending its port number . . . . . . . . . . . 22 1.3.2 Usage issues . . . . . . . contains its own Python executable files and the installed Python packages. It is useful for local development to create a standalone Python environment and also useful when deploying a PyFlink job to production Local This page shows you how to set up PyFlink development environment in your local machine. This is usually used for local execution or development in an IDE. Set up Python environment It requires

Dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.3.1.2 O2: Java gateway process exited before sending its port number . . . . . . . . . . . 22 1.3.2 Usage issues . . . . . . . contains its own Python executable files and the installed Python packages. It is useful for local development to create a standalone Python environment and also useful when deploying a PyFlink job to production Local This page shows you how to set up PyFlink development environment in your local machine. This is usually used for local execution or development in an IDE. Set up Python environment It requires

that might be unbounded • we cannot store the entire stream in an accessible way • we have to process stream elements on-the-fly using limited memory 2 Vasiliki Kalavri | Boston University 2020 Properties ETL process complex fast and light-weight ETL: Extract-Transform-Load
 e.g. unzipping compressed files, data cleaning and standardization 6 Vasiliki Kalavri | Boston University 2020 1. Process events limitation on the stream: updates cannot change past entries in A. 11 Useful in theory for the development of streaming algorithms With limited practical value in distributed, real-world settings Vasiliki

selectivity > 1 • a filter operator typically has selectivity < 1 Is selectivity always known at development time? ??? Vasiliki Kalavri | Boston University 2020 Types of Parallelism 7 B A C A B D Satisfy deadlines: for applications with real-time constraints or QoS latency constraints. Batching Process multiple data elements in a single batch A A’ ??? Vasiliki Kalavri | Boston University 2020 43 separate processes, they communicate via permanent TCP connections. • If they run in the same process, the sender task serializes the outgoing records into a byte buffer. • A TaskManager needs one

Flink application. I highly recommend to start monitoring your Flink application early on in the development phase. This way you will be able to improve your dashboards and alerts over time and, more importantly importantly, observe the performance impact of the changes to your application throughout the development phase. By doing so, you can ask the right questions about the runtime behaviour of your application

reduce/aggregate/process(...) // specify the window function // define a non-keyed window-all operator stream .windowAll(...) // specify the window assigner .reduce/aggregate/process(...) // specify the seconds(1))) .process(new TemperatureAverager) val avgTemp = sensorData .keyBy(_.id) // shortcut for window.(TumblingEventTimeWindows.of(size)) .timeWindow(Time.seconds(1)) .process(new TemperatureAverager) windows every 15 minutes .window(SlidingEventTimeWindows.of(Time.hours(1), Time.minutes(15))) .process(new TemperatureAverager) val slidingAvgTemp = sensorData .keyBy(_.id) // shortcut for window

.window() .reduce|aggregate|process() stream. .windowAll() .reduce|aggregate|process() ◦TumblingEventTimeWindows.of(Time input = ... input .keyBy(“key”) .window(TumblingEventTimeWindows.of(Time.minutes(1))) .process(new MyWastefulMax()); public static class MyWastefulMax extends ProcessWindowFunction< SensorReading key type TimeWindow> { // window type @Override public void process( String key, Context context, Iterable events, Collector

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consumers can process events. 2 ??? Vasiliki Kalavri | Boston University 2020 Keeping up with the producers • Producers can generate events in a higher rate than the rate consumers can process events. with the producers • Producers can generate events in a higher rate than the rate consumers can process events. • What happens if consumers cannot keep up with the event rate? • drop messages 2 ?? with the producers • Producers can generate events in a higher rate than the rate consumers can process events. • What happens if consumers cannot keep up with the event rate? • drop messages • buffer

Java JDK. A Java JRE is not sufficient! • Apache Maven 3.x. • An IDE for Java and/or Scala development, such as IntelliJ IDEA (preferred), Eclipse, or Netbeans with appropriate plugins installed.

Checkpoints sent to JobManager's heap memory, i.e. the state is lost in case of failure • Use only for development and debugging purposes! FsStateBackend • Stores state on TaskManager’s heap but checkpoints it