How to configure flink jobs at runtime?

Question

Is it possible to configure a flink application at runtime? For example, I have a streaming application that reads the input, does some transformations and then filters out all the elements below a certain threshold. However, I want this threshold to be configurable at runtime, meaning I'm able to change this without having to restart my flink job. Example code:

DataStream<MyModel> myModelDataStream = // get input ...
  // do some stuff ...
  .filter(new RichFilterFunction<MyModel>() {
    @Override
    public boolean filter(MyModel value) throws Exception {
      return value.someValue() > someGlobalState.getThreshold();
    }
  })
  
// write to some sink ...
DataStream<MyConfig> myConfigDataStream = // get input ...
  // ...
  .process(new RichProcessFunction<MyConfig>() {
    someGlobalState.setThreshold(MyConfig.getThreshold());
  })

// ...

Is there some possibility to achive this? Like a global state that can be changed through a configuration stream for example.

Answer 1

Yes, you can do this with a BroadcastProcessFunction. Something roughly like this:

MapStateDescriptor<Void, Threshold> bcStateDescriptor = 
  new MapStateDescriptor<>("thresholds", Types.VOID, Threshold.class);

DataStream<MyModel> myModelDataStream = // get input ...
DataStream<Threshold> thresholds = // get input...
BroadcastStream<Threshold> controlStream = thresholds.broadcast(bcStateDescriptor);

DataStream<MyModel> result = myModelDataStream
  .connect(controlStream)
  .process(new MyFunction());

public class MyFunction extends BroadcastProcessFunction<MyModel, Long, MyModel> {    
  @Override
  public void processBroadcastElement(Threshold newthreshold, Context ctx, Collector<MyModel> out) {
    MapStateDescriptor stateDescriptor = new MapStateDescriptor<>("thresholds", Types.VOID, Threshold.class)
    BroadcastState<Void, Threshold> bcState = ctx.getBroadcastState(stateDescriptor);  
    bcState.put(null, newthreshold);
  }

  @Override
  public void processElement(MyModel model, Collector<MyModel> out) {
    Threshold threshold = ctx.getBroadcastState(new MapStateDescriptor<>("threshold", Types.VOID, Threshold.class)).get(null);
    if (threshold.value() == null || model.getData() > threshold.value()) {
      out.collect(model);
    }
  }
}