pythonapache-sparkpysparkspark-structured-streaming

Using PySpark Structured Streaming, How to Send Processed Data to Client Through WebSocket


I'm using on a PySpark Structured Streaming in my application where I use readStream to read appended data from an Apache Iceberg table. After processing the data within the PySpark framework, I want to send the processed data to a WebSocket client using the websockets library in Python.

I tried using .foreach(), but I could not use await inside it


Solution

  • I found a solution:

    1. Define the asynchronous processing function:
    async def process(df, df_id, websocket):
        # data processing
        await websocket.send(data)
    
    1. Create a wrapper function to process each batch of streaming data:
    def process_wrapper(batch_df, batch_id, websocket):
        asyncio.run(process(batch_df, batch_id, websocket))
    
    1. Set up the streaming query:
    query = df \
           .writeStream \
           .outputMode("append") \
           .foreachBatch(partial(process_wrapper, websocket=websocket)) \
           .trigger(processingTime="10 seconds") \
           .start()