Call a function with each element a stream in Databricks

Question

I have a DataFrame stream in Databricks, and I want to perform an action on each element. On the net I found specific purpose methods, like writing it to the console or dumping

Answer 1

Here is an example of reading using foreachBatch to save every item to redis using the streaming api.

Related to a previous question (DataFrame to RDD[(String, String)] conversion)

// import spark and spark-redis
import org.apache.spark._
import org.apache.spark.sql._
import org.apache.spark.streaming._
import org.apache.spark.sql.types._

import com.redislabs.provider.redis._

// schema of csv files
val userSchema = new StructType()
    .add("name", "string")
    .add("age", "string")

// create a data stream reader from a dir with csv files
val csvDF = spark
  .readStream
  .format("csv")
  .option("sep", ";")
  .schema(userSchema)
  .load("./data") // directory where the CSV files are 

// redis
val redisConfig = new RedisConfig(new RedisEndpoint("localhost", 6379))
implicit val readWriteConfig: ReadWriteConfig = ReadWriteConfig.Default

csvDF.map(r => (r.getString(0), r.getString(0))) // converts the dataset to a Dataset[(String, String)]
  .writeStream // create a data stream writer
  .foreachBatch((df, _) => sc.toRedisKV(df.rdd)(redisConfig)) // save each batch to redis after converting it to a RDD
  .start // start processing