PySpark：将 Spark Dataframe 写入 Kafka 主题

Question

Am trying to load dataframe to Kafka Topic. Am getting error on selecting the key and value. Any suggestion would be helpful.

Below is my code,

data = spark.sql('select * from job')

kafka = data.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)")\
    .writeStream.outputMode(outputMode='Append').format('kafka')\
    .option("kafka.bootstrap.servers", "localhost:9092")\
    .option("topic", "Jim_Topic")\
    .option("checkpointLocation", "C:/Hadoop/Data/CheckPointLocation/")\
    .start()

kafka.awaitTermination()

Below is the error,

pyspark.sql.utils.AnalysisException: cannot resolve '`key`' given input columns: [job.JOB_ID, 
job.JOB_TITLE, job.MAX_SALARY, job.MIN_SALARY]; line 1 pos 5;
'Project [unresolvedalias(cast('key as string), None), unresolvedalias(cast('value as string), None)]
+- Project [JOB_ID#0, JOB_TITLE#1, MIN_SALARY#2, MAX_SALARY#3]
   +- SubqueryAlias `job`
      +- StreamingRelation

DataSource(org.apache.spark.sql.SparkSession@1f3fc47a,csv,List(),Some(StructType(StructField(JOB_ID,StringType,true), StructField(JOB_TITLE,StringType,true), StructField(MIN_SALARY,StringType,true), StructField(MAX_SALARY,StringType,true))),List(),None,Map(sep ->,, header -> false, path -> C:/Hadoop/Data/Job*.csv),None), FileSource[C:/Hadoop/Data/Job*.csv], [JOB_ID#0, JOB_TITLE#1, MIN_SALARY#2, MAX_SALARY#3]

Answer 1

Tried converting the values into json, it worked perfectly. Now am able to send the messages from spark stream to kafka,

kafka = data.selectExpr("CAST(JOB_ID AS STRING) AS key", "to_json(struct(*)) AS value")\