Is there a way to use a schema to convert avro messages from kafka with spark to dataframe? The schema file for user records:
{
"fields": [
{ "name": "firstName", "type": "string" },
{ "name": "lastName", "type": "string" }
],
"name": "user",
"type": "record"
}
And code snippets from SqlNetworkWordCount example and Kafka, Spark and Avro - Part 3, Producing and consuming Avro messages to read in messages.
object Injection {
val parser = new Schema.Parser()
val schema = parser.parse(getClass.getResourceAsStream("/user_schema.json"))
val injection: Injection[GenericRecord, Array[Byte]] = GenericAvroCodecs.toBinary(schema)
}
...
messages.foreachRDD((rdd: RDD[(String, Array[Byte])]) => {
val sqlContext = SQLContextSingleton.getInstance(rdd.sparkContext)
import sqlContext.implicits._
val df = rdd.map(message => Injection.injection.invert(message._2).get)
.map(record => User(record.get("firstName").toString, records.get("lastName").toString)).toDF()
df.show()
})
case class User(firstName: String, lastName: String)
Somehow I can't find another way than using a case class to convert AVRO messages to DataFrame. Is there a possibility to use the schema instead? I'm using Spark 1.6.2
and Kafka 0.10
.
The complete code, in case you're interested.
import com.twitter.bijection.Injection
import com.twitter.bijection.avro.GenericAvroCodecs
import kafka.serializer.{DefaultDecoder, StringDecoder}
import org.apache.avro.Schema
import org.apache.avro.generic.GenericRecord
import org.apache.spark.rdd.RDD
import org.apache.spark.sql.SQLContext
import org.apache.spark.streaming.kafka._
import org.apache.spark.streaming.{Seconds, StreamingContext, Time}
import org.apache.spark.{SparkConf, SparkContext}
object ReadMessagesFromKafka {
object Injection {
val parser = new Schema.Parser()
val schema = parser.parse(getClass.getResourceAsStream("/user_schema.json"))
val injection: Injection[GenericRecord, Array[Byte]] = GenericAvroCodecs.toBinary(schema)
}
def main(args: Array[String]) {
val brokers = "127.0.0.1:9092"
val topics = "test"
// Create context with 2 second batch interval
val sparkConf = new SparkConf().setAppName("ReadMessagesFromKafka").setMaster("local[*]")
val ssc = new StreamingContext(sparkConf, Seconds(2))
// Create direct kafka stream with brokers and topics
val topicsSet = topics.split(",").toSet
val kafkaParams = Map[String, String]("metadata.broker.list" -> brokers)
val messages = KafkaUtils.createDirectStream[String, Array[Byte], StringDecoder, DefaultDecoder](
ssc, kafkaParams, topicsSet)
messages.foreachRDD((rdd: RDD[(String, Array[Byte])]) => {
val sqlContext = SQLContextSingleton.getInstance(rdd.sparkContext)
import sqlContext.implicits._
val df = rdd.map(message => Injection.injection.invert(message._2).get)
.map(record => User(record.get("firstName").toString, records.get("lastName").toString)).toDF()
df.show()
})
// Start the computation
ssc.start()
ssc.awaitTermination()
}
}
/** Case class for converting RDD to DataFrame */
case class User(firstName: String, lastName: String)
/** Lazily instantiated singleton instance of SQLContext */
object SQLContextSingleton {
@transient private var instance: SQLContext = _
def getInstance(sparkContext: SparkContext): SQLContext = {
if (instance == null) {
instance = new SQLContext(sparkContext)
}
instance
}
}