集成spark结构化流与合流模式注册表

5kgi1eie 于 2021-05-22 发布在 Spark

关注(0)|答案(7)|浏览(362)

我在spark结构化流媒体中使用kafka源来接收融合编码的avro记录。我打算使用confluent schema registry，但与spark structured streaming的集成似乎是不可能的。
我已经看到了这个问题，但无法让它与合流模式注册表一起工作。使用spark 2.0.2（结构化流媒体）读取来自kafka的avro消息

avro apache-kafka apache-spark spark-structured-streaming confluent-schema-registry

来源：https://stackoverflow.com/questions/64346370/spark-structured-streaming-getting-garbage-on-reading-avro-data

7条答案

按热度按时间

wd2eg0qa1#

基于@cricket\u 007的答案，我创建了以下可以在集群环境中运行的解决方案，包括以下新特性：
您需要添加广播变量来将一些值传输到集群环境的Map操作中。schema.parser和kafkaavrodeserializer都不能在spark中序列化，因此需要在Map操作中初始化它们
我的结构化流使用foreachbatch输出接收器。
我应用org.apache.spark.sql.avro.schemaconverters将avro schema格式转换为spark structtype，这样您就可以在from\ json column函数中使用它来解析kafka主题字段（key和value）中的dataframe。
首先，您需要加载一些包：

SCALA_VERSION="2.11"
SPARK_VERSION="2.4.4"
CONFLUENT_VERSION="5.2.2"

jars=(
  "org.apache.spark:spark-sql-kafka-0-10_${SCALA_VERSION}:${SPARK_VERSION}"    ## format("kafka")
  "org.apache.spark:spark-avro_${SCALA_VERSION}:${SPARK_VERSION}"    ## SchemaConverters
  "io.confluent:kafka-schema-registry:${CONFLUENT_VERSION}"   ## import io.confluent.kafka.schemaregistry.client.rest.RestService
  "io.confluent:kafka-avro-serializer:${CONFLUENT_VERSION}"   ## import io.confluent.kafka.serializers.KafkaAvroDeserializer
)

./bin/spark-shell --packages ${"${jars[*]}"// /,}

以下是我在spark shell中测试的全部代码：

import org.apache.avro.Schema
import io.confluent.kafka.serializers.KafkaAvroDeserializer
import io.confluent.kafka.schemaregistry.client.rest.RestService

import org.apache.spark.sql.streaming.Trigger
import org.apache.spark.sql.DataFrame
import org.apache.spark.sql.functions._
import org.apache.spark.sql.types._
import org.apache.spark.sql.avro.SchemaConverters

import scala.collection.JavaConverters._
import java.time.LocalDateTime

spark.sparkContext.setLogLevel("Error")

val brokerServers = "xxx.yyy.zzz:9092"
val topicName = "mytopic" 
val schemaRegistryURL = "http://xxx.yyy.zzz:8081"

val restService = new RestService(schemaRegistryURL)

val exParser = new Schema.Parser
//-- For both key and value
val schemaNames = Seq("key", "value")
val schemaStrings = schemaNames.map(i => (i -> restService.getLatestVersion(s"$topicName-$i").getSchema)).toMap
val tempStructMap = schemaStrings.transform((k,v) => SchemaConverters.toSqlType(exParser.parse(v)).dataType)
val schemaStruct = new StructType().add("key", tempStructMap("key")).add("value", tempStructMap("value"))
//-- For key only 
// val schemaStrings = restService.getLatestVersion(s"$topicName-key").getSchema
// val schemaStruct = SchemaConverters.toSqlType(exParser.parse(schemaStrings)).dataType
//-- For value only 
// val schemaStrings = restService.getLatestVersion(s"$topicName-value").getSchema
// val schemaStruct = SchemaConverters.toSqlType(exParser.parse(schemaStrings)).dataType

val query = spark
  .readStream
  .format("kafka")
  .option("kafka.bootstrap.servers", brokerServers)
  .option("subscribe", topicName)
  .load()
  .writeStream
  .outputMode("append")
  //.option("checkpointLocation", s"cos://$bucket.service/checkpoints/$tableName")
  .foreachBatch((batchDF: DataFrame, batchId: Long) => {

    val bcTopicName = sc.broadcast(topicName)
    val bcSchemaRegistryURL = sc.broadcast(schemaRegistryURL)
    val bcSchemaStrings = sc.broadcast(schemaStrings)

    val rstDF = batchDF.map {
      row =>

        val props = Map("schema.registry.url" -> bcSchemaRegistryURL.value)
        //-- For both key and value
        val isKeys =  Map("key" -> true, "value" -> false)
        val deserializers = isKeys.transform{ (k,v) => 
            val des = new KafkaAvroDeserializer
            des.configure(props.asJava, v)
            des 
        }
        //-- For key only 
        // val deserializer = new KafkaAvroDeserializer
        // deserializer.configure(props.asJava, true)
        //-- For value only 
        // val deserializer = new KafkaAvroDeserializer
        // deserializer.configure(props.asJava, false)

        val inParser = new Schema.Parser
        //-- For both key and value
        val values = bcSchemaStrings.value.transform( (k,v) => 
            deserializers(k).deserialize(bcTopicName.value, row.getAs[Array[Byte]](k), inParser.parse(v)).toString)
        s"""{"key": ${values("key")}, "value": ${values("value")} }"""
        //-- For key only 
        // deserializer.deserialize(bcTopicName.value, row.getAs[Array[Byte]]("key"), inParser.parse(bcSchemaStrings.value)).toString
        //-- For value only 
        // deserializer.deserialize(bcTopicName.value, row.getAs[Array[Byte]]("value"), inParser.parse(bcSchemaStrings.value)).toString  
      }
      .select(from_json(col("value"), schemaStruct).as("root"))
      .select("root.*")

    println(s"${LocalDateTime.now} --- Batch $batchId: ${rstDF.count} rows")
    rstDF.printSchema
    rstDF.show(false)    

  })
  .trigger(Trigger.ProcessingTime("60 seconds"))
  .start()

query.awaitTermination()

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brvekthn2#

我花了几个月的时间阅读源代码并进行测试。简而言之，spark只能处理字符串和二进制序列化。必须手动反序列化数据。在spark中，创建合流rest服务对象以获取模式。使用avro解析器将响应对象中的模式字符串转换为avro模式。接下来，照常读Kafka的主题。然后用合流的kafkaavrodeserializerMap二进制类型的“value”列。我强烈建议进入这些类的源代码，因为这里有很多内容，所以为了简洁起见，我将省略许多细节。

//Used Confluent version 3.2.2 to write this. 
import io.confluent.kafka.schemaregistry.client.rest.RestService
import io.confluent.kafka.serializers.KafkaAvroDeserializer
import org.apache.avro.Schema

case class DeserializedFromKafkaRecord(key: String, value: String)

val schemaRegistryURL = "http://127.0.0.1:8081"

val topicName = "Schema-Registry-Example-topic1"
val subjectValueName = topicName + "-value"

//create RestService object
val restService = new RestService(schemaRegistryURL)

//.getLatestVersion returns io.confluent.kafka.schemaregistry.client.rest.entities.Schema object.
val valueRestResponseSchema = restService.getLatestVersion(subjectValueName)

//Use Avro parsing classes to get Avro Schema
val parser = new Schema.Parser
val topicValueAvroSchema: Schema = parser.parse(valueRestResponseSchema.getSchema)

//key schema is typically just string but you can do the same process for the key as the value
val keySchemaString = "\"string\""
val keySchema = parser.parse(keySchemaString)

//Create a map with the Schema registry url.
//This is the only Required configuration for Confluent's KafkaAvroDeserializer.
val props = Map("schema.registry.url" -> schemaRegistryURL)

//Declare SerDe vars before using Spark structured streaming map. Avoids non serializable class exception.
var keyDeserializer: KafkaAvroDeserializer = null
var valueDeserializer: KafkaAvroDeserializer = null

//Create structured streaming DF to read from the topic.
val rawTopicMessageDF = sql.readStream
  .format("kafka")
  .option("kafka.bootstrap.servers", "127.0.0.1:9092")
  .option("subscribe", topicName)
  .option("startingOffsets", "earliest")
  .option("maxOffsetsPerTrigger", 20)  //remove for prod
  .load()

//instantiate the SerDe classes if not already, then deserialize!
val deserializedTopicMessageDS = rawTopicMessageDF.map{
  row =>
    if (keyDeserializer == null) {
      keyDeserializer = new KafkaAvroDeserializer
      keyDeserializer.configure(props.asJava, true)  //isKey = true
    }
    if (valueDeserializer == null) {
      valueDeserializer = new KafkaAvroDeserializer
      valueDeserializer.configure(props.asJava, false) //isKey = false
    }

    //Pass the Avro schema.
    val deserializedKeyString = keyDeserializer.deserialize(topicName, row.key, keySchema).toString //topic name is actually unused in the source code, just required by the signature. Weird right?
    val deserializedValueString = valueDeserializer.deserialize(topicName, row.value, topicValueAvroSchema).toString

    DeserializedFromKafkaRecord(deserializedKeyString, deserializedValueString)
}

val deserializedDSOutputStream = deserializedTopicMessageDS.writeStream
    .outputMode("append")
    .format("console")
    .option("truncate", false)
    .start()

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zhte4eai3#

对于任何想做这件事的人 pyspark ：之前felipe引用的库在jvm上运行得很好，所以我编写了一个小 Package 函数，将它集成到python中。这看起来非常粗糙，因为scala语言中的很多隐式类型都必须在py4j中显式指定。到目前为止，即使是在spark 2.4.1中，它也运行得很好。

def expand_avro(spark_context, sql_context, data_frame, schema_registry_url, topic):
    j = spark_context._gateway.jvm
    dataframe_deserializer = j.za.co.absa.abris.avro.AvroSerDe.DataframeDeserializer(data_frame._jdf)
    naming_strategy = getattr(
        getattr(j.za.co.absa.abris.avro.read.confluent.SchemaManager,
                "SchemaStorageNamingStrategies$"), "MODULE$").TOPIC_NAME()
    conf = getattr(getattr(j.scala.collection.immutable.Map, "EmptyMap$"), "MODULE$")
    conf = getattr(conf, "$plus")(j.scala.Tuple2("schema.registry.url", schema_registry_url))
    conf = getattr(conf, "$plus")(j.scala.Tuple2("schema.registry.topic", topic))
    conf = getattr(conf, "$plus")(j.scala.Tuple2("value.schema.id", "latest"))
    conf = getattr(conf, "$plus")(j.scala.Tuple2("value.schema.naming.strategy", naming_strategy))
    schema_path = j.scala.Option.apply(None)
    conf = j.scala.Option.apply(conf)
    policy = getattr(j.za.co.absa.abris.avro.schemas.policy.SchemaRetentionPolicies, "RETAIN_SELECTED_COLUMN_ONLY$")()
    data_frame = dataframe_deserializer.fromConfluentAvro("value", schema_path, conf, policy)
    data_frame = DataFrame(data_frame, sql_context)
    return data_frame

为此，您必须将库添加到spark包中，例如。

os.environ['PYSPARK_SUBMIT_ARGS'] = '--packages ' \
    'org.apache.spark:spark-sql-kafka-0-10_2.11:2.4.1,' \
    'org.apache.spark:spark-avro_2.11:2.4.1,' \
    'za.co.absa:abris_2.11:2.2.2 ' \
    '--repositories https://packages.confluent.io/maven/ ' \
    'pyspark-shell'

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5q4ezhmt4#

由于另一个最有用的答案被删除了，我想重新添加一些重构和注解。
以下是所需的依赖项。

<dependency>
            <groupId>io.confluent</groupId>
            <artifactId>kafka-avro-serializer</artifactId>
            <version>${confluent.version}</version>
            <exclusions> 
                <!-- Conflicts with Spark's version -->
                <exclusion> 
                    <groupId>org.apache.kafka</groupId>
                    <artifactId>kafka-clients</artifactId>
                </exclusion>
            </exclusions>
     </dependency>

    <dependency>
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-sql-kafka-0-10_${scala.version}</artifactId>
        <version>${spark.version}</version>
    </dependency>

    <dependency>
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-avro_${scala.version}</artifactId>
        <version>${spark.version}</version>
    </dependency>

下面是scala实现（仅在本地测试） master=local[*] )
第一部分，定义导入、一些字段和一些helper方法来获取模式

import io.confluent.kafka.schemaregistry.client.{CachedSchemaRegistryClient, SchemaRegistryClient}
import io.confluent.kafka.serializers.AbstractKafkaAvroDeserializer
import org.apache.avro.Schema
import org.apache.avro.generic.GenericRecord
import org.apache.commons.cli.CommandLine
import org.apache.spark.sql._
import org.apache.spark.sql.avro.SchemaConverters
import org.apache.spark.sql.streaming.OutputMode

object App {

  private var schemaRegistryClient: SchemaRegistryClient = _

  private var kafkaAvroDeserializer: AvroDeserializer = _

  def lookupTopicSchema(topic: String, isKey: Boolean = false) = {
    schemaRegistryClient.getLatestSchemaMetadata(topic + (if (isKey) "-key" else "-value")).getSchema
  }

  def avroSchemaToSparkSchema(avroSchema: String) = {
    SchemaConverters.toSqlType(new Schema.Parser().parse(avroSchema))
  }

 // ... continues below

然后定义一个简单的main方法来解析cmd参数以获得kafka的详细信息

def main(args: Array[String]): Unit = {
    val cmd: CommandLine = parseArg(args)

    val master = cmd.getOptionValue("master", "local[*]")
    val spark = SparkSession.builder()
      .appName(App.getClass.getName)
      .master(master)
      .getOrCreate()

    val bootstrapServers = cmd.getOptionValue("bootstrap-server")
    val topic = cmd.getOptionValue("topic")
    val schemaRegistryUrl = cmd.getOptionValue("schema-registry")

    consumeAvro(spark, bootstrapServers, topic, schemaRegistryUrl)

    spark.stop()
  }

  // ... still continues

然后，对Kafka主题进行消费和反序列化的重要方法

private def consumeAvro(spark: SparkSession, bootstrapServers: String, topic: String, schemaRegistryUrl: String): Unit = {
    import spark.implicits._

    // Setup the Avro deserialization UDF
    schemaRegistryClient = new CachedSchemaRegistryClient(schemaRegistryUrl, 128)
    kafkaAvroDeserializer = new AvroDeserializer(schemaRegistryClient) 
    spark.udf.register("deserialize", (bytes: Array[Byte]) =>
      kafkaAvroDeserializer.deserialize(bytes)
    )

    // Load the raw Kafka topic (byte stream)
    val rawDf = spark.readStream
      .format("kafka")
      .option("kafka.bootstrap.servers", bootstrapServers)
      .option("subscribe", topic)
      .option("startingOffsets", "earliest")
      .load()

    // Deserialize byte stream into strings (Avro fields become JSON)
    import org.apache.spark.sql.functions._
    val jsonDf = rawDf.select(
      // 'key.cast(DataTypes.StringType),  // string keys are simplest to use
      callUDF("deserialize", 'key).as("key"), // but sometimes they are avro
      callUDF("deserialize", 'value).as("value")
      // excluding topic, partition, offset, timestamp, etc
    )

    // Get the Avro schema for the topic from the Schema Registry and convert it into a Spark schema type
    val dfValueSchema = {
      val rawSchema = lookupTopicSchema(topic)
      avroSchemaToSparkSchema(rawSchema)
    }

    // Apply structured schema to JSON stream
    val parsedDf = jsonDf.select(
      'key, // keys are usually plain strings
      // values are JSONified Avro records
      from_json('value, dfValueSchema.dataType).alias("value")
    ).select(
      'key,
      $"value.*" // flatten out the value
    )

    // parsedDf.printSchema()

    // Sample schema output
    // root
    // |-- key: string (nullable = true)
    // |-- header: struct (nullable = true)
    // |    |-- time: long (nullable = true)
    // |    ...

    // TODO: Do something interesting with this stream
    parsedDf.writeStream
      .format("console")
      .outputMode(OutputMode.Append())
      .option("truncate", false)
      .start()
      .awaitTermination()
  }

 // still continues

命令行解析器允许传入引导服务器、模式注册表、主题名和spark master。

private def parseArg(args: Array[String]): CommandLine = {
    import org.apache.commons.cli._

    val options = new Options

    val masterOption = new Option("m", "master", true, "Spark master")
    masterOption.setRequired(false)
    options.addOption(masterOption)

    val bootstrapOption = new Option("b", "bootstrap-server", true, "Bootstrap servers")
    bootstrapOption.setRequired(true)
    options.addOption(bootstrapOption)

    val topicOption = new Option("t", "topic", true, "Kafka topic")
    topicOption.setRequired(true)
    options.addOption(topicOption)

    val schemaRegOption = new Option("s", "schema-registry", true, "Schema Registry URL")
    schemaRegOption.setRequired(true)
    options.addOption(schemaRegOption)

    val parser = new BasicParser
    parser.parse(options, args)
  }

  // still continues

为了让上面的udf工作，那么就需要一个反序列化器来将字节的Dataframe转换成包含反序列化avro的Dataframe

// Simple wrapper around Confluent deserializer
  class AvroDeserializer extends AbstractKafkaAvroDeserializer {
    def this(client: SchemaRegistryClient) {
      this()
      // TODO: configure the deserializer for authentication 
      this.schemaRegistry = client
    }

    override def deserialize(bytes: Array[Byte]): String = {
      val value = super.deserialize(bytes)
      value match {
        case str: String =>
          str
        case _ =>
          val genericRecord = value.asInstanceOf[GenericRecord]
          genericRecord.toString
      }
    }
  }

} // end 'object App'

把这些块放在一起，它在添加后在intellij中工作 -b localhost:9092 -s http://localhost:8081 -t myTopic 运行配置>程序参数

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q9yhzks05#

这个图书馆将为你做这项工作。它通过spark结构化流连接到合流模式注册表。
对于confluent，它处理与有效负载一起发送的模式id。
在自述文件中，您将找到一段代码片段，说明如何执行此操作。
披露：我为absa工作，我开发了这个图书馆。

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ecbunoof6#

这是我将spark结构化流与kafka和schema registry（scala中的代码）集成在一起的代码示例

import org.apache.spark.sql.SparkSession
import io.confluent.kafka.schemaregistry.client.rest.RestService // <artifactId>kafka-schema-registry</artifactId>
import org.apache.spark.sql.avro.from_avro // <artifactId>spark-avro_${scala.compat.version}</artifactId>
import org.apache.spark.sql.functions.col

object KafkaConsumerAvro {

  def main(args: Array[String]): Unit = {

    val KAFKA_BOOTSTRAP_SERVERS = "localhost:9092"
    val SCHEMA_REGISTRY_URL = "http://localhost:8081"
    val TOPIC = "transactions"

    val spark: SparkSession = SparkSession.builder().appName("KafkaConsumerAvro").getOrCreate()
    spark.sparkContext.setLogLevel("ERROR")

    val df = spark.readStream
      .format("kafka")
      .option("kafka.bootstrap.servers", KAFKA_BOOTSTRAP_SERVERS)
      .option("subscribe", TOPIC)
      .option("startingOffsets", "earliest") // from starting
      .load()

//     Prints Kafka schema with columns (topic, offset, partition e.t.c)
    df.printSchema()

//    Create REST service to access schema registry and retrieve topic schema (latest)
    val restService = new RestService(SCHEMA_REGISTRY_URL)
    val valueRestResponseSchema = restService.getLatestVersion(TOPIC + "-value")
    val jsonSchema = valueRestResponseSchema.getSchema

    val transactionDF = df.select(
      col("key").cast("string"), // cast to string from binary value
      from_avro(col("value"), jsonSchema).as("transaction"), // convert from avro value
      col("topic"),
      col("offset"),
      col("timestamp"),
      col("timestampType"))
    transactionDF.printSchema()

//    Stream data to console for testing
    transactionDF.writeStream
      .format("console")
      .outputMode("append")
      .start()
      .awaitTermination()
  }

}

<!-- READ AND WRITE AVRO DATA -->
<dependency>
  <groupId>org.apache.spark</groupId>
  <artifactId>spark-avro_${scala.compat.version}</artifactId>
  <version>${spark.version}</version>
</dependency>
<!-- INTEGRATION WITH SCHEMA REGISTRY -->
<dependency>
  <groupId>io.confluent</groupId>
  <artifactId>kafka-schema-registry</artifactId>
  <version>${confluent.version}</version>
</dependency>

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nx7onnlm7#

databricks现在提供此功能，但您必须为此付费：-(

dataDF
  .select(
    to_avro($"key", lit("t-key"), schemaRegistryAddr).as("key"),
    to_avro($"value", lit("t-value"), schemaRegistryAddr).as("value"))
  .writeStream
  .format("kafka")
  .option("kafka.bootstrap.servers", servers)
  .option("topic", "t")
  .save()

请参见：https://docs.databricks.com/spark/latest/structured-streaming/avro-dataframe.html 更多信息
一个好的免费选择是阿布里斯。请参见：https://github.com/absaoss/abris 我们可以看到的唯一缺点是，您需要在运行时提供avro模式的文件，以便框架可以在将其发布到kafka主题之前在您的Dataframe上实施此模式。

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集成spark结构化流与合流模式注册表

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