Question

我试图将Apache Spark结构化流连接到MQTT主题（在本例中是IBM Bluemix上的IBM Watson IoT Platform）。

我按如下方式创建结构化流：

{
    "age" : "22",
    "gender" : "Male",
    "result" : "pass",
    "state" : "CA",
    "name": "Paul"
},
{
    "age" : "21",
    "gender" : "Female",
    "result" : "pass",
    "state" : "CA",
    "name": "Emily"
},

到目前为止一直很好，在REPL中我得到了这个df对象如下：

val df = spark.readStream 
    .format("org.apache.bahir.sql.streaming.mqtt.MQTTStreamSourceProvider")
    .option("username","<username>")
    .option("password","<password>")
    .option("clientId","a:vy0z2s:a-vy0z2s-zfzzckrnqf")
    .option("topic", "iot-2/type/WashingMachine/id/Washer02/evt/voltage/fmt/json")
    .load("tcp://vy0z2s.messaging.internetofthings.ibmcloud.com:1883")

但是如果我开始使用这一行从流中读取：

df: org.apache.spark.sql.DataFrame = [value: string, timestamp: timestamp]

我收到以下错误：

val query = df.writeStream
    .outputMode("append")
    .format("console")
    .start()

我的直觉表示架构有问题，所以我添加了一个：

scala> 17/02/03 07:32:23 ERROR StreamExecution: Query query-1
terminated with error java.lang.ClassCastException: scala.Tuple2
cannot be cast to scala.runtime.Nothing$    at
org.apache.bahir.sql.streaming.mqtt.MQTTTextStreamSource$$anonfun$getBatch$1$$anonfun$3.apply(MQTTStreamSource.scala:156)
    at
org.apache.bahir.sql.streaming.mqtt.MQTTTextStreamSource$$anonfun$getBatch$1$$anonfun$3.apply(MQTTStreamSource.scala:156)
    at scala.collection.MapLike$class.getOrElse(MapLike.scala:128)  at
scala.collection.concurrent.TrieMap.getOrElse(TrieMap.scala:633)    at
org.apache.bahir.sql.streaming.mqtt.MQTTTextStreamSource$$anonfun$getBatch$1.apply$mcZI$sp(MQTTStreamSource.scala:156)
    at
org.apache.bahir.sql.streaming.mqtt.MQTTTextStreamSource$$anonfun$getBatch$1.apply(MQTTStreamSource.scala:155)
    at
org.apache.bahir.sql.streaming.mqtt.MQTTTextStreamSource$$anonfun$getBatch$1.apply(MQTTStreamSource.scala:155)
    at scala.collection.immutable.Range.foreach(Range.scala:160)    at
org.apache.bahir.sql.streaming.mqtt.MQTTTextStreamSource.getBatch(MQTTStreamSource.scala:155)
    at
org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$5.apply(StreamExecution.scala:332)
    at
org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$5.apply(StreamExecution.scala:329)
    at
scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at
scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at scala.collection.Iterator$class.foreach(Iterator.scala:893)  at
scala.collection.AbstractIterator.foreach(Iterator.scala:1336)  at
scala.collection.IterableLike$class.foreach(IterableLike.scala:72)  at
org.apache.spark.sql.execution.streaming.StreamProgress.foreach(StreamProgress.scala:25)
    at
scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
    at
org.apache.spark.sql.execution.streaming.StreamProgress.flatMap(StreamProgress.scala:25)
    at
org.apache.spark.sql.execution.streaming.StreamExecution.org$apache$spark$sql$execution$streaming$StreamExecution$$runBatch(StreamExecution.scala:329)
    at
org.apache.spark.sql.execution.streaming.StreamExecution$$anonfun$org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches$1.apply$mcZ$sp(StreamExecution.scala:194)
    at
org.apache.spark.sql.execution.streaming.ProcessingTimeExecutor.execute(TriggerExecutor.scala:43)
    at
org.apache.spark.sql.execution.streaming.StreamExecution.org$apache$spark$sql$execution$streaming$StreamExecution$$runBatches(StreamExecution.scala:184)
    at
org.apache.spark.sql.execution.streaming.StreamExecution$$anon$1.run(StreamExecution.scala:120)
17/02/03 07:32:24 WARN MQTTTextStreamSource: Connection to mqtt server
lost. Connection lost (32109) - java.io.EOFException    at
org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:146)
    at java.lang.Thread.run(Thread.java:745) Caused by:
java.io.EOFException    at
java.io.DataInputStream.readByte(DataInputStream.java:267)  at
org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(MqttInputStream.java:65)
    at
org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:107)
    ... 1 more 17/02/03 07:32:28 WARN MQTTTextStreamSource: Connection to
mqtt server lost.

但这对任何想法都没有帮助吗？

Answer 1

您的问题似乎是因为您正在为后续连接重新使用相同的客户端ID

<div>Some text.</div>

每个clientID只允许一个唯一的连接;您不能使用相同的ID进行两个并发连接。

请检查客户端ID并确保同一应用的多个实例使用唯一的客户端ID。应用程序可以共享相同的API密钥，但MQTT要求客户端ID始终是唯一的。

ApacheSpahir上的ApacheBahir Stuctured Streaming连接器的架构问题

1 个答案: