A library for reading data from MQTT Servers using Spark SQL Streaming ( or Structured streaming.).
Using SBT:
libraryDependencies += "org.apache.bahir" %% "spark-sql-streaming-mqtt" % "2.0.0"
Using Maven:
<dependency> <groupId>org.apache.bahir</groupId> <artifactId>spark-sql-streaming-mqtt_2.11</artifactId> <version>2.0.0</version> </dependency>
This library can also be added to Spark jobs launched through spark-shell
or spark-submit
by using the --packages
command line option. For example, to include it when starting the spark shell:
$ bin/spark-shell --packages org.apache.bahir:spark-sql-streaming-mqtt_2.11:2.0.0
Unlike using --jars
, using --packages
ensures that this library and its dependencies will be added to the classpath. The --packages
argument can also be used with bin/spark-submit
.
This library is compiled for Scala 2.11 only, and intends to support Spark 2.0 onwards.
A SQL Stream can be created with data streams received through MQTT Server using,
sqlContext.readStream .format("org.apache.bahir.sql.streaming.mqtt.MQTTStreamSourceProvider") .option("topic", "mytopic") .load("tcp://localhost:1883")
Setting values for option localStorage
and clientId
helps in recovering in case of a restart, by restoring the state where it left off before the shutdown.
sqlContext.readStream .format("org.apache.bahir.sql.streaming.mqtt.MQTTStreamSourceProvider") .option("topic", "mytopic") .option("localStorage", "/path/to/localdir") .option("clientId", "some-client-id") .load("tcp://localhost:1883")
An example, for scala API to count words from incoming message stream.
// Create DataFrame representing the stream of input lines from connection to mqtt server val lines = spark.readStream .format("org.apache.bahir.sql.streaming.mqtt.MQTTStreamSourceProvider") .option("topic", topic) .load(brokerUrl).as[(String, Timestamp)] // Split the lines into words val words = lines.map(_._1).flatMap(_.split(" ")) // Generate running word count val wordCounts = words.groupBy("value").count() // Start running the query that prints the running counts to the console val query = wordCounts.writeStream .outputMode("complete") .format("console") .start() query.awaitTermination()
Please see MQTTStreamWordCount.scala
for full example.
An example, for Java API to count words from incoming message stream.
// Create DataFrame representing the stream of input lines from connection to mqtt server. Dataset<String> lines = spark .readStream() .format("org.apache.bahir.sql.streaming.mqtt.MQTTStreamSourceProvider") .option("topic", topic) .load(brokerUrl).select("value").as(Encoders.STRING()); // Split the lines into words Dataset<String> words = lines.flatMap(new FlatMapFunction<String, String>() { @Override public Iterator<String> call(String x) { return Arrays.asList(x.split(" ")).iterator(); } }, Encoders.STRING()); // Generate running word count Dataset<Row> wordCounts = words.groupBy("value").count(); // Start running the query that prints the running counts to the console StreamingQuery query = wordCounts.writeStream() .outputMode("complete") .format("console") .start(); query.awaitTermination();
Please see JavaMQTTStreamWordCount.java
for full example.