Big Data

Apache Flink – Highly Scalable Streaming Engine

Why Flink: more scalable than Storm upto more than 1000s of nodes( massive scale) more fault tolerant than Storm maintain “state snapshots” to guarantee exactly once processing In […]

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Mohd Naeem
  • Why Flink:
    • more scalable than Storm upto more than 1000s of nodes( massive scale)
    • more fault tolerant than Storm
      • maintain “state snapshots” to guarantee exactly once processing
    • In similarity, it is also based on event based streaming like Storm
  • Flink Vs Spark Streaming Vs Storm:
    • Faster than Storm
    • real time streaming like Storm
    • event based like storm and maintains windowing
    • exactly once guarantee is good for financial applications
  • Flink Architecture:
    • Flink can sit on the top of a local or standalone or a cluster based Hadoop system or even on the cloud on AWS or Google Cloud
    • Flink has 2 distinct set of APOs – Data Streaming APIs( more like Storm) as well as Data Set APIs( more like Spark Streaming)
    • In its each universe –
      • Data Streaming APIs support Event based processing as well as SQL/Table based processing.
      • Data Set APIs support FlinkML, Gelly and SQL/Table based processing
    • exIhw
    • Connectors for Flink – HDFS, Kafka, Cassandra, RabbitMQ, Redis, Elastic search, NIFI etc
  • Lets play with Flink:
    • Login to the console using maria_dev credentials and elevate to root permissions.
    • Download Apache Flink from apache.flink.org. Download using this link – wget https://archive.apache.org/dist/flink/flink-1.2.0/flink-1.2.0-bin-hadoop27-scala_2.10.tgz
    • exIhw
    • Unzip the downloadable – tar xvf flink-1.2.0-bin-hadoop27-scala_2.10.tgz
    • Move to the flink folder – cd flink-1.2.0
    • Now first lets configure the config files – cd conf
    • Edit – nano flink-conf.yaml
      • jobmanager.web.port: 8081 to jobmanager.web.port: 8082
    • Now lets start flink – go to flink’s bin folder and run
      • ./start-local.sh
    • exIhw
    • Now lets open the Flink WEb UI – http://127.0.0.1:8082
    • exIhw
    • Now lets run one example from GitHub location – wget https://raw.githubusercontent.com/apache/flink/master/flink-examples/flink-examples-streaming/src/main/scala/org/apache/flink/streaming/scala/examples/socket/SocketWindowWordCount.scala
    • here is the heart of the code.
      • You first get the streaming env –
        • // get the execution environment
          val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment
      • Then you process and transform the data –
        • // parse the data, group it, window it, and aggregate the counts
          val windowCounts = text
          .flatMap { w => w.split(“\\s”) }
          .map { w => WordWithCount(w, 1) }
          .keyBy(“word”)
          .timeWindow(Time.seconds(5))
          .sum(“count”)
    • exIhw
    • Now lets open up a port and listen on port 9000 – nc -l 9000
    • Now run the example –
      • go to /home/maria_dev/cd flink-1.2.0
      • now run – ./bin/flink run examples/streaming/SocketWindowWordCount.jar –port 9000
      • Output –
      • exIhw