Saturday, July 25, 2015

Query Storm Data Streams using Esper

As you might already be aware and as documented on the web, “Esper is a component for complex event processing (CEP) which enables rapid development of applications that process large volumes of incoming messages or events, regardless of whether incoming messages are historical or real-time in nature.” Since integration of Storm and Esper was visibly very beneficial for complex processing of tuples incoming in the real-time stream in Storm Bolts, a specialized bolt called the “Esper Bolt” is available.

Esper Bolt enables you to run SQL like queries on your real-time data in storm. Since Esper Bolt is already available, you would not need to write a bolt as described above, but only use it while defining the main Topology class. Below is an illustration of the Topology with a SampleSpout emitting tuples containing 3 fields, namely "deviceId", "deviceTemp" and "time". These field names are listed in the Spout class in a method called declareOutputFields() as below:

@Override
public void declareOutputFields(OutputFieldsDeclarer declarer) {
declarer.declare(new Fields("deviceId", "deviceTemp", "time"));
}                                                                                                                                                                                                                                           

This method is one of the methods to be overridden in both spouts and bolts, which declares names of all the fields that would be emitted per tuple.

Moving forward with the Topology definition, below is the Esper Bolt declaring a statement (query) that runs over every tuple in the incoming stream and emits "deviceId" (id of the device) and "deviceTemp” (temperature of the device)  if the value of the incoming tuple field “deviceTemp” lies between 2000.00 and 3000.00

{
TopologyBuilder builder = new TopologyBuilder();

// add the spout
builder.setSpout("deviceDataAbsorber", new SampleSpout(), 1);

        // define the Esper bolt
EsperBolt deviceTrackerBolt = new EsperBolt.Builder()
.inputs().aliasComponent("deviceDataAbsorber").withFields("deviceId", "deviceTemp", "time").ofTypes(String.class, Float.class, String.class).toEventType("Evaluate")
.outputs().onDefaultStream().emit("deviceId", "deviceTemp")
.statements().add("select evaluate.deviceId as deviceId, evaluate.deviceTemp as deviceTemp from Evaluate.win:time_batch(1 sec) as evaluate where evaluate.deviceTemp <= 3000.00f and evaluate.deviceTemp >= 2000.00f")
.build();
}

The topology can have any number of Esper Bolts or user-defined bolts feeding upon the output of the Esper Bolt. You can define similar query statements depending upon your problem statement.

Hope it helped!

10 comments:

  1. This blog is the general information for the feature. You got a good work for these blog.We have a developing our creative content of this mind.Thank you for this blog. This for very interesting and useful.

    rpa Training in Chennai

    rpa Training in bangalore

    rpa Training in pune

    blueprism Training in Chennai

    blueprism Training in bangalore

    blueprism Training in pune

    iot-training-in-chennai

    ReplyDelete
  2. It is amazing and wonderful to visit your site.Thanks for sharing this information,this is useful to me...

    java training in chennai | java training in bangalore

    java online training | java training in pune

    ReplyDelete
  3. Thanks for taking the time to discuss this, I feel strongly about it and love learning more on this topic.
    python training in rajajinagar
    Python training in btm
    Python training in usa

    ReplyDelete
  4. Good Post! Thank you so much for sharing this pretty post, it was so good to read and useful to improve my knowledge as updated one, keep blogging.
    Devops training in sholinganallur

    ReplyDelete
  5. Awesome..You have clearly explained …Its very useful for me to know about new things..Keep on blogging..

    Blueprism training in Chennai

    Blueprism training in Bangalore

    ReplyDelete
  6. Awesome! Education is the extreme motivation that open the new doors of data and material. So we always need to study around the things and the new part of educations with that we are not mindful.
    angularjs Training in bangalore

    angularjs Training in btm

    angularjs Training in electronic-city

    angularjs online Training

    angularjs Training in marathahalli

    ReplyDelete
  7. Howdy, would you mind letting me know which web host you’re utilizing? I’ve loaded your blog in 3 completely different web browsers, and I must say this blog loads a lot quicker than most. Can you suggest a good internet hosting provider at a reasonable price?
    Amazon Web Services Training in OMR , Chennai | Best AWS Training in OMR,Chennai


    Amazon Web Services Training in Tambaram, Chennai|Best AWS Training in Tambaram, Chennai

    ReplyDelete