Convert Storm - wordCount topology to use a Kafka Spout

Question

I'm new to Storm and Kafka, and I could manage to install both on a local virtual machine after some time. I currently have a working wordCount topology taking sentences from a dropBox text file:

public void nextTuple() {


 final String APP_KEY = "XXXX";
final String APP_SECRET = "XXXX";
DbxAppInfo appInfo = new DbxAppInfo(APP_KEY, APP_SECRET);
DbxRequestConfig config = new DbxRequestConfig("StormTopology/1.0", Locale.getDefault().toString());
String accessToken = "XXXXXXXX";
DbxClient client = new DbxClient(config, accessToken);
String sentence="";
try {FileOutputStream outputStream = new FileOutputStream("fromSpout.txt"); 
try {
    //client.delete("/*.txt");
   DbxEntry.File downloadedFile = client.getFile("/spout.txt", null,outputStream);

   sentence= readFile("fromSpout.txt");          
   if (sentence==null || sentence == "" || sentence == " " || sentence == "/t") {
           Utils.sleep(1000);
           return;
           }                    
        } 
catch (DbxException ex) {  } 
catch (IOException ex) { }       
        //return 1;
finally {
      outputStream.close();
         }
    }
catch (FileNotFoundException ex){}
catch (IOException ex) {}       


if (sentence.length()<2) {  Utils.sleep(10000);  return; }
try { client.delete("/spout.txt");}
 catch (DbxException ex) {  } 
_collector.emit(new Values(sentence)); 
Utils.sleep(1000);      

Now I want to upgrade my spout to use text from Kafka in order to submit to my next bolt in the topology. I tried to follow many articles and codes in git without any success. For example: this kafka spout. Could anyone please help and give me some direction in order to implement the new spout.java file? Thank you!

Answer 1

From storm 0.9.2 release, there is an external storm-kafka package which can do this. Actually this package is contributed back to storm community from storm-kafka-0.8-plus. And there is a test project showing its usage.

In details, first add dependency to your maven (or lein/gradle):

groupId: org.apache.storm
artifactId: storm-kafka
version: 0.9.2-incubating

Then create topology and spout like this:

import storm.kafka

TridentTopology topology = new TridentTopology();
BrokerHosts zk = new ZkHosts("localhost");
TridentKafkaConfig spoutConf = new TridentKafkaConfig(zk, "test-topic");
spoutConf.scheme = new SchemeAsMultiScheme(new StringScheme());
OpaqueTridentKafkaSpout spout = new OpaqueTridentKafkaSpout(spoutConf);