Vertx and couchdb

[EclipseTalk]

Hello,

I using the change apis to get couchdb document update as follow:



// feed type continuous
changes = dbClient.changes().includeDocs(true) .since('546').heartBeat(30000).continuousChanges();
 
// live access to continuous feeds
while (changes.hasNext()) { 
  ChangesResult.Row feed = changes.next();
  
  String docId = feed.getId()
  com.google.gson.JsonObject doc = feed.getDoc()
  String seq = feed.getSeq()
  Gson gson = new Gson()
  String json = gson.toJson(doc);
  System.out.println(json);
  System.out.println("Event docId : " + docId + " - Sequence: " + seq)
  System.out.println("Event Json doc: " + json)

// Send event to the Vertx event bus....

}

I would like to send an event to the eventbus from the while loop above upon new documents changes and have a consumer verticle handle events from the event bus and respond. 

Where should I create the Vertx instance? Is there any sample code to get me started?

Any help is appreciated.

Thanks

[Jez P]

Is this code non-blocking or blocking? If you deploy it within a verticle then, while you may need to wrap in executeBlocking, the verticle already has a reference to the vertx instance. If not in a verticle, then pass the vertx instance in. You'll need to create a vertx instance somewhere for access to the event bus (and on the other side for listeners).

Is this a distributed application or all in one JVM? Are you already deploying verticles? You'll need to tell us a bit more if you want more suggestions than what I've made above. 

[EclipseTalk]

Thanks for the reply, this is blocking code. I do something like:

Invoke the verticle in a clustered vertx as:

Vertx.clusteredVertx(options,  { res ->
  if (res.succeeded()) {
 def vertx = res.result()
 def eventBus = vertx.eventBus()
 System.out.println("We now have a Vert.x instance as clustered")
 
 getFeedFromCouchDb(vertx, eventBus)

 
  } else {
 System.out.println("Failed: " + res.cause());
  }
 })

static private void getFeedFromCouchDb(vertx, eventBus) {
........

// live access to continuous feeds
 while (changes.hasNext()) {
  ChangesResult.Row feed = changes.next();

 
  com.google.gson.JsonObject doc = feed.getDoc()

  Gson gson = new Gson()
  String json = gson.toJson(doc)

  JsonObject eventDoc = new JsonObject(json)
 
  // Run vertx in blocking mode
  vertx.executeBlocking( { future ->
 
  eventBus.publish("feed", eventDoc);
  System.out.println("Publish event message sent address 'couchdb.feed': " + eventDoc.encodePrettily())
 
  future.complete(result);
  },  { res ->
  if (res.succeeded()) {
  System.out.println("Success: "+ res.result());
  }
  });
 
}

The problem is that the eventloop thread will block eventually. How can I listen to the couchdb continuous feed without blocking the event loop?

WARNING: Thread Thread[vert.x-eventloop-thread-0,5,main] has been blocked for 9470 ms, time limit is 2000

Thanks for the help

[Thomas SEGISMONT]

For that kind of use cases, I would schedule a task on a plain old Java executor service and send messages on the event bus from there. The event bus class is thread safe and you can send from any thread (including non Vert.x threads).

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