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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: Multiple consumers on a single server - strange behavior.
Date Sun, 17 Nov 2013 21:57:37 GMT
I was looking at QueueProducer:

 // We register to the listener for monitoring the number of elements
        // in the queue
        framework.getCuratorListenable().addListener(new CuratorListener() {
            @Override
            public void eventReceived(final CuratorFramework framework_,
                    CuratorEvent event) throws Exception {
                if (event.getPath() != null    && event.getPath().equals(Utils.CRAWL_QUEUE_PATH))
{
                    // this also restores the notification
                    List<String> children = framework_.getChildren()
                            .watched().forPath(Utils.CRAWL_QUEUE_PATH);
                    if (children.size() <= QUEUE_SIZE/2) {
                        addQueueContent(QUEUE_SIZE - children.size());
                    }
                }
            }
        });

On Nov 17, 2013, at 1:53 PM, Sznajder ForMailingList <bs4mailinglist@gmail.com> wrote:

> Hi Jordan,
> 
> Thanks again for your so quick answer.
> 
> I would like to be sure about your hint.
> 
> Do you mean that I should change the following method
> 
>             @Override
>             public void consumeMessage(CrawlUrl url) throws Exception {
>                 try {
>                     LOG.info(dateFormat.format(new Date(System.currentTimeMillis()))
+ "["+id+ "-" + MyQueueConsumer.this.name+ "] processed " + url.url);
>                     MyQueueConsumer.this.numberOfProcessedURL++;
>                 } catch (Exception e) {
>                     LOG.error( "["+id+ "-" + MyQueueConsumer.this.name+ "]" + e.getMessage()
+ " for url " + url.url );
>                 } 
>             }
> 
> 
> 
> or the code in the QueueProducer?
> 
> In this last case (code in the QueueProducer), I think it will not solve the problem:
I can see in my logs that the consumers are idle even when the Producer does not do anything...
> 
> Best regards
> 
> Benjamin
> 
> 
> 
> 
> On Sun, Nov 17, 2013 at 11:33 PM, Jordan Zimmerman <jordan@jordanzimmerman.com>
wrote:
> I’ll look further at this, but the first thing that I notice is that you are doing
“work” in your Curator Listener. Please read Curator Tech Note 1:
> 
> 	https://cwiki.apache.org/confluence/display/CURATOR/TN1
> 
> The quickest fix would be to do the getChildren() as a background operation. Alternatively,
you can pass in a thread pool when registering the listener.
> 
> -Jordan
> 
> On Nov 17, 2013, at 1:20 PM, Sznajder ForMailingList <bs4mailinglist@gmail.com>
wrote:
> 
>> First at all , thank you for your answer.
>> 
>> Here is the simple code, I used:
>> 
>> The producer and queueconsummer are given in the class 
>> 
>> Every 5 minutes, I am printing the the number of processed items, and I see some
drastic differences between the different consumers:
>> 
>> 
>> 
>> Producer:
>> =-=-=-=-=
>> 
>> package com.zk;
>> 
>> import java.io.Closeable;
>> import java.io.IOException;
>> import java.text.DateFormat;
>> import java.text.SimpleDateFormat;
>> import java.util.Date;
>> import java.util.List;
>> 
>> import org.apache.curator.framework.CuratorFramework;
>> import org.apache.curator.framework.api.CuratorEvent;
>> import org.apache.curator.framework.api.CuratorListener;
>> import org.apache.curator.framework.recipes.queue.DistributedQueue;
>> import org.apache.curator.test.TestingServer;
>> import org.slf4j.Logger;
>> import org.slf4j.LoggerFactory;
>> 
>> 
>> public class QueueProducer implements Closeable {
>>     
>>     final static Logger LOG = LoggerFactory.getLogger(QueueProducer.class);
>>     
>>     final static DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
>>     
>>     protected static final String PATH = "/test_queue";
>> 
>>     protected static final String LOCK_PATH = "/test_lock_queue";
>>     
>>     private DistributedQueue<CrawlUrl> queue;
>>     
>>     private static final int QUEUE_SIZE = 100000;
>>     
>>     private int items;
>> 
>>     public QueueProducer(CuratorFramework framework) throws Exception {
>>         LOG.info(java.net.InetAddress.getLocalHost().getHostName() + " is a QueueProducer");
>>         System.out.println(java.net.InetAddress.getLocalHost().getHostName() + "
is a QueueProducer");
>>         this.queue = Utils.newDistributedQueue(framework,
>>                 Utils.CRAWL_QUEUE_PATH, Utils.CRAWL_QUEUE_LOCK_PATH, null);
>>         this.queue.start();
>>         addQueueContent(QUEUE_SIZE);
>>         System.out.println("Done with the initial init");
>> 
>> 
>>         // We register to the listener for monitoring the number of elements
>>         // in the queue
>>         framework.getCuratorListenable().addListener(new CuratorListener() {
>>             @Override
>>             public void eventReceived(final CuratorFramework framework_,
>>                     CuratorEvent event) throws Exception {
>>                 if (event.getPath() != null    && event.getPath().equals(Utils.CRAWL_QUEUE_PATH))
{
>>                     // this also restores the notification
>>                     List<String> children = framework_.getChildren()
>>                             .watched().forPath(Utils.CRAWL_QUEUE_PATH);
>>                     if (children.size() <= QUEUE_SIZE/2) {
>>                         addQueueContent(QUEUE_SIZE - children.size());
>>                     }
>>                 }
>>             }
>>         });
>> 
>> 
>>         while (true) {
>>             List<String> children = framework.getChildren().watched().forPath(Utils.CRAWL_QUEUE_PATH);
>>             if (children.size() <= QUEUE_SIZE/2) {
>>                 LOG.info(dateFormat.format(new Date()) + " - In the while(true) -
We call for size " + children.size());
>>                 addQueueContent(QUEUE_SIZE - children.size());
>>             }            
>>                 
>>             Thread.sleep(5000);
>> 
>>         }
>>     }
>> 
>>     void addQueueContent(int numberOfItems) {
>>         LOG.info(dateFormat.format(new Date()) + " - addQueueContent " + numberOfItems);
>>         for (int i = 0; i < numberOfItems; i++) {
>>             try {
>>                 CrawlUrl url = new CrawlUrl(""+this.items++);
>>                 this.queue.put(url);
>>             } catch (Exception e) {
>>                 LOG.error ("Caught an error when adding the item " + i + " in the
initQueueContent()");
>>             }
>>         }
>>     }
>>     
>>     public static void main(String[] args) {
>>         CrawlerPropertyFile props;
>>         try {
>>             props = new CrawlerPropertyFile(args[0]);
>> 
>>             final String connectString;
>>             System.out.println("DEBUG = " + Utils.DEBUG);
>>             if (props.useZkTestServer()) {
>>                 System.out.println("Will launch from zkTestServer");
>>                 TestingServer server = new TestingServer();
>>                 connectString = server.getConnectString();
>>             } else {
>>                 connectString = props.getZkServer();
>>             }
>> 
>>             final CuratorFramework framework = Utils.newFramework(connectString);
>>             framework.start();
>> 
>>             @SuppressWarnings("unused")
>>             QueueProducer producer = new QueueProducer(framework);
>>         } catch (Exception e) {
>>             e.printStackTrace();
>>         }
>> 
>>     }
>> 
>>     @Override
>>     public void close() throws IOException {
>>         this.queue.close();
>>     }
>>     
>>     
>> 
>> }
>> 
>> 
>> 
>> 
>> Consumer 
>> =-=-=-=-=-
>> 
>> package com.zk;
>> 
>> import java.io.Closeable;
>> import java.io.File;
>> import java.io.FileWriter;
>> import java.io.IOException;
>> import java.text.DateFormat;
>> import java.text.SimpleDateFormat;
>> import java.util.Date;
>> 
>> import org.apache.curator.framework.CuratorFramework;
>> import org.apache.curator.framework.recipes.queue.DistributedQueue;
>> import org.apache.curator.framework.recipes.queue.QueueConsumer;
>> import org.apache.curator.framework.state.ConnectionState;
>> import org.apache.curator.test.TestingServer;
>> import org.slf4j.Logger;
>> import org.slf4j.LoggerFactory;
>> 
>> 
>> 
>> public class MyQueueConsumer implements Closeable{
>>     
>>     private DistributedQueue<CrawlUrl> queue;
>> 
>>     String name;
>> 
>>     String id;
>> 
>>     FileWriter timeCounter;
>>     
>>     final static Logger LOG = LoggerFactory.getLogger(MyQueueConsumer.class);
>>     
>>     final static DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
>>     
>>     int numberOfProcessedURL;
>> 
>>     private com.zk.MyQueueConsumer.FileWriterThread timeCounterThread;
>>     
>>     private class FileWriterThread extends Thread {
>> 
>>         public FileWriterThread() {
>>             // empty ctor
>>         }
>> 
>>         @Override
>>         public void run() {
>>             // We write the stats:
>> 
>>             try {
>>                 while (true) {
>>                     MyQueueConsumer.this.timeCounter.write(dateFormat.format(new
Date()) + " "+
>>                             "[numberOfProcessed="+MyQueueConsumer.this.numberOfProcessedURL
   +"]\n") ;
>>                     MyQueueConsumer.this.timeCounter.flush();
>>                 
>>                     // Sleeps 5 minutes
>>                     Thread.sleep(300000);
>>                 }
>>             } catch (Exception e) {
>>                 // TODO Auto-generated catch block
>>                 e.printStackTrace();
>>             }
>>         }
>>     }
>>     
>>     
>>     public MyQueueConsumer(CuratorFramework framework, final String id) throws Exception
{
>>         this.id = id;
>>         this.name = java.net.InetAddress.getLocalHost().getHostName();
>>         this.timeCounter = new FileWriter(new File("MyQueueConsumer_"+ this.name
+ "_" +id + "_timeCounter.txt"));
>>         
>> //        this.timeCounterThread = new FileWriterThread();
>> //        this.timeCounterThread.start();
>>         this.queue = Utils.newDistributedQueue(framework, Utils.CRAWL_QUEUE_PATH,
Utils.CRAWL_QUEUE_LOCK_PATH, new QueueConsumer<CrawlUrl>() {
>> 
>>             @Override
>>             public void stateChanged(CuratorFramework client, ConnectionState newState)
{
>>                 System.out.println(String.format("[%s] connection state changed to
%s", id, newState));
>>             }
>> 
>>             @Override
>>             public void consumeMessage(CrawlUrl url) throws Exception {
>>                 try {
>>                     LOG.info(dateFormat.format(new Date(System.currentTimeMillis()))
+ "["+id+ "-" + MyQueueConsumer.this.name+ "] processed " + url.url);
>>                     MyQueueConsumer.this.numberOfProcessedURL++;
>>                 } catch (Exception e) {
>>                     LOG.error( "["+id+ "-" + MyQueueConsumer.this.name+ "]" + e.getMessage()
+ " for url " + url.url );
>>                 } 
>>             }
>> 
>>         });
>>         try {
>>             this.queue.start();
>>         } catch (Exception e) {
>>             e.printStackTrace();
>>         }
>> 
>>     }
>>     
>>     public static void main(String[] args) {
>>         try {
>>             CrawlerPropertyFile props = new CrawlerPropertyFile(args[0]);
>>     
>>             final String connectString;
>>             System.out.println("DEBUG = " + Utils.DEBUG);
>>             if (props.useZkTestServer()) {
>>                 System.out.println("Will launch from zkTestServer");
>>                 TestingServer server = new TestingServer();
>>                 connectString = server.getConnectString();
>>             } else {
>>                 connectString = props.getZkServer();
>>             }
>>     
>>             final CuratorFramework framework = Utils.newFramework(connectString);
>>             framework.start();
>>     
>>             final MyQueueConsumer[] queueConsumers = new MyQueueConsumer[props.getNumberOfWorkers()];
>>     
>>             for (int i = 0; i < queueConsumers.length; i++) {
>>                 queueConsumers[i] = new MyQueueConsumer(framework, "id_"+i);
>>             }
>>     
>>             Runtime.getRuntime().addShutdownHook(new Thread() {
>>                 @Override
>>                 public void run() {
>>                     // close workers
>>                     Throwable t = null;
>>                     LOG.info("We close the workers");
>>                     for (MyQueueConsumer queueConsumer : queueConsumers) {
>>                         try {
>>                             queueConsumer.close();
>>                         } catch (Throwable th) {
>>                             if (t == null) {
>>                                 t = th;
>>                             }
>>                         }
>>                     }
>>                     // throw first exception that we encountered
>>                     if (t != null) {
>>                         throw new RuntimeException("some workers failed to close",
t);
>>                     }
>>                 }
>>             });
>>             
>>         }catch (Exception e ){
>>             e.printStackTrace();
>>         }
>>     }
>> 
>>     @Override
>>     public void close() throws IOException {
>>         this.queue.close();
>>     }
>> }
>> 
>> 
>> 
>> 
>> Main
>> -=-=-
>> 
>> package com.zk;
>> 
>> import org.apache.curator.framework.CuratorFramework;
>> import org.apache.curator.test.TestingServer;
>> 
>> 
>> 
>> public class QueueTestMain {
>> 
>>     /**
>>      * @param args
>>      */
>>     public static void main(String[] args) {
>>         CrawlerPropertyFile props;
>>         try {
>>             props = new CrawlerPropertyFile(args[0]);
>> 
>>             final String connectString;
>>             System.out.println("DEBUG = " + Utils.DEBUG);
>>             if (props.useZkTestServer()) {
>>                 System.out.println("Will launch from zkTestServer");
>>                 TestingServer server = new TestingServer();
>>                 connectString = server.getConnectString();
>>             } else {
>>                 connectString = props.getZkServer();
>>             }
>> 
>>             final CuratorFramework framework = Utils.newFramework(connectString);
>>             framework.start();
>>             
>> 
>>             if (args[1] != null && args[1].equalsIgnoreCase("true")) {
>>                 @SuppressWarnings("unused")
>>                 QueueProducer producer = new QueueProducer(framework);
>>             } else {
>>             
>>                 final MyQueueConsumer[] queueConsumers = new MyQueueConsumer[props.getNumberOfWorkers()];
>>                 
>>                 for (int i = 0; i < queueConsumers.length; i++) {
>>                     queueConsumers[i] = new MyQueueConsumer(framework, "id_"+i);
>>                 }
>>         
>>                 Runtime.getRuntime().addShutdownHook(new Thread() {
>>                     @Override
>>                     public void run() {
>>                         // close workers
>>                         Throwable t = null;
>>                         for (MyQueueConsumer queueConsumer : queueConsumers) {
>>                             try {
>>                                 queueConsumer.close();
>>                             } catch (Throwable th) {
>>                                 if (t == null) {
>>                                     t = th;
>>                                 }
>>                             }
>>                         }
>>                         // throw first exception that we encountered
>>                         if (t != null) {
>>                             throw new RuntimeException("some workers failed to close",
t);
>>                         }
>>                     }
>>                 });
>>     
>>                 
>>             }
>>         }catch (Exception e ){
>>             e.printStackTrace();
>>         }
>> 
>>     }
>> 
>> }
>> 
>> 
>> 
>> 
>> Example of output:
>> 
>> 
>> 
>> 
>> 
>> On Sun, Nov 17, 2013 at 10:14 PM, Jordan Zimmerman <jordan@jordanzimmerman.com>
wrote:
>> Can you produce a test that shows this? Anything else interesting in the log? Of
course, there could be a bug.
>> 
>> -Jordan
>> 
>> On Nov 14, 2013, at 1:18 PM, Sznajder ForMailingList <bs4mailinglist@gmail.com>
wrote:
>> 
>> > Hi
>> >
>> > I made a short test as following:
>> >
>> > - I have a chorum of 3 nodes for Zookeeper.
>> > - I wrote a class using Curator QueueProducer who produces all the time (when
the queue is 10% full, it creates new items) , items (random integer)
>> > - I wrote a simple class using Curator Queue Consumer which simply prints to
Log "consumed item i".
>> >
>> > I tested some different combinations :
>> > - running the consumers on one, two or three nodes.
>> > - running one or more consumers in parallel on a given node.
>> >
>> >
>> > But, and here is my question: I see some very strange behavior when I have several
consummers in parallel on a node. For example, running 5 consumers per node on 3 nodes, I
see a throughput **very** slow. When looking at my Log, I see that most of the consumers are
most of the time on an idle state....
>> >
>> > Do I mistake somewhere?
>> >  I was expecting to enhance the throughput by augmenting the number of consumers,
I am surprised to see the opposite....
>> >
>> > Thanks a lot
>> >
>> > Benjamin
>> 
>> 
> 
> 


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