a concurrent issue found in TreeCache.class,explanation along with co…

[leyoliu1987]

here sleep a shot time to ensure  invoking method "publishEvent"  after all other eventType case,

because I found more event such as NODE_ADD received again after I have received INITIALLIZED eventType when I restart my Application in my own Linsener which implements the interface TreeCacheListener,so,I believe a concurrent issue occurs, I guess attitional code execution delayed the invoke method "publishEvent" in CASE GET_DATA.

[dragonsinth]

hi leyoliu,

Thank you for contribution.

There are many tests about order of events on startup. For example: TestTreeCache.testStartup()

Are you able to write a test to show the failure you see?

Thank you, Scott

[leyoliu1987]

Hi Mr Scott, Thank you for reply me! I test my appliation many times again, below is my simple code and running result and zookeeper Node structure.

zk node structure: TOPIC LISTENERIPS:192.168.58.22 SENDCHANNEL SMS:true WECHAT:false WEBSOCKET:dragnet SERVERNAME:test TOPICNAME:dragnet

public class TopicTreeListener implements TreeCacheListener {

@Override
public void childEvent(CuratorFramework client, TreeCacheEvent event) throws Exception {
	ChildData data = event.getData();
	Type type = event.getType();
	System.out.println("type="+type);
    }

}

below is my running result:

type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED type=INITIALIZED type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED

[leyoliu1987]

Hi Mr Scott, I'm waiting your reply

[leyoliu1987]

Hi Mr Scott, Thank you for reply me! I test my appliation many times again, below is my simple code and running result and zookeeper Node structure.

zk node structure: TOPIC LISTENERIPS:192.168.58.22 SENDCHANNEL SMS:true WECHAT:false WEBSOCKET:dragnet SERVERNAME:test TOPICNAME:dragnet

public class TopicTreeListener implements TreeCacheListener {

@Override public void childEvent(CuratorFramework client, TreeCacheEvent event) throws Exception { ChildData data = event.getData(); Type type = event.getType(); System.out.println("type="+type); } }

below is my running result:

type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED type=INITIALIZED type=NODE_ADDED type=NODE_ADDED type=NODE_ADDED

https://user-images.githubusercontent.com/32660478/34071705-4276f034-e2b5-11e7-966c-d69d153211ed.png

[dragonsinth]

Hi @leyoliu1987 I tried but I cannot reproduce your problem.

I added a new example, https://github.com/apache/curator/blob/master/curator-examples/src/main/java/cache/TreeCacheExample.java

When I run TreeCacheExample, I do not your problem. I see INITIALIZED happen at the very end after all NODE_ADDED events.

[leyoliu1987]

Hi Mr Scott, I absolutely aggree you are right when you use "cache.getListenable().addListener(T listener)",can you try more time by using "cache.getListenable().addListener(T listener, Executor executor)" like below:

public class TreeCacheExample { public static void main(String[] args) throws Exception { CuratorFramework client = CreateClientExamples.createSimple("127.0.0.1:2181"); client.getUnhandledErrorListenable().addListener((message, e) -> { System.err.println("error=" + message); e.printStackTrace(); }); client.getConnectionStateListenable().addListener((c, newState) -> { System.out.println("state=" + newState); }); client.start();

    TreeCache cache = TreeCache.newBuilder(client, "/").setCacheData(false).build();
     **ExecutorService pool = Executors.newFixedThreadPool(10);**
    cache.getListenable().addListener((c, event) -> {
        if ( event.getData() != null )
        {
            System.out.println("type=" + event.getType() + " path=" + event.getData().getPath());
        }
        else
        {
            System.out.println("type=" + event.getType());
        }
    },**pool** );
    cache.start();

    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    in.readLine();
}

}

[leyoliu1987]

if use " ExecutorService pool = Executors..newCachedThreadPool()" as ThreadPool is no problem. I don't know why .

[dragonsinth]

Hi @leyoliu1987,

I think the executor is your problem. If you use Executors.newFixedThreadPool(10) you are creating 10 different threads to handle events on. When numerous events fire at close to the same time, you will handle all of those events concurrently. That makes you will observe them simultaneously / concurrently / out of order / in a racy way. So this is not a TreeCache problem. If you use a single-threaded executor you should see everything in sequential order.

Thanks! Scott

[abxworld]

I encountered the same problem,although no add new node!

[tisonkun]

Closed as inactive. Also TreeCache is deprecated in favor of CuratorCache.