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https://issues.apache.org/jira/browse/ZOOKEEPER-887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15472910#comment-15472910
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Prabhunath Yadav commented on ZOOKEEPER-887:
--------------------------------------------
Even the solution provided by sanjivsingh is not optimal , the node should be
deleted in sequence that is the lowest one should be deleted first , as it is
following queue property , i have made the optimal and accurate solution for
this and would like to attach the solution.
> Bug at - Producer-Consumer Example
> -----------------------------------
>
> Key: ZOOKEEPER-887
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-887
> Project: ZooKeeper
> Issue Type: Bug
> Components: java client
> Reporter: sanjivsingh
> Priority: Minor
> Attachments: zookeeper-887.patch
>
>
> I tried to test Producer-Consumer Example published at ...
> http://hadoop.apache.org/zookeeper/docs/r3.0.0/zookeeperTutorial.html
> Queue.produce( int p) working correctly,,,
> there is problem in Queue.consume( ) method.
> int consume() throws KeeperException, InterruptedException{
> int retvalue = -1;
> Stat stat = null;
> // Get the first element available
> while (true) {
> synchronized (mutex) {
> List<String> list = zk.getChildren(root, true);
> if (list.size() == 0) {
> System.out.println("Going to wait");
> mutex.wait();
> } else {
> Integer min = new
> Integer(list.get(0).substring(7));
> for(String s : list){
> Integer tempValue = new
> Integer(s.substring(7));
> //System.out.println("Temporary value: " +
> tempValue);
> if(tempValue < min) min = tempValue;
> }
> System.out.println("Temporary value: " + root
> + "/element" + min);
> byte[] b = zk.getData(root + "/element" + min,
> false, stat);
> zk.delete(root + "/element" + min, 0);
> ByteBuffer buffer = ByteBuffer.wrap(b);
> retvalue = buffer.getInt();
> return retvalue;
> }
> }
> }
> }
> wat exactly produce( ) doing is that add child under root like
> element000000001,
> element000000002 ,element000000003 etc....
> but
> In consume( ) method ,
> 1. Integer min = new Integer(list.get(0).substring(7));
> 2. for(String s : list){
> 3. Integer tempValue = new
> Integer(s.substring(7));
> 4. if(tempValue < min) min = tempValue;
> 5. }
> 6. byte[] b = zk.getData(root + "/element" + min,
> false, stat);
> 7. zk.delete(root + "/element" + min, 0);
> bcuz of..
> line 1 & 3 .. converting like String 000000001 --------->
> Interger 1
> and bcuz of this , in line 6 & 7
> It is tring to access znode like at root + "/element1" rather
> than root + "/element000000001"
> that is definelty no-existing one..........
> I m putting forward a solution....
> int consume() throws KeeperException, InterruptedException{
> int retvalue = -1;
> Stat stat = null;
> // Get the first element available
> while (true) {
> synchronized (mutex) {
> List<String> list = zk.getChildren(root, true);
> if (list.size() == 0) {
> System.out.println("Going to wait");
> mutex.wait();
> } else {
> Integer min = new
> Integer(list.get(0).substring(7));
> int i=0 ,p=0;
> for(String s : list){
> Integer tempValue = new
> Integer(s.substring(7));
> if(tempValue < min)
> p=i;
> i++;
> }
> byte[] b = zk.getData(root + "/element" +
> list.get(p).substring(7), false, stat);
> zk.delete(root + "/element" +
> list.get(p).substring(7), 0);
> ByteBuffer buffer = ByteBuffer.wrap(b);
> retvalue = buffer.getInt();
> return retvalue;
> }
> }
> }
> }
> }
>
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