zookeeper-user — Mailing list for users of ZooKeeper

Re: [Zookeeper-user] create() failure

[Avinash L. <avi...@gm...>]

These are sequence of interactions with ZooKeeper:

(1) Instantiate Zookeeper and perform the checks for a bunch of znodes. All
this works as expected.
(2) Spawn a thread which tries to perform leader election. This is where I
am trying to create the znode with the sequence numbers.

I am assuming that the client connected successfully because the checks in
step 1 went through fine. Also I have Zookeeper run in a cluster of 5 nodes
which are all in the same rack and in the same data center. Another question
I have is if I set the seesion timeout parameter to 5000 ms in the ZooKeeper
ctor does that mean my session is invalidated after 5000 ms or is kept alive
after every 5000 ms. What is the significance of the session timeout
parameter?

Thanks
Avinash

On Fri, Jun 6, 2008 at 1:55 AM, Flavio Junqueira <fpj...@ya...>
wrote:

> It could be because your client has not connected properly to a ZooKeeper
> server. Have you taken a look at the logs on the server side to make sure
> that a session has been created? Could you give me a little more detail
> about your setup?
>
> -Flavio
>
>
> ----- Original Message ----
> From: Avinash Lakshman <avi...@gm...>
> To: zoo...@li...
> Sent: Friday, June 6, 2008 10:49:16 AM
> Subject: [Zookeeper-user] create() failure
>
> When I do execute the folloiwing code :
>
> String pathCreated = zk.create(createPath, new byte[0],
> Ids.OPEN_ACL_UNSAFE, (CreateFlags.SEQUENCE  | CreateFlags.EPHEMERAL) );
>
>
> It seems to fail silently w/o reporting any errors. I mean I have a log
> statement after this line which never shows up. However it works if I
> execute it via the debugger. Any ideas as to what might be happening?
>
> Thanks
> A
>
>

Re: [Zookeeper-user] create() failure

[Flavio J. <fpj...@ya...>]

It could be because your client has not connected properly to a ZooKeeper server. Have you taken a look at the logs on the server side to make sure that a session has been created? Could you give me a little more detail about your setup? 

-Flavio


----- Original Message ----
From: Avinash Lakshman <avi...@gm...>
To: zoo...@li...
Sent: Friday, June 6, 2008 10:49:16 AM
Subject: [Zookeeper-user] create() failure

When I do execute the folloiwing code :

String pathCreated = zk.create(createPath, new byte[0], Ids.OPEN_ACL_UNSAFE, (CreateFlags.SEQUENCE  | CreateFlags.EPHEMERAL) ); 


It seems to fail silently w/o reporting any errors. I mean I have a log statement after this line which never shows up. However it works if I execute it via the debugger. Any ideas as to what might be happening?

Thanks
A



      

[Zookeeper-user] create() failure

[Avinash L. <avi...@gm...>]

When I do execute the folloiwing code :

String pathCreated = zk.create(createPath, new byte[0], Ids.OPEN_ACL_UNSAFE,
(CreateFlags.SEQUENCE  | CreateFlags.EPHEMERAL) );


It seems to fail silently w/o reporting any errors. I mean I have a log
statement after this line which never shows up. However it works if I
execute it via the debugger. Any ideas as to what might be happening?

Thanks
A

Re: [Zookeeper-user] Watch event handlers

[Patrick H. <ph...@gm...>]

I entered a bug based on your feedback:
http://sourceforge.net/tracker/index.php?func=detail&aid=1985723&group_id=209147&atid=1008544

Your WatcherImpl process method will be called for both Node events as 
well as State change events. In this case you are probably being called 
for the transition to connected state.

See this example of processing watch events:
http://zookeeper.wiki.sourceforge.net/ZooKeeperJavaExample

Second parameter is session timeout in milliseconds.
See the javadoc for the zookeeper class

  * To create a client(ZooKeeper) object, the application needs to pass 
a string
  * containing a list of host:port pairs, each corresponding to a ZooKeeper
  * server; a sessionTimeout; and an object of Watcher type.


See com.yahoo.zookeeper.Watcher.Event for list of possible state 
transitions (disconnected/expired/etc...).

Patrick

Avinash Lakshman wrote:
> I have the following two of code:
> 
>  ZooKeeper zk = new ZooKeeper("cassandra001.snc1.facebook.com:5001 
> <http://cassandra001.snc1.facebook.com:5001>", 5000, new 
> WatcherImpl());       
>  Stat stat = zk.exists("/", false);
> 
> I set my breakpoint at the second line and I see output from the 
> invocation of the process() implemented in the WatcherImpl class. My 
> question is why is the process() being invoked on creation of the 
> ZooKeeper object? Also what is the purpose of the second parameter in 
> the ZooKeeper ctor? Does it have anything to for failure detection ofthe 
> client connected to the ZooKeeper server?
> 
> Thanks in advance
> Avinash
> 
> 
> On Thu, Jun 5, 2008 at 10:49 AM, Avinash Lakshman 
> <avi...@gm... <mailto:avi...@gm...>> wrote:
> 
>     That would be awesome. This allows IMHO a cleaner design with
>     respect to handling of events. I must add that this is a great piece
>     of software though. Tremendous job in putting this together.
> 
>     Regards
>     A
> 
> 
>     On Thu, Jun 5, 2008 at 8:44 AM, Benjamin Reed <br...@ya...
>     <mailto:br...@ya...>> wrote:
> 
>         As of the latest release the same watcher will be called for all
>         events. The
>         event callback includes the path of the znode that changed,
>         which is how you
>         can distinguish events.
> 
>         In the next major release, we will be allowing a watch object to
>         be passed to
>         the requests to make it easier for programmers to control what
>         is going to be
>         invoked with the watch event arrives.
> 
>         ben
> 
>         On Thursday 05 June 2008 00:15:54 Avinash Lakshman wrote:
>          > Hi All
>          >
>          > I am trying to get my feet wet with Zookeeper. I am trying to
>         set up watch
>          > events for a call to getChildren() for a particular znode. My
>         question is
>          > whether the same watcher that the ZooKeeper instance was
>         constructed with
>          > going to be called for all watch events. If so how do I know
>         for what event
>          > it is being called.
>          >
>          > Thanks
>          > A
> 
> 
> 
> 
> 
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Re: [Zookeeper-user] Watch event handlers

[Avinash L. <avi...@gm...>]

I have the following two of code:

 ZooKeeper zk = new ZooKeeper("cassandra001.snc1.facebook.com:5001", 5000,
new WatcherImpl());
 Stat stat = zk.exists("/", false);

I set my breakpoint at the second line and I see output from the invocation
of the process() implemented in the WatcherImpl class. My question is why is
the process() being invoked on creation of the ZooKeeper object? Also what
is the purpose of the second parameter in the ZooKeeper ctor? Does it have
anything to for failure detection ofthe client connected to the ZooKeeper
server?

Thanks in advance
Avinash


On Thu, Jun 5, 2008 at 10:49 AM, Avinash Lakshman <
avi...@gm...> wrote:

> That would be awesome. This allows IMHO a cleaner design with respect to
> handling of events. I must add that this is a great piece of software
> though. Tremendous job in putting this together.
>
> Regards
> A
>
>
> On Thu, Jun 5, 2008 at 8:44 AM, Benjamin Reed <br...@ya...> wrote:
>
>> As of the latest release the same watcher will be called for all events.
>> The
>> event callback includes the path of the znode that changed, which is how
>> you
>> can distinguish events.
>>
>> In the next major release, we will be allowing a watch object to be passed
>> to
>> the requests to make it easier for programmers to control what is going to
>> be
>> invoked with the watch event arrives.
>>
>> ben
>>
>> On Thursday 05 June 2008 00:15:54 Avinash Lakshman wrote:
>> > Hi All
>> >
>> > I am trying to get my feet wet with Zookeeper. I am trying to set up
>> watch
>> > events for a call to getChildren() for a particular znode. My question
>> is
>> > whether the same watcher that the ZooKeeper instance was constructed
>> with
>> > going to be called for all watch events. If so how do I know for what
>> event
>> > it is being called.
>> >
>> > Thanks
>> > A
>>
>>
>>
>

Re: [Zookeeper-user] Watch event handlers

[Avinash L. <avi...@gm...>]

That would be awesome. This allows IMHO a cleaner design with respect to
handling of events. I must add that this is a great piece of software
though. Tremendous job in putting this together.

Regards
A

On Thu, Jun 5, 2008 at 8:44 AM, Benjamin Reed <br...@ya...> wrote:

> As of the latest release the same watcher will be called for all events.
> The
> event callback includes the path of the znode that changed, which is how
> you
> can distinguish events.
>
> In the next major release, we will be allowing a watch object to be passed
> to
> the requests to make it easier for programmers to control what is going to
> be
> invoked with the watch event arrives.
>
> ben
>
> On Thursday 05 June 2008 00:15:54 Avinash Lakshman wrote:
> > Hi All
> >
> > I am trying to get my feet wet with Zookeeper. I am trying to set up
> watch
> > events for a call to getChildren() for a particular znode. My question is
> > whether the same watcher that the ZooKeeper instance was constructed with
> > going to be called for all watch events. If so how do I know for what
> event
> > it is being called.
> >
> > Thanks
> > A
>
>
>

Re: [Zookeeper-user] Watch event handlers

[Benjamin R. <br...@ya...>]

As of the latest release the same watcher will be called for all events. The 
event callback includes the path of the znode that changed, which is how you 
can distinguish events.

In the next major release, we will be allowing a watch object to be passed to 
the requests to make it easier for programmers to control what is going to be 
invoked with the watch event arrives.

ben

On Thursday 05 June 2008 00:15:54 Avinash Lakshman wrote:
> Hi All
>
> I am trying to get my feet wet with Zookeeper. I am trying to set up watch
> events for a call to getChildren() for a particular znode. My question is
> whether the same watcher that the ZooKeeper instance was constructed with
> going to be called for all watch events. If so how do I know for what event
> it is being called.
>
> Thanks
> A

Re: [Zookeeper-user] Stat attributes - what do they mean?

[Benjamin R. <br...@ya...>]

I've updated the wiki page to document these members: 

http://zookeeper.wiki.sourceforge.net/ZooKeeperDataModel

From the wiki:

    *  czxid - The zxid of the change that caused this znode to be created.
    * mzxid - The zxid of the change that last modified this znode.
    * ctime - The time in milliseconds from epoch when this znode was created.
    * mtime - The time in milliseconds from epoch when this znode was last 
modified.
    * version - The number of changes to the data of this znode.
    * cversion - The number of changes to the children of this znode.
    * aversion - The number of changes to the ACL of this znode.
    * ephemeralOwner - The session id of the owner of this znode if the znode 
is an ephemeral node. If it is not an ephemeral node, it will be zero.

ben

On Wednesday 04 June 2008 16:43:25 Shane Mingins wrote:
> Hi
>
> I am looking for some docs (if they exist) otherwise info on the
> attributes in the generated Stat class
>
>    private long czxid;
>    private long mzxid;
>    private long ctime;
>    private long mtime;
>    private int version;
>    private int cversion;
>    private int aversion;
>    private long ephemeralOwner;
>
> I cannot determine what exactly each are.
>
> Thanks
> Shane
>
>
>
> Shane Mingins
> ELC Technologies (TM)
> 1921 State Street
> Santa Barbara, CA 93101
>
>
> Phone: +64 4 568 6684
> Mobile: +64 21 435 586
> Email:  smi...@el...
> AIM:     ShaneMingins
> Skype: shane.mingins
>
> (866) 863-7365 Tel - Santa Barbara Office
> (866) 893-1902 Fax - Santa Barbara Office
>
> +44 020 7504 1346 Tel - London Office
> +44 020 7504 1347 Fax - London Office
>
> http://www.elctech.com
>
> --------------------------------------------------------------------
> Privacy and Confidentiality Notice:
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> for the named recipient(s) only. It may contain privileged and
> confidential information. If you are not an intended recipient, you
> must not copy, forward, distribute or take any action in reliance on
> it. If you have received this electronic mail message in
>
>
> -------------------------------------------------------------------------
> Check out the new SourceForge.net Marketplace.
> It's the best place to buy or sell services for
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Re: [Zookeeper-user] Watch event handlers

[Flavio J. <fpj...@ya...>]

Avinash, When you create a ZooKeeper object, you have to pass an object that implements the Watcher interface. This interface basically defines a method "process(WatcherEvent)" that your object has to implement. Unless you change it with the method "ZooKeeper.register(Watcher w)", a call back due to a watch event is an invocation to the "process()" method of the initial object. 

The process() method receives a parameter of type WatcherEvent, which has three fields: type, state, and path. Please take a look at Watcher.java for types and states. I think the path field is obvious. Let me know if you have any trouble figuring this out.

Also, I know that there is information missing there, but please consider taking a look at our wiki page:

http://zookeeper.wiki.sourceforge.net/ZooKeeperWatches

and let us know if you have comments on how to improve it.

Thanks,
-Flavio


----- Original Message ----
From: Avinash Lakshman <avi...@gm...>
To: zoo...@li...
Sent: Thursday, June 5, 2008 9:15:54 AM
Subject: [Zookeeper-user] Watch event handlers

Hi All

I am trying to get my feet wet with Zookeeper. I am
trying to set up watch events for a call to getChildren() for a
particular znode. My question is whether the same watcher that the
ZooKeeper instance was constructed with going to be called for all
watch events. If so how do I know for what event it is being called.

Thanks
A 


      

[Zookeeper-user] Watch event handlers

[Avinash L. <avi...@gm...>]

Hi All

I am trying to get my feet wet with Zookeeper. I am trying to set up watch
events for a call to getChildren() for a particular znode. My question is
whether the same watcher that the ZooKeeper instance was constructed with
going to be called for all watch events. If so how do I know for what event
it is being called.

Thanks
A

Re: [Zookeeper-user] Stat attributes - what do they mean?

[Patrick H. <ph...@gm...>]

Seems we don't have documentation for this, I looked in both the api 
docs and the wiki. I have created a bug for us to add this:
https://sourceforge.net/tracker/index.php?func=detail&aid=1984955&group_id=209147&atid=1008544

in the mean time:
>    private long czxid;
created zxid
>    private long mzxid;
last modified zxid
>    private long ctime;
created time
>    private long mtime;
last modified time
>    private int version;
current version
>    private int cversion;
child list version
>    private int aversion;
acl list version
>    private long ephemeralOwner;
client id of the owner (if this is ephemeral node, 0 otw)

zxid is the transaction id
times are in milliseconds (java System.currentTimeMillis())
version is incremented on each change (initalized to 0)

Regards,

Patrick

> 
> 
> Shane Mingins
> ELC Technologies (TM)
> 1921 State Street
> Santa Barbara, CA 93101
> 
> 
> Phone: +64 4 568 6684
> Mobile: +64 21 435 586
> Email:  smi...@el...
> AIM:     ShaneMingins
> Skype: shane.mingins
> 
> (866) 863-7365 Tel - Santa Barbara Office
> (866) 893-1902 Fax - Santa Barbara Office
> 
> +44 020 7504 1346 Tel - London Office
> +44 020 7504 1347 Fax - London Office
> 
> http://www.elctech.com
> 
> --------------------------------------------------------------------
> Privacy and Confidentiality Notice:
> The information contained in this electronic mail message is intended  
> for the named recipient(s) only. It may contain privileged and  
> confidential information. If you are not an intended recipient, you  
> must not copy, forward, distribute or take any action in reliance on  
> it. If you have received this electronic mail message in
> 
> 
> -------------------------------------------------------------------------
> Check out the new SourceForge.net Marketplace.
> It's the best place to buy or sell services for
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> _______________________________________________
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> Zoo...@li...
> https://lists.sourceforge.net/lists/listinfo/zookeeper-user

[Zookeeper-user] Stat attributes - what do they mean?

[Shane M. <smi...@el...>]

Hi

I am looking for some docs (if they exist) otherwise info on the  
attributes in the generated Stat class

   private long czxid;
   private long mzxid;
   private long ctime;
   private long mtime;
   private int version;
   private int cversion;
   private int aversion;
   private long ephemeralOwner;

I cannot determine what exactly each are.

Thanks
Shane



Shane Mingins
ELC Technologies (TM)
1921 State Street
Santa Barbara, CA 93101


Phone: +64 4 568 6684
Mobile: +64 21 435 586
Email:  smi...@el...
AIM:     ShaneMingins
Skype: shane.mingins

(866) 863-7365 Tel - Santa Barbara Office
(866) 893-1902 Fax - Santa Barbara Office

+44 020 7504 1346 Tel - London Office
+44 020 7504 1347 Fax - London Office

http://www.elctech.com

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Privacy and Confidentiality Notice:
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it. If you have received this electronic mail message in

[Zookeeper-user] test

[Haijun C. <ha...@ki...>]

test

Re: [Zookeeper-user] Connection States - two constants set to zero

[Patrick H. <ph...@gm...>]

That does seem unusual - I entered a bug and assigned to Ben for feedback.

http://sourceforge.net/tracker/index.php?func=detail&aid=1979772&group_id=209147&atid=1008544

Thanks,

Patrick

Shane Mingins wrote:
> Hi
> 
> I was looking through the source code and I was just wondering about  
> the connection states defined in Watcher ....
> 
>          final public static int KeeperStateChanged = 0;
> 
>          final public static int KeeperStateUnknown = -1;
> 
>          final public static int KeeperStateDisconnected = 0;
> 
>          final public static int KeeperStateNoSyncConnected = 1;
> 
>          final public static int KeeperStateSyncConnected = 3;
> 
>          public static final int KeeperStateExpired = -112;
> 
> 
> And why there are too constants set to 0?  I could not find a usage  
> for the constant KeeperStateChanged just quickly using the find usage  
> option in IntelliJ.
> 
> It's been a while since I have been actively doing any Java dev so  
> maybe I am just missing the obvious?  I am developing a JRuby api for  
> ZooKeeper and was just logging the states from events in a watcher  
> when I came across this.
> 
> Thanks
> Shane
> 
> 
> 
> -------------------------------------------------------------------------
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> Defy all challenges. Microsoft(R) Visual Studio 2008.
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[Zookeeper-user] Does ZooKeeper includes Paxos ?

[Chen Z. <cz...@gm...>]

Hello,

I was wondering whether ZooKeeper includes Paxos in its code. Can you tell
me which part of the code is about the Paxos? Maybe ZooKeeper may provide a
good chance for people to see how to implement Paxos correctly and
efficiently.
Thank you.

[Zookeeper-user] Connection States - two constants set to zero

[Shane M. <smi...@el...>]

Hi

I was looking through the source code and I was just wondering about  
the connection states defined in Watcher ....

         final public static int KeeperStateChanged = 0;

         final public static int KeeperStateUnknown = -1;

         final public static int KeeperStateDisconnected = 0;

         final public static int KeeperStateNoSyncConnected = 1;

         final public static int KeeperStateSyncConnected = 3;

         public static final int KeeperStateExpired = -112;


And why there are too constants set to 0?  I could not find a usage  
for the constant KeeperStateChanged just quickly using the find usage  
option in IntelliJ.

It's been a while since I have been actively doing any Java dev so  
maybe I am just missing the obvious?  I am developing a JRuby api for  
ZooKeeper and was just logging the states from events in a watcher  
when I came across this.

Thanks
Shane

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Juan R. <Jua...@Su...>]

Benjamin Reed wrote:
> It is supported. We run a lot of unit tests that way. Is it possible that the 
> machine is simply getting overloaded. (Especially with respect to disk 
> activity?) You have a rather large timeout, so the machine would really need 
> to be getting swamped.

Hi, Ben.  I'd be very surprised if the machine is getting swamped.  I 
verified this and mpstat shows 98% idle time on both CPUs in the 
machine.  Running the iotop DTrace script shows only two processes 
making disk access within each sampling interval, one of them being 
ZooKeeper.  The disk access time is at most 30ms for ZooKeeper, same for 
the other processes, which computes to 0% (very low) disk utilization 
for each sampling interval.

I will try to debug the single-machine case further if I get a chance. 
I started there because I thought it would be the quickest way to try 
ZooKeeper out.  Turns out deploying it in clustered mode onto 5 virtual 
hosts got me there quicker.  I see no problems in that scenario.

To provide a bit of context, I was working on a locking/leader election 
service for use by applications needing such a service on our research 
cloud computing platform (https://wwww.projectcaroline.net).  Someone in 
the team pointed me to ZooKeeper and rather than reinvent the wheel, I 
am trying to see if we can use ZooKeeper "out-of-the-box".  So far it 
seems to fit the bill.  Given none of the deployment scenarios we have 
involve client and service on the same host (in fact, such a deployment 
is not possible in our platform), the exceptions I see when running 
client and service on the same machine are not an impediment.  I am 
curious about them, so I will probably investigate further as time permits.

Thanks again for your help.

Regards,

Juan


> 
> ben
> 
> On Friday 23 May 2008 13:00:02 Juan Ramirez wrote:
>> A piece of info I left out which appears to be relevant is that I was
>> running the standalone server and its client on the same machine.
>> Perhaps this is not supported?  I am not seeing the problem in a
>> clustered deployment with 5 zookeeper instances.
>>
>> Thanks,
>>
>> Juan
>>
>> Juan Ramirez wrote:
>>> Mahadev Konar wrote:
>>>> Hi Juan,
>>>>   Can you tell us what you are doing in your client code and when you
>>>> see this problem?
>>> Hi, Mahadev.  It seems to happen when attempting to create a new node.
>>> Might be a timing issue because it does not happen all the time.  The
>>> client code where this happens is quite simple:
>>>
>>>      if (keeper.exists(path, false) == null) {
>>>          file = keeper.create(path, "hello".getBytes(),
>>>              ZooDefs.Ids.OPEN_ACL_UNSAFE, flags);
>>>
>>>  >You are running with a standalone zookeeper server
>>>> right?
>>> Correct.
>>>
>>> Thanks,
>>>
>>> Juan
>>>
>>>
>>> -------------------------------------------------------------------------
>>> This SF.net email is sponsored by: Microsoft
>>> Defy all challenges. Microsoft(R) Visual Studio 2008.
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>>> _______________________________________________
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>>> Zoo...@li...
>>> https://lists.sourceforge.net/lists/listinfo/zookeeper-user
>> -------------------------------------------------------------------------
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>> Defy all challenges. Microsoft(R) Visual Studio 2008.
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>> _______________________________________________
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>> Zoo...@li...
>> https://lists.sourceforge.net/lists/listinfo/zookeeper-user
> 
> 

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Benjamin R. <br...@ya...>]

It is supported. We run a lot of unit tests that way. Is it possible that the 
machine is simply getting overloaded. (Especially with respect to disk 
activity?) You have a rather large timeout, so the machine would really need 
to be getting swamped.

ben

On Friday 23 May 2008 13:00:02 Juan Ramirez wrote:
> A piece of info I left out which appears to be relevant is that I was
> running the standalone server and its client on the same machine.
> Perhaps this is not supported?  I am not seeing the problem in a
> clustered deployment with 5 zookeeper instances.
>
> Thanks,
>
> Juan
>
> Juan Ramirez wrote:
> > Mahadev Konar wrote:
> >> Hi Juan,
> >>   Can you tell us what you are doing in your client code and when you
> >> see this problem?
> >
> > Hi, Mahadev.  It seems to happen when attempting to create a new node.
> > Might be a timing issue because it does not happen all the time.  The
> > client code where this happens is quite simple:
> >
> >      if (keeper.exists(path, false) == null) {
> >          file = keeper.create(path, "hello".getBytes(),
> >              ZooDefs.Ids.OPEN_ACL_UNSAFE, flags);
> >
> >  >You are running with a standalone zookeeper server
> >>
> >> right?
> >
> > Correct.
> >
> > Thanks,
> >
> > Juan
> >
> >
> > -------------------------------------------------------------------------
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> > Defy all challenges. Microsoft(R) Visual Studio 2008.
> > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
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> > Zoo...@li...
> > https://lists.sourceforge.net/lists/listinfo/zookeeper-user
>
> -------------------------------------------------------------------------
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Re: [Zookeeper-user] odd exceptions when using zookeeper

[Juan R. <Jua...@Su...>]

A piece of info I left out which appears to be relevant is that I was 
running the standalone server and its client on the same machine. 
Perhaps this is not supported?  I am not seeing the problem in a 
clustered deployment with 5 zookeeper instances.

Thanks,

Juan

Juan Ramirez wrote:
> Mahadev Konar wrote:
>> Hi Juan,
>>   Can you tell us what you are doing in your client code and when you
>> see this problem?
> 
> Hi, Mahadev.  It seems to happen when attempting to create a new node. 
> Might be a timing issue because it does not happen all the time.  The 
> client code where this happens is quite simple:
> 
>      if (keeper.exists(path, false) == null) {
>          file = keeper.create(path, "hello".getBytes(),
>              ZooDefs.Ids.OPEN_ACL_UNSAFE, flags);
> 
>  >You are running with a standalone zookeeper server
>> right?
>>
> 
> Correct.
> 
> Thanks,
> 
> Juan
> 
> 
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2008.
> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
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> https://lists.sourceforge.net/lists/listinfo/zookeeper-user

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Juan R. <Jua...@Su...>]

Mahadev Konar wrote:
> Hi Juan,
>   Can you tell us what you are doing in your client code and when you
> see this problem?

Hi, Mahadev.  It seems to happen when attempting to create a new node. 
Might be a timing issue because it does not happen all the time.  The 
client code where this happens is quite simple:

     if (keeper.exists(path, false) == null) {
         file = keeper.create(path, "hello".getBytes(),
             ZooDefs.Ids.OPEN_ACL_UNSAFE, flags);

 >You are running with a standalone zookeeper server
> right?
>

Correct.

Thanks,

Juan

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Juan R. <Jua...@Su...>]

A bit more info in the trace file, but no obvious reason why the server 
is expiring the session:

2008-05-23 14:25:47,267 - TRACE [main:ZooTrace@68][] - Snapshotting: 0
2008-05-23 14:25:47,287 - TRACE [main:ZooTrace@68][] - Snapshotting 
finished: 0
2008-05-23 14:26:08,354 - WARN 
[NIOServerCxn.Factory:NIOServerCnxn@471][] - Connected to 
/xxx.xxx.xxx.xxx:35713 lastZxid 0
2008-05-23 14:26:08,357 - TRACE [NIOServerCxn.Factory:ZooTrace@68][] - 
SessionTrackerImpl --- Adding 11a1707891b0000 6000
2008-05-23 14:26:08,362 - WARN 
[NIOServerCxn.Factory:NIOServerCnxn@500][] - Creating new session 
11a1707891b0000
2008-05-23 14:26:08,363 - TRACE [ProcessThread:ZooTrace@87][] - 
:P11a1707891b0000 0 fffffffffffffffe  txn type = unknown createSession n/a
2008-05-23 14:26:08,369 - TRACE [ProcessThread:ZooTrace@68][] - 
SessionTrackerImpl --- Existing session 11a1707891b0000 6000
2008-05-23 14:26:08,371 - TRACE [SyncThread:ZooTrace@87][] - 
:S11a1707891b0000 0 1  txn type = -10 createSession n/a
2008-05-23 14:26:08,397 - TRACE [SyncThread:ZooTrace@87][] - 
:E11a1707891b0000 0 1  txn type = -10 createSession n/a
2008-05-23 14:26:08,400 - TRACE [SyncThread:ZooTrace@68][] - 
SessionTrackerImpl --- Existing session 11a1707891b0000 6000
2008-05-23 14:26:08,406 - WARN  [SyncThread:NIOServerCnxn@774][] - 
Finished init of 11a1707891b0000: true
2008-05-23 14:26:08,412 - TRACE [ProcessThread:ZooTrace@87][] - 
:P11a1707891b0000 1 fffffffffffffffe  txn type = unknown exists /locks
2008-05-23 14:26:08,413 - TRACE [SyncThread:ZooTrace@87][] - 
:S11a1707891b0000 1 fffffffffffffffe  txn type = unknown exists /locks
2008-05-23 14:26:08,415 - TRACE [SyncThread:ZooTrace@87][] - 
:E11a1707891b0000 1 fffffffffffffffe  txn type = unknown exists /locks
2008-05-23 14:26:14,435 - TRACE [NIOServerCxn.Factory:ZooTrace@68][] - 
close  NIOServerCnxn: java.nio.channels.SocketChannel[connected 
local=/xxx.xxx.xxx.xxx:2181 remote=/xxx.xxx.xxx.xxx:35713]
2008-05-23 14:26:15,010 - WARN 
[SessionTracker:SessionTrackerImpl@133][] - Expiring 11a1707891b0000
2008-05-23 14:26:15,012 - TRACE [SessionTracker:ZooTrace@68][] - 
ZooKeeperServer --- Session to expire: 11a1707891b0000
2008-05-23 14:26:15,013 - TRACE [SessionTracker:ZooTrace@68][] - 
ZooKeeperServer --- Session to be closed: 11a1707891b0000
2008-05-23 14:26:15,015 - TRACE [ProcessThread:ZooTrace@87][] - 
:P11a1707891b0000 0 fffffffffffffffe  txn type = unknown closeSession n/a
2008-05-23 14:26:15,017 - WARN 
[ProcessThread:PrepRequestProcessor@341][] - Processed session 
termination request for id: 11a1707891b0000
2008-05-23 14:26:15,019 - TRACE [SyncThread:ZooTrace@87][] - 
:S11a1707891b0000 0 2  txn type = -11 closeSession n/a
2008-05-23 14:26:15,023 - TRACE [SyncThread:ZooTrace@87][] - 
:E11a1707891b0000 0 2  txn type = -11 closeSession n/a
2008-05-23 14:26:15,025 - TRACE [SyncThread:ZooTrace@68][] - 
SessionTrackerImpl --- Removing 11a1707891b0000
2008-05-23 14:26:15,816 - WARN 
[NIOServerCxn.Factory:NIOServerCnxn@471][] - Connected to 
/xxx.xxx.xxx.xxx:35714 lastZxid -1
2008-05-23 14:26:15,818 - TRACE [NIOServerCxn.Factory:ZooTrace@68][] - 
Session 11a1707891b0000 is valid: false
2008-05-23 14:26:15,819 - WARN 
[NIOServerCxn.Factory:NIOServerCnxn@774][] - Finished init of 
11a1707891b0000: false
2008-05-23 14:26:15,821 - WARN 
[NIOServerCxn.Factory:NIOServerCnxn@497][] - Renewing session 
11a1707891b0000
2008-05-23 14:26:15,823 - TRACE [NIOServerCxn.Factory:ZooTrace@68][] - 
close  NIOServerCnxn: java.nio.channels.SocketChannel[connected 
local=/xxx.xxx.xxx.xxx:2181 remote=/xxx.xxx.xxx.xxx:35714]

Juan Ramirez wrote:
> Hi, Ben.  Thanks for the prompt reply.
> 
> Benjamin Reed wrote:
>> Usually, this exception means that the server closed the socket. Are you 
>> seeing anything strange in the server log?
>>
> 
> It seems like the server is expiring the session; not sure why.
> 
> 2008-05-23 14:26:08,354 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@471] 
> - Connected to /xxx.xxx.xxx.xxx:35713 lastZxid 0
> 2008-05-23 14:26:08,362 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@500] 
> - Creating new session 11a1707891b0000
> 2008-05-23 14:26:08,406 - WARN  [SyncThread:NIOServerCnxn@774] - 
> Finished init of 11a1707891b0000: true
> 2008-05-23 14:26:15,010 - WARN  [SessionTracker:SessionTrackerImpl@133] 
> - Expiring 11a1707891b0000
> 2008-05-23 14:26:15,017 - WARN  [ProcessThread:PrepRequestProcessor@341] 
> - Processed session termination request for id: 11a1707891b0000
> 
> New connection request from client?
> 
> 2008-05-23 14:26:15,816 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@471] 
> - Connected to /xxx.xxx.xxx.xxx:35714 lastZxid -1
> 2008-05-23 14:26:15,819 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@774] 
> - Finished init of 11a1707891b0000: false
> 2008-05-23 14:26:15,821 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@497] 
> - Renewing session 11a1707891b0000
> 
> But doesn't seem like the client recovers:
> 
> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
>          at com.yahoo.zookeeper.ZooKeeper.exists(ZooKeeper.java:357)
>          at zookeeperclient.Main$Process.tryCreate(Main.java:143)
>          at zookeeperclient.Main$Process.<init>(Main.java:88)
>          at zookeeperclient.Main.main(Main.java:43)
> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
>          at com.yahoo.zookeeper.ZooKeeper.exists(ZooKeeper.java:357)
>          at zookeeperclient.Main$Process.tryCreate(Main.java:143)
>          at zookeeperclient.Main$Process.<init>(Main.java:88)
>          at zookeeperclient.Main.main(Main.java:43)
> 
> 
> 
>> The null pointer exception is coming from the code that parses the hostPort 
>> list. Since you are running in standalone mode your hostPort should be a 
>> string of the form host:port. The relevant code is the following:
>>
>>         String hostsList[] = hosts.split(",");
>>         for (String host : hostsList) {
>>             int port = 2181;
>>             String parts[] = host.split(":"); // LINE 218
>>
>> It would seem that host is null, but I'm at a complete loss for how that could 
>> be...
> 
> Sorry, that was my bad.  It seems that once the ZooKeeper instance gets 
> into the SessionExpired state, it doesn't recover.  Is this expected?  I 
> had some code creating a new instance as a workaround and had not 
> properly persisted the connection string.
> 
> Thanks again,
> 
> Juan
> 
> 
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2008.
> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
> _______________________________________________
> Zookeeper-user mailing list
> Zoo...@li...
> https://lists.sourceforge.net/lists/listinfo/zookeeper-user

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Mahadev K. <ma...@ya...>]

Hi Juan,
  Can you tell us what you are doing in your client code and when you
see this problem? You are running with a standalone zookeeper server
right?

Mahadev
> -----Original Message-----
> From: zoo...@li...
[mailto:zookeeper-user-
> bo...@li...] On Behalf Of Juan Ramirez
> Sent: Friday, May 23, 2008 11:36 AM
> To: Benjamin Reed
> Cc: zoo...@li...
> Subject: Re: [Zookeeper-user] odd exceptions when using zookeeper
> 
> Hi, Ben.  Thanks for the prompt reply.
> 
> Benjamin Reed wrote:
> > Usually, this exception means that the server closed the socket. Are
you
> > seeing anything strange in the server log?
> >
> 
> It seems like the server is expiring the session; not sure why.
> 
> 2008-05-23 14:26:08,354 - WARN
[NIOServerCxn.Factory:NIOServerCnxn@471]
> - Connected to /xxx.xxx.xxx.xxx:35713 lastZxid 0
> 2008-05-23 14:26:08,362 - WARN
[NIOServerCxn.Factory:NIOServerCnxn@500]
> - Creating new session 11a1707891b0000
> 2008-05-23 14:26:08,406 - WARN  [SyncThread:NIOServerCnxn@774] -
> Finished init of 11a1707891b0000: true
> 2008-05-23 14:26:15,010 - WARN
[SessionTracker:SessionTrackerImpl@133]
> - Expiring 11a1707891b0000
> 2008-05-23 14:26:15,017 - WARN
[ProcessThread:PrepRequestProcessor@341]
> - Processed session termination request for id: 11a1707891b0000
> 
> New connection request from client?
> 
> 2008-05-23 14:26:15,816 - WARN
[NIOServerCxn.Factory:NIOServerCnxn@471]
> - Connected to /xxx.xxx.xxx.xxx:35714 lastZxid -1
> 2008-05-23 14:26:15,819 - WARN
[NIOServerCxn.Factory:NIOServerCnxn@774]
> - Finished init of 11a1707891b0000: false
> 2008-05-23 14:26:15,821 - WARN
[NIOServerCxn.Factory:NIOServerCnxn@497]
> - Renewing session 11a1707891b0000
> 
> But doesn't seem like the client recovers:
> 
> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
>          at com.yahoo.zookeeper.ZooKeeper.exists(ZooKeeper.java:357)
>          at zookeeperclient.Main$Process.tryCreate(Main.java:143)
>          at zookeeperclient.Main$Process.<init>(Main.java:88)
>          at zookeeperclient.Main.main(Main.java:43)
> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
>          at com.yahoo.zookeeper.ZooKeeper.exists(ZooKeeper.java:357)
>          at zookeeperclient.Main$Process.tryCreate(Main.java:143)
>          at zookeeperclient.Main$Process.<init>(Main.java:88)
>          at zookeeperclient.Main.main(Main.java:43)
> 
> 
> 
> > The null pointer exception is coming from the code that parses the
> hostPort
> > list. Since you are running in standalone mode your hostPort should
be a
> > string of the form host:port. The relevant code is the following:
> >
> >         String hostsList[] = hosts.split(",");
> >         for (String host : hostsList) {
> >             int port = 2181;
> >             String parts[] = host.split(":"); // LINE 218
> >
> > It would seem that host is null, but I'm at a complete loss for how
that
> could
> > be...
> 
> Sorry, that was my bad.  It seems that once the ZooKeeper instance
gets
> into the SessionExpired state, it doesn't recover.  Is this expected?
I
> had some code creating a new instance as a workaround and had not
> properly persisted the connection string.
> 
> Thanks again,
> 
> Juan
> 
> 
>
------------------------------------------------------------------------
-
> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2008.
> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
> _______________________________________________
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> https://lists.sourceforge.net/lists/listinfo/zookeeper-user

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Juan R. <Jua...@Su...>]

Hi, Ben.  Thanks for the prompt reply.

Benjamin Reed wrote:
> Usually, this exception means that the server closed the socket. Are you 
> seeing anything strange in the server log?
> 

It seems like the server is expiring the session; not sure why.

2008-05-23 14:26:08,354 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@471] 
- Connected to /xxx.xxx.xxx.xxx:35713 lastZxid 0
2008-05-23 14:26:08,362 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@500] 
- Creating new session 11a1707891b0000
2008-05-23 14:26:08,406 - WARN  [SyncThread:NIOServerCnxn@774] - 
Finished init of 11a1707891b0000: true
2008-05-23 14:26:15,010 - WARN  [SessionTracker:SessionTrackerImpl@133] 
- Expiring 11a1707891b0000
2008-05-23 14:26:15,017 - WARN  [ProcessThread:PrepRequestProcessor@341] 
- Processed session termination request for id: 11a1707891b0000

New connection request from client?

2008-05-23 14:26:15,816 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@471] 
- Connected to /xxx.xxx.xxx.xxx:35714 lastZxid -1
2008-05-23 14:26:15,819 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@774] 
- Finished init of 11a1707891b0000: false
2008-05-23 14:26:15,821 - WARN  [NIOServerCxn.Factory:NIOServerCnxn@497] 
- Renewing session 11a1707891b0000

But doesn't seem like the client recovers:

com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
         at com.yahoo.zookeeper.ZooKeeper.exists(ZooKeeper.java:357)
         at zookeeperclient.Main$Process.tryCreate(Main.java:143)
         at zookeeperclient.Main$Process.<init>(Main.java:88)
         at zookeeperclient.Main.main(Main.java:43)
com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
         at com.yahoo.zookeeper.ZooKeeper.exists(ZooKeeper.java:357)
         at zookeeperclient.Main$Process.tryCreate(Main.java:143)
         at zookeeperclient.Main$Process.<init>(Main.java:88)
         at zookeeperclient.Main.main(Main.java:43)



> The null pointer exception is coming from the code that parses the hostPort 
> list. Since you are running in standalone mode your hostPort should be a 
> string of the form host:port. The relevant code is the following:
> 
>         String hostsList[] = hosts.split(",");
>         for (String host : hostsList) {
>             int port = 2181;
>             String parts[] = host.split(":"); // LINE 218
> 
> It would seem that host is null, but I'm at a complete loss for how that could 
> be...

Sorry, that was my bad.  It seems that once the ZooKeeper instance gets 
into the SessionExpired state, it doesn't recover.  Is this expected?  I 
had some code creating a new instance as a workaround and had not 
properly persisted the connection string.

Thanks again,

Juan

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Benjamin R. <br...@ya...>]

Usually, this exception means that the server closed the socket. Are you 
seeing anything strange in the server log?

The null pointer exception is coming from the code that parses the hostPort 
list. Since you are running in standalone mode your hostPort should be a 
string of the form host:port. The relevant code is the following:

        String hostsList[] = hosts.split(",");
        for (String host : hostsList) {
            int port = 2181;
            String parts[] = host.split(":"); // LINE 218

It would seem that host is null, but I'm at a complete loss for how that could 
be...

ben

On Friday 23 May 2008 07:27:11 Juan Ramirez wrote:
> I see this sometimes as well:
>
> java.lang.RuntimeException: Unreasonable length = -183042030
>          at
> com.yahoo.jute.BinaryInputArchive.readBuffer(BinaryInputArchive.java:101)
>          at
> com.yahoo.zookeeper.proto.ConnectResponse.deserialize(ConnectResponse.java:
>59) at
> com.yahoo.zookeeper.ClientCnxn$SendThread.readConnectResult(ClientCnxn.java
>:400) at
> com.yahoo.zookeeper.ClientCnxn$SendThread.doIO(ClientCnxn.java:492)
>          at
> com.yahoo.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:705)
>
> Juan Ramirez wrote:
> > Forgot to mention, I am using the zookeeper-2.2.0.jar distribution.
> >
> > Juan Ramirez wrote:
> >> Hi, I am trying to become familiar with the zookeeper API and am seeing
> >> the following exceptions when attempting to create a node; any pointers
> >> as to where to look for their cause would be greatly appreciated.
> >>
> >> AFAIK, I am not doing anything special.  I am running ZK standalone
> >> using JDK 1.6 and attempting to connect to it and create some nodes.
> >> Other than dataDir, I am using the configuration values in
> >> zoo_sample.cfg.  My attempt to create the nodes succeed sometimes, but
> >> more often than not, I get some fashion of "Session Expired" errors.  I
> >> am following com.yahoo.zookeeper.ZooKeeper.main() example and using
> >> 5000ms for the client-side sessionTimeout.  Thanks in advance.
> >>
> >> These happen in sequence:
> >>
> >> java.io.IOException: TIMED OUT
> >>         at
> >> com.yahoo.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:666)
> >> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = ConnectionLoss
> >> for /locks/
> >>         at com.yahoo.zookeeper.ZooKeeper.create(ZooKeeper.java:244)
> >>         at zookeeperclient.Main$Process.tryCreate(Main.java:142)
> >>         at zookeeperclient.Main$Process.<init>(Main.java:87)
> >>         at zookeeperclient.Main.main(Main.java:43)
> >>
> >> java.io.IOException: Read error rc = -1 java.nio.DirectByteBuffer[pos=0
> >> lim=4 cap=4]
> >>         at
> >> com.yahoo.zookeeper.ClientCnxn$SendThread.doIO(ClientCnxn.java:484)
> >>         at
> >> com.yahoo.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:705)
> >>
> >> java.lang.NullPointerException
> >>         at com.yahoo.zookeeper.ClientCnxn.<init>(ClientCnxn.java:218)
> >>         at com.yahoo.zookeeper.ClientCnxn.<init>(ClientCnxn.java:194)
> >>         at com.yahoo.zookeeper.ZooKeeper.<init>(ZooKeeper.java:123)
> >>         at zookeeperclient.Main$Process.tryCreate(Main.java:151)
> >>         at zookeeperclient.Main$Process.<init>(Main.java:87)
> >>         at zookeeperclient.Main.main(Main.java:43)
> >> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired
> >> for /locks/
> >>         at com.yahoo.zookeeper.ZooKeeper.create(ZooKeeper.java:244)
> >>         at zookeeperclient.Main$Process.tryCreate(Main.java:142)
> >>         at zookeeperclient.Main$Process.<init>(Main.java:87)
> >>         at zookeeperclient.Main.main(Main.java:43)
> >
> > -------------------------------------------------------------------------
> > This SF.net email is sponsored by: Microsoft
> > Defy all challenges. Microsoft(R) Visual Studio 2008.
> > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
> > _______________________________________________
> > Zookeeper-user mailing list
> > Zoo...@li...
> > https://lists.sourceforge.net/lists/listinfo/zookeeper-user
>
> -------------------------------------------------------------------------
> This SF.net email is sponsored by: Microsoft
> Defy all challenges. Microsoft(R) Visual Studio 2008.
> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
> _______________________________________________
> Zookeeper-user mailing list
> Zoo...@li...
> https://lists.sourceforge.net/lists/listinfo/zookeeper-user

Re: [Zookeeper-user] odd exceptions when using zookeeper

[Juan R. <Jua...@Su...>]

I see this sometimes as well:

java.lang.RuntimeException: Unreasonable length = -183042030
         at 
com.yahoo.jute.BinaryInputArchive.readBuffer(BinaryInputArchive.java:101)
         at 
com.yahoo.zookeeper.proto.ConnectResponse.deserialize(ConnectResponse.java:59)
         at 
com.yahoo.zookeeper.ClientCnxn$SendThread.readConnectResult(ClientCnxn.java:400)
         at 
com.yahoo.zookeeper.ClientCnxn$SendThread.doIO(ClientCnxn.java:492)
         at 
com.yahoo.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:705)

Juan Ramirez wrote:
> Forgot to mention, I am using the zookeeper-2.2.0.jar distribution.
> 
> Juan Ramirez wrote:
>> Hi, I am trying to become familiar with the zookeeper API and am seeing 
>> the following exceptions when attempting to create a node; any pointers 
>> as to where to look for their cause would be greatly appreciated.
>>
>> AFAIK, I am not doing anything special.  I am running ZK standalone 
>> using JDK 1.6 and attempting to connect to it and create some nodes. 
>> Other than dataDir, I am using the configuration values in 
>> zoo_sample.cfg.  My attempt to create the nodes succeed sometimes, but 
>> more often than not, I get some fashion of "Session Expired" errors.  I 
>> am following com.yahoo.zookeeper.ZooKeeper.main() example and using 
>> 5000ms for the client-side sessionTimeout.  Thanks in advance.
>>
>> These happen in sequence:
>>
>> java.io.IOException: TIMED OUT
>>         at 
>> com.yahoo.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:666)
>> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = ConnectionLoss 
>> for /locks/
>>         at com.yahoo.zookeeper.ZooKeeper.create(ZooKeeper.java:244)
>>         at zookeeperclient.Main$Process.tryCreate(Main.java:142)
>>         at zookeeperclient.Main$Process.<init>(Main.java:87)
>>         at zookeeperclient.Main.main(Main.java:43)
>>
>> java.io.IOException: Read error rc = -1 java.nio.DirectByteBuffer[pos=0 
>> lim=4 cap=4]
>>         at 
>> com.yahoo.zookeeper.ClientCnxn$SendThread.doIO(ClientCnxn.java:484)
>>         at 
>> com.yahoo.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:705)
>>
>> java.lang.NullPointerException
>>         at com.yahoo.zookeeper.ClientCnxn.<init>(ClientCnxn.java:218)
>>         at com.yahoo.zookeeper.ClientCnxn.<init>(ClientCnxn.java:194)
>>         at com.yahoo.zookeeper.ZooKeeper.<init>(ZooKeeper.java:123)
>>         at zookeeperclient.Main$Process.tryCreate(Main.java:151)
>>         at zookeeperclient.Main$Process.<init>(Main.java:87)
>>         at zookeeperclient.Main.main(Main.java:43)
>> com.yahoo.zookeeper.KeeperException: KeeperErrorCode = SessionExpired 
>> for /locks/
>>         at com.yahoo.zookeeper.ZooKeeper.create(ZooKeeper.java:244)
>>         at zookeeperclient.Main$Process.tryCreate(Main.java:142)
>>         at zookeeperclient.Main$Process.<init>(Main.java:87)
>>         at zookeeperclient.Main.main(Main.java:43)
>>
> 
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