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From Camille Fournier <cami...@apache.org>
Subject Re: ephemeral node not removed after the client session is long gone
Date Wed, 28 Sep 2011 00:42:54 GMT
This:

HashSet<String> es = zks.getZKDatabase()
.getEphemerals(request.sessionId);

Is outside the synchronized block that deletes the ephemerals:

                synchronized (zks.outstandingChanges) {
    for (ChangeRecord c : zks.outstandingChanges) {
    if (c.stat == null) {                            // Doing a delete
                           es.remove(c.path);                     
  }
else if (c.stat.getEphemeralOwner() == request.sessionId) {
                es.add(c.path);                        }
     }                    for (String path2Delete : es) {
          addChangeRecord(new ChangeRecord(txnHeader.getZxid(),
                        path2Delete, null, 0, null));
  }                }
On Tue, Sep 27, 2011 at 7:26 PM, Mahadev Konar <mahadev@hortonworks.com> wrote:
> Camille,
>  I am a little confused on the explanation/text. Probably might want
> to update the jira (if kishore opens one) with a little more detail.
>
> thanks
> mahadev
>
> On Tue, Sep 27, 2011 at 2:20 PM, Fournier, Camille F.
> <Camille.Fournier@gs.com> wrote:
>> So, the node was created by 0x13220b93e610550 at 12:17:56, then that session closed
at 12:17:57, the node did not delete, and a bunch of other sessions later tried to create
the node. These sessions got nodeexists failures I presume?
>>
>>
>> Forgive the block of text I'm going to write instead of code:
>>
>> I'm going to bet that the problem lies in PrepRequestProcessor. If we get the ephemerals
for the session while an ephemeral is still in outstandingChanges and has not been committed,
then another thread commits that ephemeral and removes it from outstanding changes before
synchronizing in the outstandingChagnes block, we could never put it in the ephemeral set
that we are using to reflect ephemerals to delete. I think we need to move the synchronized
block up before we get the ephemerals from the database. But this is a bit of speculation
at the moment. Can you create a JIRA tracker for me to look at this?
>>
>> Thanks,
>> C
>>
>>
>>
>> -----Original Message-----
>> From: kishore g [mailto:g.kishore@gmail.com]
>> Sent: Monday, September 26, 2011 1:07 AM
>> To: user@zookeeper.apache.org
>> Subject: Re: ephemeral node not removed after the client session is long gone
>>
>> Hi,
>>
>> I got the following information from the logs.
>>
>> The node that still exists is
>> /kafka-tracking/consumers/UserPerformanceEvent-<host>/owners/UserPerformanceEvent/529-7
>>
>> I saw that the ephemeral owner is 86167322861045079 which is session id
>> 0x13220b93e610550.
>>
>> After searching in the transaction log of one of the ZK servers found that
>> session expired
>>
>> 9/22/11 12:17:57 PM PDT session 0x13220b93e610550 cxid 0x74 zxid 0x601bd36f7
>> closeSession null
>>
>> On digging further into the logs I found that there were multiple sessions
>> created in quick succession and every session tried to create the same node.
>> But i verified that the sessions were closed and opened in order
>> 9/22/11 12:17:56 PM PDT session 0x13220b93e610550 cxid 0x0 zxid 0x601bd36b5
>> createSession 6000
>> 9/22/11 12:17:57 PM PDT session 0x13220b93e610550 cxid 0x74 zxid 0x601bd36f7
>> closeSession null
>> 9/22/11 12:17:58 PM PDT session 0x13220b93e610551 cxid 0x0 zxid 0x601bd36f8
>> createSession 6000
>> 9/22/11 12:17:59 PM PDT session 0x13220b93e610551 cxid 0x74 zxid 0x601bd373a
>> closeSession null
>> 9/22/11 12:18:00 PM PDT session 0x13220b93e610552 cxid 0x0 zxid 0x601bd373e
>> createSession 6000
>> 9/22/11 12:18:01 PM PDT session 0x13220b93e610552 cxid 0x6c zxid 0x601bd37a0
>> closeSession null
>> 9/22/11 12:18:02 PM PDT session 0x13220b93e610553 cxid 0x0 zxid 0x601bd37e9
>> createSession 6000
>> 9/22/11 12:18:03 PM PDT session 0x13220b93e610553 cxid 0x74 zxid 0x601bd382b
>> closeSession null
>> 9/22/11 12:18:04 PM PDT session 0x13220b93e610554 cxid 0x0 zxid 0x601bd383c
>> createSession 6000
>> 9/22/11 12:18:05 PM PDT session 0x13220b93e610554 cxid 0x6a zxid 0x601bd388f
>> closeSession null
>> 9/22/11 12:18:06 PM PDT session 0x13220b93e610555 cxid 0x0 zxid 0x601bd3895
>> createSession 6000
>> 9/22/11 12:18:07 PM PDT session 0x13220b93e610555 cxid 0x6a zxid 0x601bd38cd
>> closeSession null
>> 9/22/11 12:18:10 PM PDT session 0x13220b93e610556 cxid 0x0 zxid 0x601bd38d1
>> createSession 6000
>> 9/22/11 12:18:11 PM PDT session 0x13220b93e610557 cxid 0x0 zxid 0x601bd38f2
>> createSession 6000
>> 9/22/11 12:18:11 PM PDT session 0x13220b93e610557 cxid 0x51 zxid 0x601bd396a
>> closeSession null
>>
>> Here is the log output for the sessions that tried creating the same node
>>
>> 9/22/11 12:17:54 PM PDT session 0x13220b93e61054f cxid 0x42 zxid 0x601bd366b
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:17:56 PM PDT session 0x13220b93e610550 cxid 0x42 zxid 0x601bd36ce
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:17:58 PM PDT session 0x13220b93e610551 cxid 0x42 zxid 0x601bd3711
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:18:00 PM PDT session 0x13220b93e610552 cxid 0x42 zxid 0x601bd3777
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:18:02 PM PDT session 0x13220b93e610553 cxid 0x42 zxid 0x601bd3802
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:18:05 PM PDT session 0x13220b93e610554 cxid 0x44 zxid 0x601bd385d
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:18:07 PM PDT session 0x13220b93e610555 cxid 0x44 zxid 0x601bd38b0
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>> 9/22/11 12:18:11 PM PDT session 0x13220b93e610557 cxid 0x52 zxid 0x601bd396b
>> create
>> '/kafka-tracking/consumers/UserPerformanceEvent-<hostname>/owners/UserPerformanceEvent/529-7
>>
>> Let me know if you need additional information.
>>
>> Thanks,
>> Kishore G
>>
>> On Sun, Sep 25, 2011 at 12:56 PM, Camille Fournier <camille@apache.org>wrote:
>>
>>> Can you give us more details, like the information on the client that
>>> created it, any logs around the time they created it/disconnected,
>>> etc?
>>>
>>> On Sun, Sep 25, 2011 at 2:54 PM, Jun Rao <junrao@gmail.com> wrote:
>>> > Hi,
>>> >
>>> > We found our ZK server in a state where an ephemeral node still exists
>>> after
>>> > a client session is long gone. I used the cons command on each ZK host to
>>> > list all connections and couldn't find the ephemeralOwner id. We are
>>> using
>>> > ZK 3.3.3. Has anyone seen this problem?
>>> >
>>> > Thanks,
>>> >
>>> > Jun
>>> >
>>>
>>
>

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