helix-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Varun Sharma <va...@pinterest.com>
Subject Re: Excessive ZooKeeper load
Date Wed, 04 Feb 2015 22:49:45 GMT
I am wondering if its possible to gzip the external view znode - a simple
gzip cut down the data size by 25X. Is it possible to plug in
compression/decompression as zookeeper nodes are read ?

Varun

On Mon, Feb 2, 2015 at 8:53 PM, kishore g <g.kishore@gmail.com> wrote:

> There are multiple options we can try here.
> what if we used cacheddataaccessor for this use case?.clients will only
> read if node has changed. This optimization can benefit all use cases.
>
> What about batching the watch triggers. Not sure which version of helix
> has this option.
>
> Another option is to use a poll based roundtable instead of watch based.
> This can coupled with cacheddataaccessor can be over efficient.
>
> Thanks,
> Kishore G
> On Feb 2, 2015 8:17 PM, "Varun Sharma" <varun@pinterest.com> wrote:
>
>> My total external view across all resources is roughly 3M in size and
>> there are 100 clients downloading it twice for every node restart - thats
>> 600M of data for every restart. So I guess that is causing this issue. We
>> are thinking of doing some tricks to limit the # of clients to 1 from 100.
>> I guess that should help significantly.
>>
>> Varun
>>
>> On Mon, Feb 2, 2015 at 7:37 PM, Zhen Zhang <zzhang@linkedin.com> wrote:
>>
>>>  Hey Varun,
>>>
>>>  I guess your external view is pretty large, since each external view
>>> callback takes ~3s. The RoutingTableProvider is callback based, so only
>>> when there is a change in the external view, RoutingTableProvider will read
>>> the entire external view from ZK. During the rolling upgrade, there are
>>> lots of live instance change, which may lead to a lot of changes in the
>>> external view. One possible way to mitigate the issue is to smooth the
>>> traffic by having some delays in between bouncing nodes. We can do a rough
>>> estimation on how many external view changes you might have during the
>>> upgrade, how many listeners you have, and how large is the external views.
>>> Once we have these numbers, we might know the ZK bandwidth requirement. ZK
>>> read bandwidth can be scaled by adding ZK observers.
>>>
>>>  ZK watcher is one time only, so every time a listener receives a
>>> callback, it will re-register its watcher again to ZK.
>>>
>>>  It's normally unreliable to depend on delta changes instead of reading
>>> the entire znode. There might be some corner cases where you would lose
>>> delta changes if you depend on that.
>>>
>>>  For the ZK connection issue, do you have any log on the ZK server side
>>> regarding this connection?
>>>
>>>  Thanks,
>>> Jason
>>>
>>>   ------------------------------
>>> *From:* Varun Sharma [varun@pinterest.com]
>>> *Sent:* Monday, February 02, 2015 4:41 PM
>>> *To:* user@helix.apache.org
>>> *Subject:* Re: Excessive ZooKeeper load
>>>
>>>   I believe there is a misbehaving client. Here is a stack trace - it
>>> probably lost connection and is now stampeding it:
>>>
>>>  "ZkClient-EventThread-104-terrapinzk001a:2181,terrapinzk
>>> 002b:2181,terrapinzk003e:2181" daemon prio=10 tid=0x00007f534144b800
>>> nid=0x7db5 in Object.wait() [0x00007f52ca9c3000]
>>>
>>>    java.lang.Thread.State: WAITING (on object monitor)
>>>
>>>         at java.lang.Object.wait(Native Method)
>>>
>>>         at java.lang.Object.wait(Object.java:503)
>>>
>>>         at
>>> org.apache.zookeeper.ClientCnxn.submitRequest(ClientCnxn.java:1309)
>>>
>>>         - locked <0x00000004fb0d8c38> (a
>>> org.apache.zookeeper.ClientCnxn$Packet)
>>>
>>>         at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1036)
>>>
>>>         at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1069)
>>>
>>>         at org.I0Itec.zkclient.ZkConnection.exists(ZkConnection.java:95)
>>>
>>>         at org.I0Itec.zkclient.ZkClient$11.call(ZkClient.java:823)
>>>
>>> *        at
>>> org.I0Itec.zkclient.ZkClient.retryUntilConnected(ZkClient.java:675)*
>>>
>>> *        at org.I0Itec.zkclient.ZkClient.watchForData(ZkClient.java:820)*
>>>
>>> *        at
>>> org.I0Itec.zkclient.ZkClient.subscribeDataChanges(ZkClient.java:136)*
>>>
>>>         at org.apache.helix.manager.zk
>>> .CallbackHandler.subscribeDataChange(CallbackHandler.java:241)
>>>
>>>         at org.apache.helix.manager.zk
>>> .CallbackHandler.subscribeForChanges(CallbackHandler.java:287)
>>>
>>>         at org.apache.helix.manager.zk
>>> .CallbackHandler.invoke(CallbackHandler.java:202)
>>>
>>>         - locked <0x000000056b75a948> (a org.apache.helix.manager.zk
>>> .ZKHelixManager)
>>>
>>>         at org.apache.helix.manager.zk
>>> .CallbackHandler.handleDataChange(CallbackHandler.java:338)
>>>
>>>         at org.I0Itec.zkclient.ZkClient$6.run(ZkClient.java:547)
>>>
>>>         at org.I0Itec.zkclient.ZkEventThread.run(ZkEventThread.java:71)
>>>
>>> On Mon, Feb 2, 2015 at 4:28 PM, Varun Sharma <varun@pinterest.com>
>>> wrote:
>>>
>>>> I am wondering what is causing the zk subscription to happen every 2-3
>>>> seconds - is this a new watch being established every 3 seconds ?
>>>>
>>>>  Thanks
>>>>  Varun
>>>>
>>>> On Mon, Feb 2, 2015 at 4:23 PM, Varun Sharma <varun@pinterest.com>
>>>> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>>  We are serving a few different resources whose total # of partitions
>>>>> is ~ 30K. We just did a rolling restart fo the cluster and the clients
>>>>> which use the RoutingTableProvider are stuck in a bad state where they
are
>>>>> constantly subscribing to changes in the external view of a cluster.
Here
>>>>> is the helix log on the client after our rolling restart was finished
- the
>>>>> client is constantly polling ZK. The zookeeper node is pushing 300mbps
>>>>> right now and most of the traffic is being pulled by clients. Is this
a
>>>>> race condition - also is there an easy way to make the clients not poll
so
>>>>> aggressively. We restarted one of the clients and we don't see these
same
>>>>> messages anymore. Also is it possible to just propagate external view
diffs
>>>>> instead of the whole big znode ?
>>>>>
>>>>>  15/02/03 00:21:18 INFO zk.CallbackHandler: 104 END:INVOKE
>>>>> /main_a/EXTERNALVIEW
>>>>> listener:org.apache.helix.spectator.RoutingTableProvider Took: 3340ms
>>>>>
>>>>> 15/02/03 00:21:18 INFO zk.CallbackHandler: 104 START:INVOKE
>>>>> /main_a/EXTERNALVIEW
>>>>> listener:org.apache.helix.spectator.RoutingTableProvider
>>>>>
>>>>> 15/02/03 00:21:18 INFO zk.CallbackHandler: pinacle2084 subscribes
>>>>> child-change. path: /main_a/EXTERNALVIEW, listener:
>>>>> org.apache.helix.spectator.RoutingTableProvider@76984879
>>>>>
>>>>> 15/02/03 00:21:22 INFO zk.CallbackHandler: 104 END:INVOKE
>>>>> /main_a/EXTERNALVIEW
>>>>> listener:org.apache.helix.spectator.RoutingTableProvider Took: 3371ms
>>>>>
>>>>> 15/02/03 00:21:22 INFO zk.CallbackHandler: 104 START:INVOKE
>>>>> /main_a/EXTERNALVIEW
>>>>> listener:org.apache.helix.spectator.RoutingTableProvider
>>>>>
>>>>> 15/02/03 00:21:22 INFO zk.CallbackHandler: pinacle2084 subscribes
>>>>> child-change. path: /main_a/EXTERNALVIEW, listener:
>>>>> org.apache.helix.spectator.RoutingTableProvider@76984879
>>>>>
>>>>> 15/02/03 00:21:25 INFO zk.CallbackHandler: 104 END:INVOKE
>>>>> /main_a/EXTERNALVIEW
>>>>> listener:org.apache.helix.spectator.RoutingTableProvider Took: 3281ms
>>>>>
>>>>> 15/02/03 00:21:25 INFO zk.CallbackHandler: 104 START:INVOKE
>>>>> /main_a/EXTERNALVIEW
>>>>> listener:org.apache.helix.spectator.RoutingTableProvider
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>

Mime
View raw message