we do have the ability to compress the data. I am not sure if there is a easy way to turn on/off the compression.
On Wed, Feb 4, 2015 at 2:49 PM, Varun Sharma <[email protected]> wrote: > 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 <[email protected]> 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" <[email protected]> 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 <[email protected]> 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 [[email protected]] >>>> *Sent:* Monday, February 02, 2015 4:41 PM >>>> *To:* [email protected] >>>> *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.zk >>>> client.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 <[email protected]> >>>> 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 <[email protected]> >>>>> 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 >>>>>> >>>>>> >>>>>> >>>>> >>>> >>> >
