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From Tatsuya Kawano <tatsuya6...@gmail.com>
Subject Re: Cluster Wide Pauses
Date Thu, 13 Jan 2011 11:59:56 GMT

Hi Wayne, 

> We are seeing some TCP Resets on all nodes at the same time, and sometimes
> quite a lot of them. 

Have you checked this article from Andrei and Cosmin? They had a busy firewall to cause network


Maybe it's not your case but just for sure. 


Tatsuya Kawano (Mr.)
Tokyo, Japan

On Jan 13, 2011, at 4:52 AM, Wayne <wav100@gmail.com> wrote:

> We are seeing some TCP Resets on all nodes at the same time, and sometimes
> quite a lot of them. We have yet to correlate the pauses to the TCP resets
> but I am starting to wonder if this is partly a network problem. Does
> Gigabit Ethernet break down on high volume nodes? Do high volume nodes use
> 10G or Infiniband?
> On Wed, Jan 12, 2011 at 1:52 PM, Stack <stack@duboce.net> wrote:
>> Jon asks that you describe your loading in the issue.  Would you mind
>> doing so.  Ted, stick up in the issue the workload and configs. you
>> are running if you don't mind.  I'd like to try it over here.
>> Thanks lads,
>> St.Ack
>> On Wed, Jan 12, 2011 at 9:03 AM, Wayne <wav100@gmail.com> wrote:
>>> Added: https://issues.apache.org/jira/browse/HBASE-3438.
>>> On Wed, Jan 12, 2011 at 11:40 AM, Wayne <wav100@gmail.com> wrote:
>>>> We are using 0.89.20100924, r1001068
>>>> We are seeing see it during heavy write load (which is all the time),
>> but
>>>> yesterday we had read load as well as write load and saw both reads and
>>>> writes stop for 10+ seconds. The region size is the biggest clue we have
>>>> found from our tests as setting up a new cluster with a 1GB max region
>> size
>>>> and starting to load heavily we will see this a lot for long long time
>>>> frames. Maybe the bigger file gets hung up more easily with a split?
>> Your
>>>> description below also fits in that early on the load is not balanced so
>> it
>>>> is easier to stop everything on one node as the balance is not great
>> early
>>>> on. I will file a JIRA. I will also try to dig deeper into the logs
>> during
>>>> the pauses to find a node that might be stuck in a split.
>>>> On Wed, Jan 12, 2011 at 11:17 AM, Stack <stack@duboce.net> wrote:
>>>>> On Tue, Jan 11, 2011 at 2:34 PM, Wayne <wav100@gmail.com> wrote:
>>>>>> We have very frequent cluster wide pauses that stop all reads and
>>>>> writes
>>>>>> for seconds.
>>>>> All reads and all writes?
>>>>> I've seen the pause too for writes.  Its something I've always meant
>>>>> to look into.  Friso postulates one cause.  Another that we've talked
>>>>> of is a region taking a while to come back on line after a split or a
>>>>> rebalance for whatever reason.  Client loading might be 'random'
>>>>> spraying over lots of random regions but they all get stuck waiting on
>>>>> one particular region to come back online.
>>>>> I suppose reads could be blocked for same reason if all are trying to
>>>>> read from the offlined region.
>>>>> What version of hbase are you using?  Splits should be faster in 0.90
>>>>> now that the split daughters come up on the same region.
>>>>> Sorry I don't have a better answer for you.  Need to dig in.
>>>>> File a JIRA.  If you want to help out some, stick some data up in it.
>>>>> Some suggestions would be to enable logging of when we lookup region
>>>>> locations in client and then note when requests go to zero.  Can you
>>>>> figure what region the clients are waiting on (if they are waiting on
>>>>> any).  If you can pull out a particular one, try and elicit its
>>>>> history at time of blockage.  Is it being moved or mid-split?  I
>>>>> suppose it makes sense that bigger regions would make the situation
>>>>> 'worse'.  I can take a look at it too.
>>>>> St.Ack
>>>>> We are constantly loading data to this cluster of 10 nodes.
>>>>>> These pauses can happen as frequently as every minute but sometimes
>> are
>>>>> not
>>>>>> seen for 15+ minutes. Basically watching the Region server list with
>>>>> request
>>>>>> counts is the only evidence of what is going on. All reads and writes
>>>>>> totally stop and if there is ever any activity it is on the node
>> hosting
>>>>> the
>>>>>> .META. table with a request count of region count + 1. This problem
>>>>> seems to
>>>>>> be worse with a larger region size. We tried a 1GB region size and
>> saw
>>>>> this
>>>>>> more than we saw actual activity (and stopped using a larger region
>> size
>>>>>> because of it). We went back to the default region size and it was
>>>>> better,
>>>>>> but we had too many regions so now we are up to 512M for a region
>> size
>>>>> and
>>>>>> we are seeing it more again.
>>>>>> Does anyone know what this is? We have dug into all of the logs to
>> find
>>>>> some
>>>>>> sort of pause but are not able to find anything. Is this an wal hlog
>>>>> roll?
>>>>>> Is this a region split or compaction? Of course our biggest fear
is a
>> GC
>>>>>> pause on the master but we do not have java logging turned on with
>> the
>>>>>> master to tell. What could possibly stop the entire cluster from
>> working
>>>>> for
>>>>>> seconds at a time very frequently?
>>>>>> Thanks in advance for any ideas of what could be causing this.

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