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From lars hofhansl <la...@apache.org>
Subject Re: HBase Table Row Count Optimization - A Solicitation For Help
Date Sat, 21 Sep 2013 01:09:06 GMT
>From your numbers below you have about 26k regions, thus each region is about 545tb/26k
= 20gb. Good.

How many mappers are you running?
And just to rule out the obvious, the M/R is running on the cluster and not locally, right?
(it will default to a local runner when it cannot use the M/R cluster).

Some back of the envelope calculations tell me that assuming 1ge network cards, the best you
can expect for 110 machines to map through this data is about 10h. (so way faster than what
you see).
(545tb/(110*1/8gb/s) ~ 40ks ~11h)


We should really add a rowcounting coprocessor to HBase and allow using it via M/R.

-- Lars



________________________________
 From: James Birchfield <jbirchfield@stumbleupon.com>
To: user@hbase.apache.org 
Sent: Friday, September 20, 2013 5:09 PM
Subject: Re: HBase Table Row Count Optimization - A Solicitation For Help
 

I did not implement accurate timing, but the current table being counted has been running
for about 10 hours, and the log is estimating the map portion at 10%

2013-09-20 23:40:24,099 INFO  [main] Job                            :  map
10% reduce 0%

So a loooong time.  Like I mentioned, we have billions, if not trillions of rows potentially.

Thanks for the feedback on the approaches I mentioned.  I was not sure if they would have
any effect overall.

I will look further into coprocessors.

Thanks!
Birch
On Sep 20, 2013, at 4:58 PM, Vladimir Rodionov <vrodionov@carrieriq.com> wrote:

> How long does it take for RowCounter Job for largest table to finish on your cluster?
> 
> Just curious.
> 
> On your options:
> 
> 1. Not worth it probably - you may overload your cluster
> 2. Not sure this one differs from 1. Looks the same to me but more complex.
> 3. The same as 1 and 2
> 
> Counting rows in efficient way can be done if you sacrifice some accuracy :
> 
> http://highscalability.com/blog/2012/4/5/big-data-counting-how-to-count-a-billion-distinct-objects-us.html
> 
> Yeah, you will need coprocessors for that.
> 
> Best regards,
> Vladimir Rodionov
> Principal Platform Engineer
> Carrier IQ, www.carrieriq.com
> e-mail: vrodionov@carrieriq.com
> 
> ________________________________________
> From: James Birchfield [jbirchfield@stumbleupon.com]
> Sent: Friday, September 20, 2013 3:50 PM
> To: user@hbase.apache.org
> Subject: Re: HBase Table Row Count Optimization - A Solicitation For Help
> 
> Hadoop 2.0.0-cdh4.3.1
> 
> HBase 0.94.6-cdh4.3.1
> 
> 110 servers, 0 dead, 238.2364 average load
> 
> Some other info, not sure if it helps or not.
> 
> Configured Capacity: 1295277834158080 (1.15 PB)
> Present Capacity: 1224692609430678 (1.09 PB)
> DFS Remaining: 624376503857152 (567.87 TB)
> DFS Used: 600316105573526 (545.98 TB)
> DFS Used%: 49.02%
> Under replicated blocks: 0
> Blocks with corrupt replicas: 1
> Missing blocks: 0
> 
> It is hitting a production cluster, but I am not really sure how to calculate the load
placed on the cluster.
> On Sep 20, 2013, at 3:19 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> 
>> How many nodes do you have in your cluster ?
>> 
>> When counting rows, what other load would be placed on the cluster ?
>> 
>> What is the HBase version you're currently using / planning to use ?
>> 
>> Thanks
>> 
>> 
>> On Fri, Sep 20, 2013 at 2:47 PM, James Birchfield <
>> jbirchfield@stumbleupon.com> wrote:
>> 
>>>       After reading the documentation and scouring the mailing list
>>> archives, I understand there is no real support for fast row counting in
>>> HBase unless you build some sort of tracking logic into your code.  In our
>>> case, we do not have such logic, and have massive amounts of data already
>>> persisted.  I am running into the issue of very long execution of the
>>> RowCounter MapReduce job against very large tables (multi-billion for many
>>> is our estimate).  I understand why this issue exists and am slowly
>>> accepting it, but I am hoping I can solicit some possible ideas to help
>>> speed things up a little.
>>> 
>>>       My current task is to provide total row counts on about 600
>>> tables, some extremely large, some not so much.  Currently, I have a
>>> process that executes the MapRduce job in process like so:
>>> 
>>>                       Job job = RowCounter.createSubmittableJob(
>>>                                       ConfigManager.getConfiguration(),
>>> new String[]{tableName});
>>>                       boolean waitForCompletion =
>>> job.waitForCompletion(true);
>>>                       Counters counters = job.getCounters();
>>>                       Counter rowCounter =
>>> counters.findCounter(hbaseadminconnection.Counters.ROWS);
>>>                       return rowCounter.getValue();
>>> 
>>>       At the moment, each MapReduce job is executed in serial order, so
>>> counting one table at a time.  For the current implementation of this whole
>>> process, as it stands right now, my rough timing calculations indicate that
>>> fully counting all the rows of these 600 tables will take anywhere between
>>> 11 to 22 days.  This is not what I consider a desirable timeframe.
>>> 
>>>       I have considered three alternative approaches to speed things up.
>>> 
>>>       First, since the application is not heavily CPU bound, I could use
>>> a ThreadPool and execute multiple MapReduce jobs at the same time looking
>>> at different tables.  I have never done this, so I am unsure if this would
>>> cause any unanticipated side effects.
>>> 
>>>       Second, I could distribute the processes.  I could find as many
>>> machines that can successfully talk to the desired cluster properly, give
>>> them a subset of tables to work on, and then combine the results post
>>> process.
>>> 
>>>       Third, I could combine both the above approaches and run a
>>> distributed set of multithreaded process to execute the MapReduce jobs in
>>> parallel.
>>> 
>>>       Although it seems to have been asked and answered many times, I
>>> will ask once again.  Without the need to change our current configurations
>>> or restart the clusters, is there a faster approach to obtain row counts?
>>> FYI, my cache size for the Scan is set to 1000.  I have experimented with
>>> different numbers, but nothing made a noticeable difference.  Any advice or
>>> feedback would be greatly appreciated!
>>> 
>>> Thanks,
>>> Birch
> 
> 
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