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HBase >> mail # user >> Coprocessor Increments


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Re: Coprocessor Increments
Anil,

I wasn't suggesting that you can't do what you're doing, but you end up running in to the risks which coprocessors are supposed to remove. The standard YMMV always applies.

You have a cluster… another team in your company wants to use the cluster. So instead of the cluster being a single resource for your app/team, it now becomes a shared resource. So now you have people accessing HBase for multiple apps.

You could then run multiple HBase HMasters with different locations for files, however… this can get messy.
HOYA seems to suggest this as the future.  If so, then you have to wonder about data locality.

Having your app update the primary table and then the secondary index is always a good fallback, however you need to ensure that you understand the risks.

With respect to secondary indexes… if you decouple the writes… you can get better throughput. Note that the code becomes a bit more complex because you're going to have to introduce a couple of different things.  But thats something for a different discussion…
On Oct 13, 2013, at 10:15 AM, anil gupta <[EMAIL PROTECTED]> wrote:

> Inline.
>
> On Sun, Oct 13, 2013 at 6:02 AM, Michael Segel <[EMAIL PROTECTED]>wrote:
>
>> Ok…
>>
>> Sure you can have your app update the secondary index table.
>> The only issue with that is if someone updates the base table outside of
>> your app,
>> they may or may not increment the secondary index.
>>
> Anil: We dont allow people to write data into HBase from their own HBase
> client. We control the writes into HBase. So, we dont have the problem of
> secondary index not getting written.
> For example, If you expose a restful web service you can easily control the
> writes to HBase. Even, if user requests to write one row in "main table",
> you application can have the logic to writing in "Secondary index" tables.
> In this way, it is transparent to users also. You can add/remove seconday
> indexes as you want.
>
>> Note that your secondary index doesn't have to be an inverted table, but
>> could be SOLR, LUCENE or something else.
>>
> Anil:As of now, we are happy with Inverted tables as they fit to our use
> case.
>
>>
>> So you really want to secondary indexes on the server.
>>
>> There are a couple of things that could improve the performance, although
>> the write to the secondary index would most likely lag under heavy load.
>>
>>
>> On Oct 12, 2013, at 11:27 PM, anil gupta <[EMAIL PROTECTED]> wrote:
>>
>>> John,
>>>
>>> My 2 cents:
>>> I tried implementing Secondary Index by using Region Observers on Put. It
>>> works well under low load. But, under heavy load the RO could not keep up
>>> with load cross region server writes.
>>> Then, i decided not to use RO as per Andrew's explanation and  I moved
>> all
>>> the logic of building secondary index tables on my HBase Client . Since
>>> then, the system has been running fine under heavy load.
>>> IMO, if you will use RO and do cross RS read/write then perhaps this will
>>> become your bottleneck in HBase.
>>> Is it possible for you to avoid RO and control the writes/updates from
>>> client side?
>>>
>>> Thanks,
>>> Anil Gupta
>>>
>>>
>>> On Fri, Oct 11, 2013 at 6:06 PM, John Weatherford <
>>> [EMAIL PROTECTED]> wrote:
>>>
>>>> OP Here :)
>>>>
>>>> Our current design involves a Region Observer on a table that does
>>>> increments on a second table. We took the approach that Michael said and
>>>> inside the RO, we got a new connection and everything. We believe this
>> is
>>>> causing deadlocks for us. Our next attempt is going to be writing to
>>>> another row in the same table where we will store the increments. If
>> this
>>>> doesn't work, we are going to simply pull the increments out of the RO
>> and
>>>> do them in the application or in Flume.
>>>>
>>>> @Tom Brown
>>>> I would be very interested to hear more about your solution of
>>>> aggregating the increments in another system that is then responsible
>> for
>>>> updating in Hbase.