Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
HBase, mail # user - Coprocessor Increments


Copy link to this message
-
Re: Coprocessor Increments
Michael Segel 2013-10-15, 18:12
Anil,
> Agree with you. But, as per my knowledge and experience with coprocessors,
> they are meant to be used for operations that are local to RS. Otherwise,
> you are in danger of running into deadlocks, scalability issues.
I also did a quick look at…  HBASE-7474…

You start with the assumption that all of your data is within a single region.

IMHO, this is a very narrow window for use cases.

Most use cases have data that crosses region boundaries.

From a design perspective… limiting the use case to only within region… kinda kills the reason for coprocessors to exist. Even looking back at the implementation by Google, they don't appear to have this problem… errr limitation.

Sorry… IMHO and YMMV.
On Oct 14, 2013, at 3:25 PM, anil gupta <[EMAIL PROTECTED]> wrote:

> Inline.
>
>
> On Mon, Oct 14, 2013 at 7:50 AM, Michael Segel <[EMAIL PROTECTED]>wrote:
>
>> 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.
>>
> Agree with you. But, as per my knowledge and experience with coprocessors,
> they are meant to be used for operations that are local to RS. Otherwise,
> you are in danger of running into deadlocks, scalability issues.
>
>>
>> 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.
>>
> Well, its a separation of responsibility in this case. We don't want teams
> to step each other toes and at the same time work well as an ecosystem.
> Rule: Other teams can use same cluster. But they cannot write directly into
> the tables that we own/control.  If they want to write into our tables then
> they have to use our HBase Client.
>
>>
>> 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.
>>
> HOYA is not even in beta at present. So, right now we are not thinking
> about it.
>
>>
>> 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.
>>
> Agree, i understand that there is risk. But, you have to bite the bullet
> when you are doing something that is not supported out of the box.  We also
> use CP's wherever they are appropriate(like HBASE-7474).
>
>>
>> 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…
>>
> Whether to use CP or not, depends on the use case. In my opinion, CP's are
> really powerful and an awesome feature in HBase. But, sometimes if not used
> properly(like creating a Cyclic Graph as per Tom's example), they might be
> problematic.
>
>
>>
>> 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"