Thanks Enis.. I was not knowing the way of setting replica id
specifically.. So what will happen if that said replica is down at
the read time? Will that go to another replica?
-Anoop-
On Sat, Feb 18, 2017 at 3:34 AM, Enis Söztutar <enis....@gmail.com> wrote:
> You can do gets using two different "modes":
> - Do a read with backup RPCs. In case, the algorithm that I have above
> will be used. 1 RPC to primary, and 2 more RPCs after primary timeouts.
> - Do a read to a single replica. In this case, there is only 1 RPC that
> will happen to that given replica.
>
> Enis
>
> On Fri, Feb 17, 2017 at 12:03 PM, jeff saremi <jeffsar...@hotmail.com>
> wrote:
>
>> Enis
>>
>> Thanks for taking the time to reply
>>
>> So i thought that a read request is sent to all Replicas regardless. If we
>> have the option of Sending to one, analyzing response, and then sending to
>> another, this bodes well with our scenarios.
>>
>> Please confirm
>>
>> thanks
>>
>> ________________________________
>> From: Enis Söztutar <enis....@gmail.com>
>> Sent: Friday, February 17, 2017 11:38:42 AM
>> To: hbase-user
>> Subject: Re: On HBase Read Replicas
>>
>> You can use read-replicas to distribute the read-load if you are fine with
>> stale reads. The read replicas normally have a "backup rpc" path, which
>> implements a logic like this:
>> - Send the RPC to the primary replica
>> - if no response for 100ms (or configured timeout), send RPCs to the other
>> replicas
>> - return the first non-exception response.
>>
>> However, there is also another feature for read replicas, where you can
>> indicate which exact replica_id you want to read from when you are doing a
>> get. If you do this:
>> Get get = new Get(row);
>> get.setReplicaId(2);
>>
>> the Get RPC will only go to the replica_id=2. Note that if you have region
>> replication = 3, then you will have regions with replica ids: {0, 1, 2}
>> where replica_id=0 is the primary.
>>
>> So you can do load-balancing with a get.setReplicaId(random() %
>> num_replicas) kind of pattern.
>>
>> Enis
>>
>>
>>
>> On Thu, Feb 16, 2017 at 9:41 AM, Anoop John <anoop.hb...@gmail.com> wrote:
>>
>> > Never saw this kind of discussion.
>> >
>> > -Anoop-
>> >
>> > On Thu, Feb 16, 2017 at 10:13 PM, jeff saremi <jeffsar...@hotmail.com>
>> > wrote:
>> > > Thanks Anoop.
>> > >
>> > > Understood.
>> > >
>> > > Have there been enhancement requests or discussions on load balancing
>> by
>> > providing additional replicas in the past? Has anyone else come up with
>> > anything on this?
>> > > thanks
>> > >
>> > > ________________________________
>> > > From: Anoop John <anoop.hb...@gmail.com>
>> > > Sent: Thursday, February 16, 2017 2:35:48 AM
>> > > To: user@hbase.apache.org
>> > > Subject: Re: On HBase Read Replicas
>> > >
>> > > The region replica feature came in so as to reduce the MTTR and so
>> > > increase the data availability. When the master region containing RS
>> > > dies, the clients can read from the secondary regions. But to keep
>> > > one thing in mind that this data from secondary regions will be bit
>> > > out of sync as the replica is eventual consistent. Because of this
>> > > said reason, change client so as to share the load across diff RSs
>> > > might be tough.
>> > >
>> > > -Anoop-
>> > >
>> > > On Sun, Feb 12, 2017 at 8:13 AM, jeff saremi <jeffsar...@hotmail.com>
>> > wrote:
>> > >> Yes indeed. thank you very much Ted
>> > >>
>> > >> ________________________________
>> > >> From: Ted Yu <yuzhih...@gmail.com>
>> > >> Sent: Saturday, February 11, 2017 3:40:50 PM
>> > >> To: user@hbase.apache.org
>> > >> Subject: Re: On HBase Read Replicas
>> > >>
>> > >> Please take a look at the design doc attached to
>> > >> https://issues.apache.org/jira/browse/HBASE-10070.
>> > >>
>> > >> Your first question would be answered by that document.
>> > >>
>> > >> Cheers
>> > >>
>> > >> On Sat, Feb 11, 2017 at 2:06 PM, jeff saremi <jeffsar...@hotmail.com>
>> > wrote:
>> > >>
>> > >>> The first time I heard replicas in HBase the following thought
>> > immediately
>> > >>> came to my mind:
>> > >>> To alleviate the load in read-heavy clusters, one could assign Region
>> > >>> servers to be replicas of others so that the load is distributed and
>> > there
>> > >>> is less pressure on the main RS.
>> > >>>
>> > >>> Just 2 days ago a colleague quoted a paragraph from HBase manual that
>> > >>> contradicted this completely. Apparently, the replicas do not help
>> > with the
>> > >>> load but they actually contribute to more traffic on the network and
>> > on the
>> > >>> underlying file system
>> > >>>
>> > >>> Would someone be able to give us some insight on why anyone would
>> want
>> > >>> replicas?
>> > >>>
>> > >>> And also could one easily change this behavior in the HBase native
>> Java
>> > >>> client to support what I had been imagining as the concept for
>> > replicas?
>> > >>>
>> > >>>
>> > >>> thanks
>> > >>>
>> >
>>
