Thank you Biju ________________________________ From: Biju N <bijuatapa...@gmail.com> Sent: Wednesday, March 1, 2017 2:11:15 PM To: user@hbase.apache.org Subject: Re: On HBase Read Replicas
>From the table definition. For e.g. https://hbase.apache.org/apidocs/org/apache/hadoop/hbase/HTableDescriptor.html#getRegionReplication-- On Tue, Feb 28, 2017 at 3:30 PM, jeff saremi <jeffsar...@hotmail.com> wrote: > Enis > > just one more question. How would i go about getting the count of the > replica's for a table or columngroup? thanks > > ________________________________ > From: Enis Söztutar <enis....@gmail.com> > Sent: Wednesday, February 22, 2017 1:38:41 PM > To: hbase-user > Subject: Re: On HBase Read Replicas > > If you are doing a get to a specific replica, it will execute as a read > with retries to a single "copy". There will not be any backup / fallback > RPCs to any other replica. > > Only in timeline consistency mode there will be fallback RPCs. > > Enis > > On Sun, Feb 19, 2017 at 9:43 PM, Anoop John <anoop.hb...@gmail.com> wrote: > > > 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 > > >> > >>> > > >> > > > >> > > >
