Hi Anuj, That could indeed explain reads on my new DC. However, what I'm seeing in my client application is that every now and then, a read query does not produce any result, while I'm sure that it should. If I understand the read repair process correctly, it will never cause a read query fail to find a replica, right?
On Tue, Sep 8, 2015 at 4:40 AM, Anuj Wadehra <anujw_2...@yahoo.co.in> wrote: > Hi Tom, > > While reading data ( even at CL LOCAL_QUORUM), if data in different nodes > required to meet CL in your local cluster doesnt match, data will be read > from remote dc for read repair if read_repair_chance is not 0. > > Imp points: > 1.If you are reading and writing at local_quorum you can set > read_repair_chance to 0 to prevent cross dc read repair. > 2. For enabling dc local read repairs you can use > dclocal_read_repair_chance and set read_repair_chance to 0. > 3. If you are experiencing frequent requests being routed due to digest > mismatch you may need to investigate mutation drops in your cluster using > tpstats. > > Refer to similar issue raised by us : > https://issues.apache.org/jira/browse/CASSANDRA-8479 > > Thanks > Anuj > > Sent from Yahoo Mail on Android > <https://overview.mail.yahoo.com/mobile/?.src=Android> > ------------------------------ > *From*:"Tom van den Berge" <t...@drillster.com> > *Date*:Tue, 8 Sep, 2015 at 1:31 am > *Subject*:Re: How to prevent queries being routed to new DC? > > NetworkTopologyStrategy > > On Mon, Sep 7, 2015 at 4:39 PM, Ryan Svihla <r...@foundev.pro> wrote: > >> What's your keyspace replication strategy? >> >> On Thu, Sep 3, 2015 at 3:16 PM Tom van den Berge < >> tom.vandenbe...@gmail.com> wrote: >> >>> Thanks for your help so far! >>> >>> I have some problems trying to understand the jira mentioned by Rob :( >>> >>> I'm currently trying to set up the first node in the new DC with >>> auto_bootstrap = true. The node then becomes visible with status "joining", >>> which (hopefully) prevents other DCs from sending queries to it. >>> >>> Do you think this will work? >>> >>> >>> >>> On Thu, Sep 3, 2015 at 9:46 PM, Robert Coli <rc...@eventbrite.com> >>> wrote: >>> >>>> On Thu, Sep 3, 2015 at 12:25 PM, Bryan Cheng <br...@blockcypher.com> >>>> wrote: >>>> >>>>> I'd recommend you enable tracing and do a few queries in a controlled >>>>> environment to verify that queries are being routed to your new nodes. >>>>> Provided you have followed the procedure outlined above (specifically, >>>>> have >>>>> set auto_bootstrap to false in your new cluster), rebuild has not been >>>>> run, >>>>> the application is not connecting to the new cluster, and all your queries >>>>> are run at LOCAL_* quorum levels, I do not believe those queries should be >>>>> routed to the new dc. >>>>> >>>> >>>> Other than CASSANDRA-9753, this is true. >>>> >>>> https://issues.apache.org/jira/browse/CASSANDRA-9753 (Unresolved; ): >>>> "LOCAL_QUORUM reads can block cross-DC if there is a digest mismatch" >>>> >>>> =Rob >>>> >>>> >>> -- >> Regards, >> >> Ryan Svihla > > > > > -- > Tom van den Berge > Lead Software Engineer > [image: Drillster] Middenburcht 136 > 3452 MT Vleuten > Netherlands+31 30 755 53 30 > www.drillster.com [image: Follow us on Facebook] Follow us on Facebook > <https://www.facebook.com/Drillster> >
