Sorry. I have to jump in and disagree. Data is not guaranteed to retire in scenario 1. Since two nodes do not have data and two nodes may be the only nodes queried at that CL, the read query may return data or not.
Similarly, in scenario 2, the query may not return the most recent data because the node with that data may not be queried at all (the other two may). Keep in mind, these scenarios seem to generally assume you are not writing data at consistently at QUORUM CL so therefore your reads may be inconsistent. On Tuesday, June 23, 2015, Anuj Wadehra <anujw_2...@yahoo.co.in> wrote: > Thanks..So all of us agree that in scenario 1, data would be returned and > that was my initial understanding.. > > > Anuj > > > > Sent from Yahoo Mail on Android > <https://overview.mail.yahoo.com/mobile/?.src=Android> > ------------------------------ > *From*:"Anuj Wadehra" <anujw_2...@yahoo.co.in > <javascript:_e(%7B%7D,'cvml','anujw_2...@yahoo.co.in');>> > *Date*:Wed, 24 Jun, 2015 at 12:15 am > *Subject*:Re: Read Consistency > > M more confused...Different responses. .Anyone who can explain with 100% > surity ? > > Thanks > Anuj > > > Sent from Yahoo Mail on Android > <https://overview.mail.yahoo.com/mobile/?.src=Android> > ------------------------------ > *From*:"arun sirimalla" <arunsi...@gmail.com > <javascript:_e(%7B%7D,'cvml','arunsi...@gmail.com');>> > *Date*:Wed, 24 Jun, 2015 at 12:00 am > *Subject*:Re: Read Consistency > > > Thanks good to know that. > > On Tue, Jun 23, 2015 at 11:27 AM, Philip Thompson < > philip.thomp...@datastax.com> wrote: > >> Yes, that is what he means. CL is for how many nodes need to respond, not >> agree. >> >> On Tue, Jun 23, 2015 at 2:26 PM, arun sirimalla <arunsi...@gmail.com> >> wrote: >> >>> So do you mean with CL set to QUORUM, if data is only on one node, the >>> query still succeeds. >>> >>> On Tue, Jun 23, 2015 at 11:21 AM, Philip Thompson < >>> philip.thomp...@datastax.com> wrote: >>> >>>> Anuj, >>>> >>>> In the first scenario, the data from the single node holding data is >>>> returned. The query will not fail if the consistency level is met, even if >>>> the read was inconsistent. >>>> >>>> On Tue, Jun 23, 2015 at 2:16 PM, Anuj Wadehra <anujw_2...@yahoo.co.in> >>>> wrote: >>>> >>>>> Why would it fail and with what Thrift error? What if the data didnt >>>>> exist on any of the nodes..query wont fail if doesnt find data.. >>>>> >>>>> Not convinced.. >>>>> >>>>> Sent from Yahoo Mail on Android >>>>> <https://overview.mail.yahoo.com/mobile/?.src=Android> >>>>> ------------------------------ >>>>> *From*:"arun sirimalla" <arunsi...@gmail.com> >>>>> *Date*:Tue, 23 Jun, 2015 at 11:39 pm >>>>> *Subject*:Re: Read Consistency >>>>> >>>>> Scenario 1: Read query is fired for a key, data is found on one node >>>>> and not found on other two nodes who are responsible for the token >>>>> corresponding to key. >>>>> >>>>> You read query will fail, as it expects to receive data from 2 nodes >>>>> with RF=3 >>>>> >>>>> >>>>> Scenario 2: Read query is fired and all 3 replicas have different data >>>>> with different timestamps. >>>>> >>>>> Read query will return the data with most recent timestamp and trigger >>>>> a read repair in the backend . >>>>> >>>>> On Tue, Jun 23, 2015 at 10:57 AM, Anuj Wadehra <anujw_2...@yahoo.co.in >>>>> > wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> Need to validate my understanding.. >>>>>> >>>>>> RF=3 , Read CL = Quorum >>>>>> >>>>>> What would be returned to the client in following scenarios: >>>>>> >>>>>> Scenario 1: Read query is fired for a key, data is found on one node >>>>>> and not found on other two nodes who are responsible for the token >>>>>> corresponding to key. >>>>>> >>>>>> Options: no data is returned OR data from the only node having data >>>>>> is returned? >>>>>> >>>>>> Scenario 2: Read query is fired and all 3 replicas have different >>>>>> data with different timestamps. >>>>>> >>>>>> Options: data with latest timestamp is returned OR something else??? >>>>>> >>>>>> Thanks >>>>>> Anuj >>>>>> >>>>>> Sent from Yahoo Mail on Android >>>>>> <https://overview.mail.yahoo.com/mobile/?.src=Android> >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> Arun >>>>> >>>> >>>> >>> >>> >>> -- >>> Arun >>> Senior Hadoop/Cassandra Engineer >>> Cloudwick >>> >>> >>> 2014 Data Impact Award Winner (Cloudera) >>> >>> http://www.cloudera.com/content/cloudera/en/campaign/data-impact-awards.html >>> >>> >> > > > -- > Arun > Senior Hadoop/Cassandra Engineer > Cloudwick > > > 2014 Data Impact Award Winner (Cloudera) > > http://www.cloudera.com/content/cloudera/en/campaign/data-impact-awards.html > >
