cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Alain RODRIGUEZ <arodr...@gmail.com>
Subject Re: Read Consistency
Date Tue, 23 Jun 2015 18:22:19 GMT
Hi,

I do not agree with Scenario 1 result Arun,

The 2 nodes don't have the data yet are available. IMHO what happens next i
a slow read since it will have to perform read repair and coordinator will
send back the result and an 'OK' message.Consistency is not met when nor
enough nodes were up.

Agreed on scenario 2. I would add that one repair will be synchronous and
mandatory while the second depends on your read repair chance parameter on
this table and is async.

C*heers

2015-06-23 20:16 GMT+02:00 Anuj Wadehra <anujw_2003@yahoo.co.in>:

> 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" <arunsirik@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_2003@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
>

Mime
View raw message