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From "Han,Meng" <>
Subject Re: How to extract information from commit log?
Date Tue, 18 Mar 2014 19:32:13 GMT

Hi Jonathan, 

Thank you for the timely reply. I am doing this
experiment on a continuous basis. To be more specific, I will issue a
large amount of read and write operations to a particular key in a short
time interval. I'd like to know the order that write operations happens
at each replica. TImestamps definitely help to determine order, but the
WRITETIME and SStable2Json both looks me only return the timestamps when
that key was updated the moment the WRITETIME/SStable2Json is issued. It
looks like a one time thing to me. Or put in another way, if I want to
get the write time for all write operations in that short invertal to
determine a total order for write on that replia I have to constantly
issue WRITETIME to this replica? Correct me if I am wrong here. 

me up pleeeeeeeeeease! 

On Tue, 18 Mar 2014 15:05:07 -0400, Jonathan
Lacefield wrote: 

> Hello, 
> Is this a one time investigative item or
are you looking to set something up to do this continuously? Don't
recommend trying to read the commit log. 
> You can always use the
WRITETIME function in CQL or look within SSTables via the SStable2Json
utility to see write times for particular versions of partitions. 
> Jonathan Lacefield 
> Solutions Architect, DataStax 
(404) 822 3487 
> [1] 
> [2] 
> On Tue, Mar 18, 2014 at 2:25 PM,
Han,Meng wrote:
>> Hi Cassandra hackers!
>> I have a question
regarding extracting useful information from commit log.
>> Since
its a binary log, how should I extract information such as timestamp,
values from it? Does anyone know any binary log reader that I can use
directly to read commit log?
>> If there is no such reader, could
someone give me some advice hwo I can wrote such a reader?
Particularly, I want to know the order that write operations happens at
each replica(cassandra server node) along with their timestamps, Does
anyone know other methods how I can get this information without
instrumenting Cassandra code?
>> Any help is appreciated!
>> Meng



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