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From Jake Luciani <jak...@gmail.com>
Subject Re: Migrating all rows from 0.6.13 to 0.7.5 over thrift?
Date Sat, 07 May 2011 20:35:30 GMT
I know thrift and python and Unicode don't mix. 

 

On May 7, 2011, at 4:21 PM, aaron morton <aaron@thelastpickle.com> wrote:

> I've been able to reproduce the fault using python on my mac book see 
> https://github.com/amorton/cassandra-unicode-bug
> 
> When we try to find the unicode key in the index in 0.7 it fails because the tokens are
different. The readme in the github project has more info. 
> 
> Any thoughts?  Will try to find some more time to keep digging. 
> 
> Aaron
> 
> 
> On 7 May 2011, at 20:44, aaron morton wrote:
> 
>> get_range_slices() does read repair if enabled (checked DoConsistencyChecksBoolean
in the config, it's on by default) so you should be getting good reads. If you want belt-and-braces
run nodetool repair first. 
>> 
>> Hope that helps.
>> 
>> 
>> On 7 May 2011, at 11:46, Jeremy Hanna wrote:
>> 
>>> Great!  I just wanted to make sure you were getting the information you needed.
>>> 
>>> On May 6, 2011, at 6:42 PM, Henrik Schröder wrote:
>>> 
>>>> Well, I already completed the migration program. Using get_range_slices I
could migrate a few thousand rows per second, which means that migrating all of our data would
take a few minutes, and we'll end up with pristine datafiles for the new cluster. Problem
solved!
>>>> 
>>>> I'll see if I can create datafiles in 0.6 that are uncleanable in 0.7 so
that you all can repeat this and hopefully fix it.
>>>> 
>>>> 
>>>> /Henrik Schröder
>>>> 
>>>> On Sat, May 7, 2011 at 00:35, Jeremy Hanna <jeremy.hanna1234@gmail.com>
wrote:
>>>> If you're able, go into the #cassandra channel on freenode (IRC) and talk
to driftx or jbellis or aaron_morton about your problem.  It could be that you don't have
to do all of this based on a conversation there.
>>>> 
>>>> On May 6, 2011, at 5:04 AM, Henrik Schröder wrote:
>>>> 
>>>>> I'll see if I can make some example broken files this weekend.
>>>>> 
>>>>> 
>>>>> /Henrik Schröder
>>>>> 
>>>>> On Fri, May 6, 2011 at 02:10, aaron morton <aaron@thelastpickle.com>
wrote:
>>>>> The difficulty is the different thrift clients between 0.6 and 0.7.
>>>>> 
>>>>> If you want to roll your own solution I would consider:
>>>>> - write an app to talk to 0.6 and pull out the data using keys from the
other system (so you know can check referential integrity while you are at it). Dump the data
to flat file.
>>>>> - write an app to talk to 0.7 to load the data back in.
>>>>> 
>>>>> I've not given up digging on your migration problem, having to manually
dump and reload if you've done nothing wrong is not the best solution. I'll try to find some
time this weekend to test with:
>>>>> 
>>>>> - 0.6 server, random paritioner, standard CF's, byte column
>>>>> - load with python or the cli on osx or ubuntu (dont have a window machine
any more)
>>>>> - migrate and see whats going on.
>>>>> 
>>>>> If you can spare some sample data to load please send it over in the
user group or my email address.
>>>>> 
>>>>> Cheers
>>>>> 
>>>>> -----------------
>>>>> Aaron Morton
>>>>> Freelance Cassandra Developer
>>>>> @aaronmorton
>>>>> http://www.thelastpickle.com
>>>>> 
>>>>> On 6 May 2011, at 05:52, Henrik Schröder wrote:
>>>>> 
>>>>>> We can't do a straight upgrade from 0.6.13 to 0.7.5 because we have
rows stored that have unicode keys, and Cassandra 0.7.5 thinks those rows in the sstables
are corrupt, and it seems impossible to clean it up without losing data.
>>>>>> 
>>>>>> However, we can still read all rows perfectly via thrift so we are
now looking at building a simple tool that will copy all rows from our 0.6.3 cluster to a
parallell 0.7.5 cluster. Our question is now how to do that and ensure that we actually get
all rows migrated? It's a pretty small cluster, 3 machines, a single keyspace, a singke columnfamily,
~2 million rows, a few GB of data, and a replication factor of 3.
>>>>>> 
>>>>>> So what's the best way? Call get_range_slices and move through the
entire token space? We also have all row keys in a secondary system, would it be better to
use that and make calls to get_multi or get_multi_slices instead? Are we correct in assuming
that if we use the consistencylevel ALL we'll get all rows?
>>>>>> 
>>>>>> 
>>>>>> /Henrik Schröder
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>> 
> 

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