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From AJ ...@dude.podzone.net>
Subject Re: Concurrency: Does C* support a Happened-Before relation between processes' writes?
Date Sat, 25 Jun 2011 20:15:22 GMT
On 6/25/2011 8:24 AM, Edward Capriolo wrote:
> I played around with the bakery algorithm and had ok success the
> challenges are most implementations assume an n size array of fixed
> clients and when you get it working it turns out to be a good number
> of cassandra ops to acquire your bakery lock.
>

I was thinking rather than making certain that there is a column 
reserved for each node and having to keep it updated, you can just over 
allocate a large number that would always be enough, like 100.  A slice 
of 100 byte-sized values shouldn't be a significant perf hit vs 3 or 4.  
If you only have 3 nodes in your cluster and the last 97 go unused, that 
would be ok; it would be as if those non-existent "customers" never take 
a number.

For optimizing for C*, I think you can get away with minimal getSlices 
for the loops.  If you're lucky, you can fall through all of them using 
the results from only 1 getSlice.  Only if a process is "entering" or 
has a higher priority number will you need to wait and then do another 
getSlice and only a slice for the remaining columns.  I think my logic 
is correct; do you agree?

Did you have other problems other than performance?

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