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From Paul Prescod <pres...@gmail.com>
Subject ConsistencyLevel.ZERO
Date Wed, 07 Apr 2010 16:02:40 GMT
On Tue, Apr 6, 2010 at 10:58 AM, Tatu Saloranta <tsaloranta@gmail.com> wrote:
> On Tue, Apr 6, 2010 at 8:17 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>> On Tue, Apr 6, 2010 at 2:13 AM, Ilya Maykov <ivmaykov@gmail.com> wrote:
>>> That does sound similar. It's possible that the difference I'm seeing
>>> between ConsistencyLevel.ZERO and ConsistencyLevel.ALL is simply due
>>> to the fact that using ALL slows down the writers enough that the GC
>>> can keep up.
>>
>> No, it's mostly due to ZERO meaning "buffer this locally and write it
>> when it's convenient," and buffering takes memory.  If you check your
>> tpstats you will see the pending ops through the roof on the node
>> handling the thrift connections.
>
> This sounds like a great FAQ entry? (apologies if it's already included)
> So that ideally users would only use this setting if they (think they)
> know what they are doing. :-)

I added this note to the API docs:

 * ConsistencyLevel.ZERO: Ensure nothing. A write happens
asynchronously in background. If too many of these queue up, buffers
will explode and bad things will happen.

Apologies if I violated any community conventions. I'm happy to fix
the text if someone has a better suggestion.

 Paul Prescod

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