Short of actually making ConsistencyLevel pluggable or adding/changing one
of the existing levels, an alternative approach would be to divide up the
cluster into either real or pseudo-datacenters (with RF=2 in each DC), and
then write with QUORUM (which would be 3 nodes, across any combination of
d
Firstly, this situation only occurs if you need strong consistency and are
using an even replication factor (RF4, RF6, etc).
Secondly, either the read or write still need to be performed at a minimum
level of QUORUM. This means there are no extra availability benefits from
your proposal (i.e. a min
Would love to see real pluggable consistency levels. Sorta sad it got
wont-fixed - may be time to revisit that, perhaps it's more feasible now.
https://issues.apache.org/jira/browse/CASSANDRA-8119 is also semi-related,
but a different approach (CL-as-UDF)
On Thu, Jun 8, 2017 at 9:26 PM, Brandon W
I don't disagree with you there and have never liked TWO/THREE. This is
somewhat relevant: https://issues.apache.org/jira/browse/CASSANDRA-2338
I don't think going to CL.FOUR, etc, is a good long-term solution, but I'm
also not sure what is.
On Thu, Jun 8, 2017 at 11:20 PM, Dikang Gu wrote:
>
To me, CL.TWO and CL.THREE are more like work around of the problem, for
example, they do not work if the number of replicas go to 8, which does
possible in our environment (2 replicas in each of 4 DCs).
What people want from quorum is strong consistency guarantee, as long as
R+W > N, there are th
> So, for the quorum, what we really want is that there is one overlap among
> the nodes in write path and read path. It actually was my assumption for a
> long time that we need (N/2 + 1) for write and just need (N/2) for read,
> because it's enough to provide the strong consistency.
>
You are wr
>
>
> So, for the quorum, what we really want is that there is one overlap among
>> the nodes in write path and read path. It actually was my assumption for a
>> long time that we need (N/2 + 1) for write and just need (N/2) for read,
>> because it's enough to provide the strong consistency.
>>
>
>
> We have CL.TWO.
>
>
>
This was actually the original motivation for CL.TWO and CL.THREE if memory
serves:
https://issues.apache.org/jira/browse/CASSANDRA-2013
We have CL.TWO.
On Thu, Jun 8, 2017 at 10:03 PM, Dikang Gu wrote:
> So, for the quorum, what we really want is that there is one overlap among
> the nodes in write path and read path. It actually was my assumption for a
> long time that we need (N/2 + 1) for write and just need (N/2) for read,
>
So, for the quorum, what we really want is that there is one overlap among
the nodes in write path and read path. It actually was my assumption for a
long time that we need (N/2 + 1) for write and just need (N/2) for read,
because it's enough to provide the strong consistency.
On Thu, Jun 8, 2017
It would be a little weird to change the definition of QUORUM, which means
majority, to mean something other than majority for a single use case.
Sounds like you want to introduce a new CL, HALF.
On Thu, Jun 8, 2017 at 7:43 PM Dikang Gu wrote:
> Justin, what I suggest is that for QUORUM consisten
Justin, what I suggest is that for QUORUM consistent level, the block for
write should be (num_replica/2)+1, this is same as today, but for read
request, we just need to access (num_replica/2) nodes, which should provide
enough strong consistency.
Dikang.
On Thu, Jun 8, 2017 at 7:38 PM, Justin Ca
2/4 for write and 2/4 for read would not be sufficient to achieve strong
consistency, as there is no overlap.
In your particular case you could potentially use QUORUM for write and TWO
for read (or vice-versa) and still achieve strong consistency. If you add
additional nodes in the future this wou
Hello there,
We have some use cases are doing consistent read/write requests, and we
have 4 replicas in that cluster, according to our setup.
What's interesting to me is that, for both read and write quorum requests,
they are blocked for 4/2+1 = 3 replicas, so we are accessing 3 (for write)
+ 3 (
Python recently made a switch to Github, and I was an interested onlooker. One
thing I found relevant to Cassandra was a new tool added by Larry Hastings,
called blurb (https://github.com/larryhastings/blurb):
> blurb is a tool designed to rid CPython core development of the scourge of
> Misc/N
Hi all
As part of my MSc project, I've done a new compaction strategy for
Cassandra, called Burst Hour Compaction Strategy. You can find the JIRA
ticket here: https://issues.apache.org/jira/browse/CASSANDRA-12201
In a nutshell, the background compaction for this strategy is only
triggered during
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