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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Pushing Cassandra 1.2 back a month to November?
Date Fri, 28 Sep 2012 19:42:27 GMT
All right.  With no dissenting opinions, let's make this the new plan of record.

I've created https://issues.apache.org/jira/browse/CASSANDRA-4734 for
the protocol change; let's get that into beta2 and take it from there.

On Wed, Sep 26, 2012 at 8:22 AM, Brandon Williams <driftx@gmail.com> wrote:
> +1
>
> The vnode troubleshooting process has been rough, so I'm all for more
> testing there.
>
> On Tue, Sep 25, 2012 at 12:16 PM, Jonathan Ellis <jbellis@gmail.com> wrote:
>> We are more or less on track for the promised late October 1.2 release
>> [1] but I'm starting to think we should expand the scope of 1.2 a bit
>> to get cql3 and the corresponding binary protocol truly "right."
>>
>> Specifically,
>> 1) We'd like to move the consistency level setting from the CQL
>> language to the protocol level.
>> 2) The binary protocol only really has a Java implementation so far.
>> Having the time to flesh out the Python implementation would be a good
>> sanity check before we commit to protocol stability.
>>
>> Additionally,
>> 3) vnodes is a big change that could use more time to test.  I'd like
>> to avoid a repeat of the schema change mess from 1.1, where we did a
>> substantial rewrite that took six minor releases to get all the bugs
>> out of.
>>
>> Gory details on the CQL situation:
>>
>> Currently, in CQL3, you set the consistency level of an operation in
>> the language, eg 'SELECT * FROM foo USING CONSISTENCY QUORUM'.  It now
>> looks like this was a mistake, and that consistency should be set at
>> the protocol level, i.e. as a separate parameter along with the query.
>>
>> The reasoning is that the CL applies to the guarantee provided by the
>> operation being successful, not to the query itself.  Specifically,
>> having the CL being part of the language means that CL is opaque to
>> low level client libraries without themselves parsing the CQL, which
>> we want to avoid.  Thus,
>>
>>     - Those libraries can't implement automatic retries policy, where a query
>>       would be retried with a smaller CL.  (I'm aware that this is often a
>>       Bad Idea, but it does have legitimate uses and not having that available
>>       is seen as a regression from the Thrift api.)
>>     - We had to introduce CASSANDRA-4448 to allow the client to configure some
>>       form of default CL since the library can't handle that anymore, which is
>>       hackish.
>>     - Executing prepared statements with different CL requires preparing
>>       multiple statements.
>>     - CL only makes sense for BATCH operations as a whole, not the
>>       sub-statements within the batch. Currently CQL3 "fixes" that by
>>       validating the given CLs match, but it would be much more clear
>>       if the CL was on the protocol side.
>>
>> Moving the CL to the protocol level solves all of that but the problem
>> is, if we move the CL from the language to the protocol after 1.2,
>> that's a breaking change of CQL3, so we're talking CQL4.  Bad idea.
>>
>> [1] although later-than-planned freeze is a warning sign
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of DataStax, the source for professional Cassandra support
>> http://www.datastax.com



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support
http://www.datastax.com

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