
ComDB2: Bloomberg’s Highly Available Relational Database System [pdf] - irfansharif
http://www.vldb.org/pvldb/vol9/p1377-scotti.pdf
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elvinyung
There's too many databases that abbreviate to CDB :P

This is interesting, but the weird thing is that I'm not sure this is all that
different from e.g. hand sharding at the application level. By that I mean
that ComDB2 doesn't seem to provide a real way of seamlessly sharding your
data. Near the end of the paper:

> Under our design, each portion of the table has its own master (getting many
> of the benefits of a multi-master system) and is able to write to the
> portion it owns without coordinating with partitions uninvolved in the
> transaction.

Maybe the paper is missing some details on how queries and transactions are
coordinated between masters, but it seems to imply that the application level
has to handle this kind of stuff.

~~~
irfansharif
The section you're referring to is the work underway to increase write
performance, which is currently bounded by the master node's ability to
process bplogs (an internal structure used to detect write-write conflicts).

re: 'the application level has to handle [sharding]', the table partitioning
described in this section is merely a conceptual model 'assigning' masters to
what are presumably non-overlapping row ranges in order to increase write
throughput (writes/reads will be processed via that specific master). The
behaviour of the system still resembles a single node database, this is
alluded to intermittently throughout.

(also CRDB is the preferred acronym for CockroachDB haha, source: interning
there)

~~~
elvinyung
> The behaviour of the system still resembles a single node database, this is
> alluded to intermittently throughout.

The impression that I get from reading the paper is that this is only true as
long as the interaction involves only a single master. Or at the very least,
situations where the working set has to be sharded among multiple masters are
not described in any detail.

~~~
alexjscotti
Alex Scotti here. Sharding isn't something we dealt with. As the paper
suggested, there was 'work in progress.'

~~~
elvinyung
I see -- thanks!

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cwyers
At the end of the paper they say they look forward to releasing it under an
open source license. That's really interesting.

~~~
elvinyung
In the first page, there's a footnote that says:

> Comdb2 will be published under an open source license in 2016

which does not seem to be true.

~~~
irfansharif
I spoke to Mark Hannum (one of the authors of the paper) recently, it's slated
for a release in either this quarter or the next.

~~~
elvinyung
Ah, cool!

