I wasn't really intending to describe a schema for a "webtable", but
rather coming up with a contrived example of a compound key where you
want to avoid hotspotting.
The point, which has been reiterated a few times, is that there is not
one solution for all row key requirements. Hashing/salting is just
another tool in the tool belt.
On 12/19/12 5:28 PM, Andrew Purtell wrote:
I generally agree. I built a webtable design once. We dropped the scheme
and reversed the domain to support "suffix glob" type queries over a group
of related hosts. There is then a natural hotspot at "com" but salting
would only have dispersed queries that should go to one row (or a group of
adjacent rows) over multiple regionservers, actually hurting query
efficiency. Instead we set the region split threshold low in the beginning,
under the assumption that the resulting splits in the keyspace from the
initial stream of URLs would approximate the overall distribution, then
turned up the split threshold when entering production steady state.
On Wed, Dec 19, 2012 at 2:15 PM, Nick Dimiduk <[email protected]> wrote:
On Wed, Dec 19, 2012 at 1:26 PM, David Arthur <[email protected]> wrote:
Let's say you want to decompose a url into domain and path to include in
your row key.
You could of course just use the url as the key, but you will see
hotspotting since most will start with "http".
Doesn't the original Bigtable paper [0] design around this problem by
dropping the protocol and only storing the domain? *goes to check* Yes, it
does.
Personally, I've never encountered an HBase schema design problem where
salting really nailed it. It's an okay place to start with initial designs,
especially if you don't know your data well. I'm a big fan of using the
natural variance in the data itself to solve this problem. OpenTSDB does
this quite well, IMHO. Plus, it's kind of a game or data puzzle -- how to
use the data's nature to your advantage :)
Just my 2ยข
-n
[0]:
http://static.googleusercontent.com/external_content/untrusted_dlcp/research.google.com/en/us/archive/bigtable-osdi06.pdf
