Tuesday, November 5, 2013
Cassandra Last Night at the TRG
Cassandra was the topic at TRG last night.
That is to say, Apache Cassandra. I'm not clear why the project chose to refer to themselves by the name of a Greek prophetess who was doomed to always prophesying correctly, but also to never being believed.
Perhaps the the eventual consistency model?
Still, it doesn't seem like the greatest PR approach and it doesn't seem like the Big Data initiatives would like to think of their correct insights always being disregarded.
But such is the name of the product.
Our presenter, Adrian Rodriguez, did a nice hands-on tutorial where he built up a data model for a Social web application centered around dog photos. He provided a github account where the full blown application can be browsed.
He also pointed us to a very helpful consistency calculator website, where the implications of your consistency level choice are clearly shown: Cassandra Parameters for Dummies.
Adrian recommended the very sound policy of defining calls in quorum and then relaxing this only where necessary, in keeping with the dictum: "don't prematurely optimize."
I also liked his way of explaining that Cassandra databases grow out left to right, with everything attaching to the primary key as a new column, and with all the join overhead done upfront at update time in all the other relevant rows; in contrast to the Relational Model, where databases grow top to bottom as new rows are added. This is an excellent way for beginners to start wrapping their heads around this NoSql database.
Tonight is the Java Users group, so a report will be in order tomorrow on Groovy.
Full details of the presentation may be read here.