NoSQL

In April 2010, Google updated its indexing system. Caffeine - the name of this project - was pretty transparent for the large public but represents an in depth change for Google. It does not directly improve the search page, like instant search, but the indexing mechanism, the way to provide pertinent search results. For the end user, this change allows reducing the delay between when a page is founded and when it is made available in the Google search. Google has recently published a research…

In the first part, I described the potential interest of using Hadoop for Value At Risk calculation in order to analyze intermediate results. In the three (2,3, 4) next parts I have detailled how to implement the VAR calculation with Hadoop. Then in the fifth part, I have studied how to analyse the intermediate results with Hive. I will finally give you now some performance figures on Hadoop and compare them with GridGain ones. According to those figures, I will detail some performance key points…

In the first part of this series, I have introduced why Hadoop framework could be useful to compute the VAR and analyze intermediate values. In the second part and third part and fourth part I have given two concrete implementations of VAR calculation with Hadoop with optimizations. Another interest of using Hadoop for Value At Risk calculation is the ability to analyse the intermediate values inside Hadoop through Hive. This is the goal of this (smaller) part of this series.

HDFS stores huge amount of data but storing it is worthless if you cannot analyse it and obtain information. Option #1 : Hadoop : the Map/Reduce engine Hadoop Overview Hadoop is a Map/Reduce framework that works on HDFS or on HBase. The main idea is to decompose a job into several and identical tasks that can be executed closer to the data (on the DataNode). In addition, each task is parallelized : the Map phase. Then all these intermediate results are merged into one result…

Hadoop Distributed File System can be considered as a standard file system butt it is distributed. So from the client point of view, he sees a standard file system (the one he can have on your laptop) but behind this, the file system actually runs on several machines. Thus, HDFS implements fail-over using data replication and has been designed to manipulate, store large data sets (in large file) in a write-one-read-many access model for files.

I saw the talks of Greg Young about CQRS & especially “Event Sourcing” a couple of times and each time, I really really tell myself this pattern is just “génial” (the way we say it in french) even if Martin Fowler wrote about it in 2005 and deals in details with implementation concerns and issues (especially in the cases of integration with external systems). Event Sourcing : stop thinking of your datas as a stock but rather as a list of events...