The first release (0.19.0) from the 0.19 branch of Apache Hadoop Core was made on November 24. Many changes go into a release like this, and it can be difficult to get a feel for the more significant ones, even with the detailed Jira log, change log, and release notes. (There’s also JDiff documentation, which is a great way to see how the public API changed,
(guest blog post by Matei Zaharia)
When Apache Hadoop started out, it was designed mainly for running large batch jobs such as web indexing and log mining. Users submitted jobs to a queue, and the cluster ran them in order. However, as organizations placed more data in their Hadoop clusters and developed more computations they wanted to run, another use case became attractive: sharing a MapReduce cluster between multiple users.
We’re happy to announce a new tool we have been developing here at Cloudera: Hadoop Development Status. Hadoop Development Status aims to help the Hadoop community understand its direction, health, and participants. The project currently monitors the most active contributors according to mailing list traffic, the most watched JIRA tickets, and aggregate traffic volumes on the Hadoop mailing lists.
The graph of messages per month on the Hadoop Core lists shows a sustained growth in traffic.
It is common for a MapReduce program to require one or more files to be read by each map or reduce task before execution. For example, you may have a lookup table that needs to be parsed before processing a set of records. To address this scenario, Hadoop’s MapReduce implementation includes a distributed file cache that will manage copying your file(s) out to the task execution nodes.
The DistributedCache was introduced in Hadoop 0.7.0;
Apache Hadoop exists within a rich ecosystem of tools for processing and analyzing large data sets. At Facebook, my previous employer, we contributed a few projects of note to this ecosystem, all under the Apache 2.0 license:
- Thrift: A cross-language RPC framework that powers many of Facebook’s services, include search, ads, and chat. Among other things, Thrift defines a compact binary serialization format that is often used to persist data structures for later analysis.