This JIRA incorporates adding a new file system implementation for accessing Windows Azure Storage - Blob from within Hadoop, such as using blobs as input to MR jobs or configuring MR jobs to put their output directly into blob storage.
At a high level, the code here extends the FileSystem class to provide an implementation for accessing blob storage; the scheme wasb is used for accessing it over HTTP, and wasbs for accessing over HTTPS. We use the URI scheme:
to address individual blobs. We use the standard Azure Java SDK (com.microsoft.windowsazure) to do most of the work. In order to map a hierarchical file system over the flat name-value pair nature of blob storage, we create a specially tagged blob named path/to/dir whenever we create a directory called path/to/dir, then files under that are stored as normal blobs path/to/dir/file. We have many metrics implemented for it using the Metrics2 interface. Tests are implemented mostly using a mock implementation for the Azure SDK functionality, with an option to test against a real blob storage if configured (instructions provided inside in README.txt).
This has been ongoing work for a while, and the early version of this work can be seen in
HADOOP-8079. This JIRA is a significant revision of that and we'll post the patch here for Hadoop trunk first, then post a patch for branch-1 as well for backporting the functionality if accepted. Credit for this work goes to the early team: Min Wei, David Lao, Lengning Liu and Alexander Stojanovic as well as multiple people who have taken over this work since then (hope I don't forget anyone): Dexter Bradshaw, Johannes Klein, Ivan Mitic, Michael Rys, Mostafa Elhemali, Brian Swan, Mike Liddell, Xi Fang, and Chuan Liu.
Besides unit tests, we have used WASB as the default file system in our service product. (HDFS is also used but not as default file system.) Various different customer and test workloads have been run against clusters with such configurations for quite some time. The current version reflects to the version of the code tested and used in our production environment.