Hadoop’s org.apache.hadoop.fs.FileSystem is generic class to access and manage HDFS files/directories located in distributed environment. File’s content stored inside datanode with multiple equal large sizes of blocks (e.g. 64 MB), and namenode keep the information of those blocks and Meta information. FileSystem read and stream by accessing blocks in sequence order. FileSystem first get blocks information from NameNode then open, read and close one by one. It opens first blocks once it complete then close and open next block. HDFS replicate the block to give higher reliability and scalability and if client is one of the datanode then it tries to access block locally if fail then move to other cluster datanode. Continue reading

Hadoop MapReduce

HDFS stores file in multiple equal large size block e.g. 64 MB, 128 MB etc. and MapReduce framework access and process these files in distributed environment.
The MapReduce framework works on key-value pairs, it has two key part Mapper and Reducer.Map Reducers read file and split and pass to Mapper. Mapper set the input as key-value pairs and pass to the intermediate for sorting and shuffling. Reducer takes the key and list of value, process and writes to the disk. Continue reading

Grails – GSP


Grails uses GSP for the presentation tier. The Groovy in Groovy Server Pages not only identifies the underlying technology, but also the language you can use if you want to write a quick scriptlet or two. Groovy Taglib and partial templates give you a more sophisticated way of sharing code and behavior across Web pages. Continue reading

Grails Scaffolding Controllers and Views


Controllers and views round out the “Big Three” in Grails applications. The Model/View/Controller (MVC) pattern is undoubtedly familiar to most web developers. By enforcing a clean separation of concerns among these three elements, your efforts are paid back in terms of maximum flexibility and reuse. Continue reading