Apache Hadoop MapReduce

What is it ? Why use it ? How does it work Some examples Big users

MapReduce – What is it ?

Processing engine of Hadoop Developers create Map and Reduce jobs Used for big data batch processing Parallel processing of huge data volumes Fault tolerant Scalable

MapReduce – Why use it ?

Your data in Terabyte / Petabyte range You have huge I/O Hadoop framework takes care of

Job and task managementFailuresStorageReplication You just write Map and Reduce jobs

MapReduce – How does it work ?

Take word counting as an example, something that Google does all of the time.

MapReduce – How does it work ?

Input data split into shards Split data mapped to key,value pairs i.e. Bear,1 Mapped data shuffled/sorted by key i.e. Bear Sorted data reduced i.e. Bear, 2 Final data stored on HDFS There might be extra map layer before shuffle JobTracker controls all tasks in job TaskTracker controls map and reduce

MapReduce - Some examples

A visual example with colours to show you the cycleSplit -> Map -> Shuffle -> Reduce

MapReduce - Some examples

A visual example of MapReduce with job and task trackers added to individual map and reduce jobs.

Hadoop MapReduce – Big users

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