1.
Distributed Processing
Frameworks
Author: Antonios Katsarakis

2.
Literature
• MapReduce: Simplified Data Processing on Large Clusters
Jeff Dean et al. - OSDI’04.
• Spark: Cluster Computing with Working Sets
M. Zaharia et al. - HotCloud’10.

3.
Why Big Data?
• More data to process: IoT, smart devices, web applications
- About 2.3 trillion GB of new data are generated every day
• Growth of CPU performance cannot keep up with increasing
amount of data to process
• This leads us to the Big Data era
- Big data: Data sets are so large that the processing power of a
single machine is inadequate to deal with them
• We need to find ways to process these massive amounts of data

4.
MapReduce
• Proposed by Jeff Dean et al. (Google) 2004
- Cited more than 18k
• A programming model that enables the parallel
and distributed processing of large data sets
• Typical MapReduce Program:
- Read Data
- Map: filtering of the data
- Shuffle and short
- Reduce: summary operation on data
- Write the Results
ReduceReduce
Input Data
1/3
Input
1/3
Input
1/3
Input
Map Map Map
Interm.
Data
Interm.
Data
Interm.
Data
Output
Data
Output
Data

5.
Critical Reflection
• Outcome:
- Novel idea that lead to a whole new era of distributed systems
- Big impact in industry (Hadoop MapReduce)
- Lowered the cost of computations
• Limitations:
- Restricted to batch processing
- It only support map and reduce operations
- The shuffling phase introduces overheads

6.
Spark
• Proposed by Matei Zaharia et al. 2010
- Cited 1.5k
• Another programming model based on
higher-ordered functions that execute
user-defined functions in parallel
• Aims to replace MapReduce in industry
• Main Ideas:
- Represent the computations as DAGs
- Cache datasets into memory

7.
Spark Model
• Resilient Distributed
Datasets (RRDs):
immutable collections of
objects spread across a
cluster
• Operations over RDDs:
1.Transformations: lazy
operators that create new
RDDs
2.Actions: launch a
computation on an RDD
Pipelined
RDD1
var count = readFile(…)
.map(…)
.filter(..)
.reduceByKey()
.count()
File splited
into chunks
(RDD0)
RDD2
RDD3
RDD4
Result
Job (RDD) Graph
Stage1St.2

8.
Critical Reflection
• Benefits:
- High level API
- Support more applications types
- Performance optimizations
• Limitations:
- Detailed performance analysis on the thread level is hard
- Multipurpose application support makes performance improvements and
tuning really challenging
- The shuffling phase introduces overheads

9.
Conclusion
• Clusters provide the computational power to
process Big Data
• MapReduce allows developers to build programs for
clusters
• Spark tries to overcome limitations of MapReduce
• These systems introduce many challenges in terms
of measuring and improving their performance