Introduction

What is Hadoop?

Open source framework supported by Apache foundation:

• Store and process massive amount of data
• In a distributed way
• On “commodity” hardware (i.e. not expensive)
• Fault tolerant

A complex ecosystem

Numerous Apache Software Foundation projects:

• Each covering a specific functionnality
• With their own developer community
• And their own development cycle

Hadoop distributions!

• Cloudera/Horthonworks (2018 fusion)
• MapR
• Others smaller

HDFS and MapReduce principles

Two main components of Hadoop

• Distributed Software Defined Storage: HDFS (Hadoop Distributed File System)
• Distributed Data Processing: MapReduce

Principles

• Split and store data on a cluster of servers (with local storage)
• Process data localy (on the server which owns it)
• Horizontal scalability: add or remove machines, on the fly, for compute or storage
• Fault tolerant

Hadoop cluster components

• CLuster of “commodity” servers
• Shared Nothing architecture: only shared component is standard network
• Each machine is a node which own both storage and compute

Each cluster is composed of:

• Master nodes: handle metadata and knowledge of the whole infrastructure
• Worker nodes:
  • Host distributed pieces of data
  • Execute data processing algorithm parts

Hadoop story, from google to Spark

Spark first version in 2014.

Quizz

What are the two building blocks of Hadoop ecosystem (multiple choices)?

• Answer A: Oozie
• Answer B: HDFS
• Answer C: Map Reduce
• Answer D: Servers

Answer link Key: jo

Map Reduce exercise

Learning Python

HDFS Basics

HDFS blocks repartition

HDFS Daemons

HDFS Architecture

Quizz

What means HDFS?

• Answer A: Hadoop Distributed Functional Services
• Answer B: Hadoop Delayed File System
• Answer C: Hadoop Distributed File System
• Answer D: Hadoop Delayed Functional Services

Answer link Key: me

Map Reduce Basics

• Functional language concept
• Heavily used by Google for WWW indexing
• Colocate data and processing (with Hadoop and alikes)
• Automatic process ditribution on pieces of data (eager distribution)
• Optimized for fast processing of huge datasets
• Fault tolerant:
  • Data is replicated,
  • Individual tasks can be restarted anywhere

Wordcount (1. storage)

Wordcount (2. split)

Wordcount (3. map)

Wordcount (4. shuffle)

Wordcount (5. reduce)

Wordcount (6. result)

YaRN

• Yet Another Resource Negociator…
• Introduced in Hadoop v2
• Separation between
  • Resources scheduling and cluster state
  • Job execution and distribution

Quizz

What is the magical hidden step of distributed Map Reduce?

• Answer A: Map
• Answer B: Reduce
• Answer C: Shuffle
• Answer D: Split

Answer link Key: rs

Toward a new data management model

Host and process different kind of data

Typical Architecture

CNES Datalake infrastructure example

Quizz

What is the goal of a Datalake?

• Answer A: Host structured and filtered Data
• Answer B: Host any kind of Data, at any stages of processing
• Answer C: Standardizing Data structure

Answer link Key: tw

Data manipulation is complex

You won’t usually achieve what you want with a single MapReduce or Spark job.

Let’s say you want to train a ML model every time a text file is updated on a website and evaluate it next.

You’ll need to:

Processing pipelines

This is called a Pipeline or a workflow.

It mainly means chaining tasks or jobs together to automatically produce a result from an input.

Tasks are typically either:

• Triggered based on a date, periodicity (like Linux crontab for those who knows).
• Triggered by an external event: data availability.
• Triggered by the end of the previous task or tasks.

It is usually represented by Direct Acyclic Graphs (DAGs).

Example in Satellite ground segment

Some tools

Plenty others from Apache or in Python ecosystem.

Overview and Use cases

CNES typical use cases (1)

R&D, Studies, upstream research

• Launchers (combustion, structure)
• Flight dynamics, orbitography
• Sensor data simulation
• Satellite structure and materials
• Technical domain: MPI, HTC, Big Data, AI

CNES typical use cases (2)

Data production and diffusion

• Continuous data production (L0 –> L2)
• Data portals, catalogs
• Processing or reprocessing campains
• Technical Domain: HTC
• CNES Projects: SWOT, THEIA, SWH, SSALTO, PEPS

CNES typical use cases (3)

Data analysis, dowstream research

• Scientific studies on data prodcuts
• Multi temporal or cross domain analysis
• EO or astronomical Data
• Technical Domain: HTC, Big Data, AI
• CNES labs or projects : CESBIO, LEGOS, AI4Geo, EOLab

Architecture, big picture

Several things: Login nodes, Admin/Scheduler nodes, Compute resources, Parallel FS, RMDA Network

Job scheduler

• Job Queuing System
• Job = Resources, Walltime, Queue, Account, etc.
• Resources management and scheduling
• Priority, fairshare partition, QoS
• SLURM, PBS, SGE, LSF, etc.

#!/bin/bash
#SBATCH --job-name=serial_job_test    # Job name
#SBATCH --ntasks=1                    # Run on a single CPU
#SBATCH --mem=1gb                     # Job memory request
#SBATCH --time=00:05:00               # Time limit hrs:min:sec
#SBATCH --output=serial_test_%j.log   # Standard output and error log

module load python

python /data/training/SLURM/plot_template.py

High Performance Storage

• POSIX file system
• Usually based on powerfull SAN storage infrastructure
• High performance and capacity: millions IO/s, hundreds GB/s, hundreds PB capacity.
• Spectrum Scale (GPFS) and Lustre
• Other players: WekaIO, BeeGFS

Software technologies

• Classical HPC: C and Fortran
  • Compiled languages, hardware optimized
  • MPI & OpenMP
  • CUDA, OpenACC
• More and More: Python, Julia
  • Interpreted Languages, easyer to use
  • Lots of performant libraries to reuse (e.g. Numpy, Scipy, Pandas, etc.)
  • Parallel and distributed computations:
    • Multiprocessing
    • MPI4Py : Python over MPI
    • Dask, Ray, etc.

HPC platform, story and use case

HPC = High Performance Computing

• Firsts HPC platforms built in the 1960s
• Mainly compute bounds algorithms
• At first for Weather forcasting and Aerodynamic research
• Structure modeling and fluid mecanics by discretization
• Needs (needed?) high performance hardware (network, CPUs, storage)
• Compute and storage are separated
• Uses a resource scheduler

TOP500

Top 500 (june 2021)

Big Data and Hadoop

• First platforms in the 2000’s
• Mainly data bound algorithms
• Limitation in standard ethernet network performances = data locality
• At first for web indexing, or large amount of textual or tabular data analysis
• Web giant problem, then banking or IT stuf
• Use commodity hardware
• Compute and storage colocated

HPDA convergence

• Hadoop world step towards HPC: YaRN, equivalent to HPC resources scheduler
• HPC step towards Big Data: hardware not so specialized
• Hadoop big limitation: non standard File System and compute and storage colocation
• HPC big limitation: storage can be difficult to scale

Cloud computing basics

Hence the cloud computing model…

• Compute resources separated from storage (but proximity is key)
• Can host anything, at first not compute oriented
• Object store model: Software Defined Storage as HDFS, specific interface (S3)
• Horizontal scalability of compute AND storage
• Resources on demand, mutualized between millions of users
• Infinite resources like for user

Distributed programming: Hadoop vs HPC vs Cloud

Machine Learning Computations

Machine learning

• Either lots of data in inputs
• Or lots of models to train (hyperparameter search)
• And of course data preprocessing
• Big Data or HPC or Cloud

GPGPU

• Specific hardware (expensive)
• Really efficient for Deep Learning algorithms
• Image processing, Language processing

Quizz

How Big Data processing differs from classical HPC (multiple choices)?

• Answer A: It is compute bound
• Answer B: It is data bound
• Answer C: It uses specialized hardware
• Answer D: It uses commodity hardware
• Answer E: It is fault tolerant

Answer link Key: xf

Business Intelligence

Business intelligence (BI) comprises the strategies and technologies used by enterprises for the data analysis of business information.

BI technologies provide historical, current, and predictive views of business operations.

Wikipedia

Business Intelligence can use Big Data ecosystems, but is more commonly considered something different.

https://medium.com/doctolib/data-engineers-are-no-longer-data-folks-d10d44712580 https://alphalyr.fr/blog/difference-bi-business-intelligence-big-data/

Classical BI key points

• Build data systems from Business questions
• KPI and business decisions oriented
• Data warehouse, mainframe = Big server with closed technology
• Use structured data, like SQL databases,
• Oriented towards Data Value

Big Data key points

• Find insights from the data systems,
• KPI and business of course, but many more use cases
• Distributed architecture, lot of Open Source
• Different toolset (Hadoop, Python),
• Every data flavor, keep anything!
• Data Volume, Variety, Velocity

Is Hadoop dead?

Not quite yet. Still used in many places

Future of Big Data

Infrastructure: Private or public cloud, and HPC(DA) in some cases.

Quizz

What technologies are replacing Hadoop ecosystem (multiple choices)?

• Answer A: Map Reduce
• Answer B: MPI (Message Passing Interface)
• Answer C: Spark
• Answer D: Cloud computing and object storage

Answer link Key: ez