A code-free presentation about the core principles and philosophies of Erlang, explaining how the whole is greater than the sum of its parts. This presentation takes a perspective rooted in showing the reasoning between each of the building blocks (message-passing, isolated processes, links and monitors, and so on), and shows how they can be assembled together to create larger systems where interactions between subsystems take a front seat in defining the fault tolerance of these systems.

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FRED HEBERT
THE ZEN OF ERLANG

2. 2
LET IT CRASH

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BLOW
IT UP
ROCKET SCIENCE

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CONTROLLED BURNS
FIGHT FIRE WITH FIRE

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PROCESSES
FULLY ISOLATED

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ASYNCHRONOUS
MESSAGE PASSING

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LINKS &
MONITORS
CODIFYING DEPENDENCIES

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PREEMPTIVE
SCHEDULING
DON’T TRUST THE DEVS

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FAILOVERS
NETWORK AWARE

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LET IT CRASH

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SUPERVISION
TREES
STRUCTURE INTERACTIONS

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Old
New
1 13 32
Old
New
1 3 1 2 3
Old
New
1 1 13 2 3
SUPERVISORS
strategies

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WHY
RESTARTING
WORKS
HEISENBUGS & FRIENDS

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REPEATABLE TRANSIENT
CORE FEATURE EASY HARD
SECONDARY
FEATURE
EASY, OFTEN
OVERLOOKED
HARD
Why restarting works
EASE OF FINDING BUGS IN DEVELOPMENT

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REPEATABLE TRANSIENT
CORE FEATURE SHOULD NEVER ALL THE TIME
SECONDARY
FEATURE
PRETTY OFTEN ALL THE TIME
Why restarting works
BUGS THAT HAPPEN IN PRODUCTION

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REPEATABLE TRANSIENT
CORE FEATURE NO YES
SECONDARY
FEATURE
DEPENDS YES
Why restarting works
BUGS HANDLED BY RESTARTS

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“I LIKE STATICALLY TYPED
LANGUAGES, AND I RESTART MY
DAEMON AFTER UNHANDLED
EXCEPTIONS. WHAT IS ERLANG
GONNA WIN ME ON FAULT
TOLERANCE?”
- FORUM USER “Notorious b.s.d.”

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ROOT
TALLY
DISTRICT
QUEBEC ONTARIO …
COUNT OCR
C_OCR
WORKER
POOL
STORAGE
CACHE
POOL
WORKER
POOL
WORKER
POOL
WORKER
WEB
SERVER
LIVE
REPORTS
SESSIONS
…
WEB
WORKER
WEB
WORKER
WEB
WORKER
SUPERVISION TREES

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ROOT
TALLY
DISTRICT
QUEBEC ONTARIO …
COUNT OCR
C_OCR
WORKER
POOL
STORAGE
CACHE
POOL
WORKER
POOL
WORKER
POOL
WORKER
WEB
SERVER
LIVE
REPORTS
SESSIONS
…
WEB
WORKER
WEB
WORKER
WEB
WORKER
SUPERVISION TREES

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ROOT
TALLY
DISTRICT
QUEBEC ONTARIO …
COUNT OCR
C_OCR
WORKER
POOL
STORAGE
CACHE
POOL
WORKER
POOL
WORKER
POOL
WORKER
WEB
SERVER
LIVE
REPORTS
SESSIONS
…
WEB
WORKER
WEB
WORKER
WEB
WORKER
SUPERVISION TREES
REPORT_APP
TALLY_APP
STORAGE_APP

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but probably not…
HOPEFULLY
SLEEP AT NIGHT

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EXPECT FAILURE

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DANGER ZONE
laid-back area
The risk of getting comfortable
WELL-DEFINED OPERATING CONDITIONS ERODE OVER TIME

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HOW THINGS
INTERACT
IN A NUTSHELL

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Totally advertising free books to you all
QUESTIONS?
@MONONCQC