The document provides an overview of the Erlang programming language and its history and uses. It describes how Erlang was originally written in Prolog, discusses its core features like concurrency, distribution and fault tolerance, and gives examples of code modules. It also summarizes Erlang's use in large telecom systems and major companies like Facebook.

1. Prolog
to
Erlang
First
version
of
Erlang
was
wri2en
in
Prolog

2. Examples

3. hello_mod.erl
1. -­‐module(hello_mod).
2. -­‐export([say_hello/0]).
3. say_hello()
-­‐>
4.
io:format("Hello~n",
[]).

4. hello_mod:say_hello().
1. $
erl
2. Erlang
R14B04
(erts-­‐5.8.5)
[source]
[64-­‐bit]
[smp:4:4]
[rq:4]
[async-­‐threads:0]
[hipe]
[kernel-­‐poll:false]
3. Eshell
V5.8.5
(abort
with
^G)
4. 1>
c(hello_mod).
5. {ok,hello_mod}
6. 2>
hello_mod:say_hello().
7. Hello
8. ok
9. 3>

5. fact_mod.erl
1. -­‐module(fact_mod).
2. -­‐export([fact/1]).
3. fact(0)
-­‐>
1;
4. fact(N)
-­‐>
N
*
fact(N
-­‐
1).

6. fact_mod:fact(4).
1. $
erl
2. Erlang
R14B04
(erts-­‐5.8.5)
[source]
[64-­‐bit]
[smp:4:4]
[rq:4]
[async-­‐threads:0]
[hipe]
[kernel-­‐poll:false]
3. Eshell
V5.8.5
(abort
with
^G)
4. 1>
c(fact_mod).
5. {ok,fact_mod}
6. 2>
fact_mod:fact(4).
7. 24
8. 3>

7. qsort_mod.erl
1. -­‐module(qsort_mod).
2. -­‐export([qsort/1]).
3. qsort([])
-­‐>
4.
[];
5. qsort([H
|
T])
-­‐>
6.
qsort([
X
||
X
<-­‐
T,
X
<
H
])
++
7.
[H]
++
8.
qsort([
X
||
X
<-­‐
T,
X
>=
H
]).

8. qsort_mod:qsort([3,
2,
1,
6,
4,
5]).
1. $
erl
2. Erlang
R14B04
(erts-­‐5.8.5)
[source]
[64-­‐bit]
[smp:4:4]
[rq:4]
[async-­‐threads:0]
[hipe]
[kernel-­‐poll:false]
3. Eshell
V5.8.5
(abort
with
^G)
4. 1>
c(qsort_mod).
5. {ok,qsort_mod}
6. 2>
qsort:qsort([3,
2,
1,
6,
4,
5]).
7. [1,2,3,4,5,6]
8. 3>

9. History
§ 1986
-­‐
Joe
Armstong
(Ericsson)
§ Prolog
§ 1988
-­‐
Ericsson
AXD301
ATM
telco
switch
§ 1
million
lines
of
Erlang
§ 99.9999999
§ 1995
-­‐
Open
Telecom
Plalorm
§ 1998
-­‐
Open
source
§ 2011
-­‐
Release
14B03

10. What s
Erlang?

11. Programming
Language
§ General-­‐purpose
§ Funcponal
§ Like
LISP,
Haskell
§ Garbage-­‐collected
§ Dynamic
typing
§ Single
assignment
§ Erlang
runpme
system
§ STDLIB

12. Features
§ Massive
concurrency
and
message
passing
§ Actor
model
§ Sos-­‐real-­‐pme
§ Thousands
of
processes
under
single
VM
§ Short
GC
pauses
§ Distributed
§ Erlang
nodes
§ Fault-­‐tolerant
§ 99.9999999%
§ Powerful
error
handling
§ Supervisors
§ Recovery
from
errors
§ Non-­‐stop
systems
§ Hot
code
swapping
in
producpon

13. Data
types
§ Atoms
§ open,
close,
`empty
§ Integers
§ Floats
§ Tuples
§ {price,
12.34}
§ Lists
§ [1,
2,
3,
4]
§ PIDs

14. Control
Structures
§ Pa2ern
matching
§ Guards
§ Higher
order
funcpons
§ List
comprehension

15. Actors:Message
Passing
§ Send
message
(client
process)
§ ServerProcessId
!
Message.
§ Receiving
a
message
(server
process)
§ receive
pa2ern2
-­‐>
…;
pa2ern2
-­‐>
…
end.

16. Erlang
VM
§ Thousands
of
processes
under
single
VM
§ Lightweight
processes
§ Garbage
collecpon
per
process
§ BEAM
files
§ Napve
code
compiler

17. Anywhere
§ OS
/
Hardware
independent
§ UNIX/Linux
§ Windows
§ Mac
§ Embedded
§ Android

18. Open
Telecom
Plalorm
OTP

19. OTP
Design
Principles
§ Supervision
trees
§ Supervisors
§ Workers
§ Behaviours
§ gen_server
§ The
server
in
client-­‐server
§ fsm_server
§ Finite
state
machines
§ gen_event
§ Event
handling
§ Applicapons
§ Applicapon
§ Releases

20. Web
Development

21. Web
Development
§ Web
Servers
§ Inets
§ Build-­‐in
§ Yaws
§ 80,000
concurrent
connecpons
(2002)
§ MochiWeb
§ Lightweight
HTTP
§ Web
Frameworks
§ ErlyWeb
§ MVC
for
Yaws
§ Erlang
Web
§ MVC
for
Yaws
and
Inets
§ Nitrogen
§ An
event-­‐driven
2.0
framework
(cometd)

22. Wri2en
in
Erlang
§ Apache
CouchDB
§ Document-­‐oriented
database
(replicapon)
§ RabbitMQ
§ Message-­‐oriented
middleware
§ Riak
§ NoSQL
database
(ring)
§ Ejabberd
§ XMPP
applicapon
server

23. Development
Tools
§ IDEs
§ Eclipse
§ Emacs
+
Distel
§ Vim
§ Tools
§ MOEBIUS
§ CI
Server
§ rebar
§ Build
and
packaging
tool

24. Erlang
in
Producpon
§ Ericsson
AXD301
telco
switch
§ 160
GB/s
§ 1
million
lines
of
Erlang
§ Hundreds
of
programmers
§ 99.9
999
999%
reliability
§ GPRS
§ GSM
cell
telco
network
§ Facebook
Chat
§ 800+
million
messages
/
day
§ GitHub
§ Goldman
Sachs
???
§ High-­‐frequency
trading
§ Deutsche
Bank