The document discusses the pros and cons of Erlang, highlighting its unsuitability for certain tasks, a steep learning curve, and syntax challenges, along with improvements like the introduction of Elixir and the Dialyzer for type analysis. It emphasizes the benefits of Erlang, including less code, fewer engineers required, high availability, scalability, and a supportive community. The author, an experienced Erlang developer, presents a balanced view indicating both challenges and advancements in the Erlang ecosystem.

1. Erlang Developments
Enrique Paz @quiquepaz
1/22

2. Introduction About me
Erlang Developer since 2008
Developing voteraise.com in Ocaml
Trying tech leadership @KPN
2/22

3. Introduction Disclaimer
sort_for_talk([Good,Bad,Ugly])-
[Bad,Ugly,Good].
All comments to come are personal opinions.
Read others’ in the WWW before making up your own
3/22

4. The Bad
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5. The Bad (Un)Suitability
Erlang is not a silver bullet
Number Crunching
Text/String Processing
XML and SOAP based Web Services
“All can be done given time and money” - Ferenc Holzhauser
5/22

6. The Bad Learning Curve
Design: Processes VS Objects
I Technical knowledge required
I Domain knowledge is harder to map
Functional Programming
I Awesome (if you’ve felt the imperative pain)
I Risk of callback hell
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7. The Bad What has improved
Learn You Some Erlang
Erlang Solutions Webinars
Erlang OTP in Action
Designing for Scalability with
Erlang OTP
7/22

8. The Ugly
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9. The Ugly Syntax
Erlang
myfun(Opts) -
What = proplists:get_value(what,Opts,some),
io:format(Doing ~s~n, [What]),
L = [1, 2, 3],
lists:foldl(fun(X, Acc) -
X + Acc
end, 0, L).
9/22

10. The Ugly Syntax
Erlang
myfun(Opts) -
What = proplists:get_value(what,Opts,some),
io:format(Doing ~s~n, [What]),
L = [1, 2, 3],
lists:foldl(fun(X, Acc) -
X + Acc
end, 0, L).
Python
myfun(what=some):
print (Doing {thing}.format(thing=what)
l = [1, 2, 3,],
return reduce(lambda x, y: x + y, l, 0)
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11. The Ugly (lack of) Typesystem
Erlang
myfold(F, Acc, []) - Acc;
myfold(F, Acc, [H|T]) - myfold(F, F(H,Acc), T).
myfold(fun(X) - X + 1 end, 0, [1, 2, 3]).
% Error on runtime!!
10/22

12. The Ugly (lack of) Typesystem
Erlang
myfold(F, Acc, []) - Acc;
myfold(F, Acc, [H|T]) - myfold(F, F(H,Acc), T).
myfold(fun(X) - X + 1 end, 0, [1, 2, 3]).
% Error on runtime!!
Ocaml
let rec myfold f acc = function
| [] - Acc
| h::t - myfold f (f h acc) t
# val myfold:(’a -’b-’b)-’b-’a list-’b=fun
myfold (fun x - x+1) 0 [1;2;3]
# Compilation error!! (could have used (+))
10/22

13. The Ugly What has improved
Elixir: a new language for the Erlang VM
def myfun(what ’some’) do
IO.puts Doing #{what}
l = [1, 2, 3]
List.foldl l, 0, (1 + 2)
end
11/22

14. The Ugly What has improved
Elixir: a new language for the Erlang VM
def myfun(what ’some’) do
IO.puts Doing #{what}
l = [1, 2, 3]
List.foldl l, 0, (1 + 2)
end
I Direct mixing of Erlang and Elixir code
I Ruby-like syntax
I Adoption?
11/22

15. The Ugly What has improved
Dialyzer: Static type analyzer for Erlang code
-type opt()::{what, string()}.
-spec my_fun([opt()]) - pos_integer().
12/22

16. The Ugly What has improved
Dialyzer: Static type analyzer for Erlang code
-type opt()::{what, string()}.
-spec my_fun([opt()]) - pos_integer().
I Improved error catching
I Improved error reporting
I Ideally, all the code you use should be typed
I Still no support for ETS and debugger match_specs
I Dialyxir for Elixir projects
12/22

17. The Good
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18. The Good Less Code
Functional = re-usability
OTP framework: structure and patterns
In code assertions / Let it crash
ok = file:write_file(MyFile, Hello!)
Bit syntax
?IP_VERSION:4, HLen:4, SrvcType:8,
TotLen:16, ID:16, Flgs:3, FragOff:13,
TTL:8, Proto:8, HdrChkSum:16, SrcIP:32,
DestIP:32, RestDgram/binary = IpPkg
14/22

19. The Good Less Engineers
High engineering level
I Not trivial to learn
I Usually not the 1st language
The WhatsApp example:
I 450M users
I 25 Engineers building client Apps
I 6 Erlang Engineers building the server
I 75M users / Erlang Engineer
15/22

20. The Good Highly Available
Availability1 of Erlang based telephone switches in late
1980s
AXD301 reported 9.99999999%
(nine nines) availability
0.6 seconds per 20 years
1Joe Armstrong: http://pragprog.com/articles/erlang
16/22

21. The Good Highly Available
Supervision trees provide automatic recovery
No downtime system upgrades
1. Create appup
2. Generate relup
3. Deploy relup
4. Instruct target system to upgrade itself
17/22

22. The Good Scalable
Light Parallel processes
I Quick to create: 660K processes/sec
I 300 words / standard process (2.4KB)
I No shared memory 2
I 1 process per: user session, HTTP call. . .
Well known bottlenecks
I gen_server serialization
I Long lived NIFs
I Disk I/O
2almost
18/22

23. The Good The community
Erlang Mailing List
Erlang Central LIVE chat
Erlang Camp
Erlang Factory (San Francisco)
Erlang User Conference (Stockholm)
Erlang Factory Lite: Berlin, Moscow,
NY, Paris, Chicago. . .
19/22

24. The Good What has improved
Forced wake up (+sfwi) for schedulers
ETS concurrency
enif_schedule_nif/0 for partitioned NIF invocation
Scalability on multicore (RELEASE)
And a ton of awesome applications:
I Nifty
I Cowboy
I Concuerror
I Piqi
I . . . and, of course. . .
20/22

25. The Good What has improved
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26. Wrapping up Questions
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