Erlang. measurements and benefits.

1. Erlang.
Measurements and benefits
Valerii Vasylkov, Timecode LLC.

2. History
notes

3. Erlang shots

4. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Let it crash
Distributed Computation
Debugging and profiling
Hot upgrades

5. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Let it crash
Distributed Computation
Debugging and profiling
Hot upgrades

6. Functions are easy
Dynamic types
Pattern matching
No mutable data
structures
Binary tree search
Factorial function

7. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Let it crash
Distributed Computation
Debugging and profiling
Hot upgrades

8. Pattern matching and steroids
Structure
s
Binaries
Complex
conditions1 get_vh_registered_users(Server, [{prefix, Prefix}, {limit, Limit}, {offset, Offset}])
2 when is_list(Prefix) and is_integer(Limit) and is_integer(Offset) ->
3 case [{U,S} || {U, S} <- get_vh_registered_users(Server), lists:prefix(Prefix, U)]
of
4 [] ->
5 [];
6 Users ->
7 Set = lists:keysort(1, Users),
8 L = length(Set),
9 Start = if Offset < 1 -> 1;
10 Offset > L -> L;
11 true -> Offset
12 end,
13 lists:sublist(Set, Start, Limit)
14 end.
* Not your familiar Regex string matching

9. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Let it crash
Distributed Computation
Debugging and profiling
Hot upgrades

10. Erlang concurrency philosophy
The Actor Model
Thinking Parallel
Thinking Processes

11. • Behavior
• State
• Parallel
• Asynchronous Messages Mailboxes
• No Shared State
The Actor
Model
Carl Hewitt
1973

12. • Data + Code + Process
• Self-Contained Machines
• Stronger Encapsulation
• Less Inheritance
• Type Inference
• Hot Code Upgrades
Actor
structure
Behavior way
• Inheritance of Behavior only.
• Usually only one level deep.
• Usually one of the standard OTP behaviors:
• Generic Server
• Event
• State Machine
• Supervisor.

13. Actor vs. OO workflow
Synchronous Calls
Asynchronous Messages

15. Actor Model: Benefits
• More true to the real world
• Better suited for parallel hardware
• Better suited for distributed architectures
• Scaling garbage collection (gc/actor)
• Less Magic

16. Actors example
-module(pingpong).
-export([start/0]).
-export([ping/0, pong/0]).
start()->
PingPid = spawn(?MODULE, ping(), []),
PongPid = spawn(?MODULE, pong(), []),
PingPid ! {ping, PongPid},
erlang:send_after(60000,PingPid, stop),
erlang:send_after(60000,PongPid, stop).
ping()->
receive
{Pid, ping} ->
io:fwrite("Ping received Pong~n",[]),
timer:sleep(3000),
Pid ! {self(), pong},
ping();
stop ->
true
end.
pong() ->
receive
{Pid, pong} ->
io:fwrite("Pong received Ping~n",[]),
timer:sleep(3000),
Pid ! {self(), ping},
pong();
stop ->
true
end.

17. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Let it crash
Distributed Computation
Debugging and profiling
Hot upgrades

18. Fault-tolerant
Erlang

19. Supervisors

20. Links and Monitors

21. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Let it crash
Distributed Computation
Debugging and profiling
Hot upgrades

22. Faulty subsystem are difficult to
correct
P.S. Don’t bother, just

23. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Distributed Computation
Debugging and profiling
Hot upgrades

24. Distributio
n
Node 1 Node 2
B ! Msg
A B C
transparent message passing in cluster

25. Setting up an Erlang cluster
erl -sname ketchup
...
(ketchup@ferdmbp)1>
(ketchup@ferdmbp)1> net_kernel:connect_node(fries@ferdmbp).
true
(ketchup@ferdmbp)2> node().
ketchup@ferdmbp
(ketchup@ferdmbp)3> nodes().
[fries@ferdmbp]
(ketchup@ferdmbp)4> register(shell, self()).
true
(ketchup@ferdmbp)5> {shell, fries@ferdmbp} ! {hello, from, self()}.
{hello,from,<0.52.0>}
(ketchup@ferdmbp)6> flush().
Shell got <<"hey there!">>
ok
erl -sname fries
...
(fries@ferdmbp)1>
(fries@ferdmbp)1> register(shell, self()).
true
(fries@ferdmbp)2> receive
{hello, from, OtherShell} ->
OtherShell ! <<"hey there!">>
end.
http://learnyousomeerlang.com/distribunomico
n

26. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Distributed Computation
Debugging and profiling
Hot upgrades

27. Observer

28. Remote shells
(salad@ferdmbp)1>
User switch command
--> h
c [nn] - connect to job
i [nn] - interrupt job
k [nn] - kill job
j - list all jobs
s [shell] - start local shell
r [node [shell]] - start remote shell
q - quit erlang
? | h - this message
--> r mustard@ferdmbp
--> j
1 {shell,start,[init]}
2* {mustard@ferdmbp,shell,start,[]}
--> c
Eshell V5.8.4 (abort with ^G)
(mustard@ferdmbp)1> node().
mustard@ferdmbp

29. Debugger and profilers
Tool Results
Size of
Result
Effects on Program
Execution Time
Records
Number of
Calls
Records
Execution
Time
Records
Called by
Records
Garbage
Collection
fprof
Per process to
screen/file
Large Significant slowdown Yes
Total and
own
Yes Yes
eprof
Per process/function
to screen/file
Medium Small slowdown Yes Only total No No
cover
Per module to
screen/file
Small Moderate slowdown Yes, per line No No No
cprof Per module to caller Small Small slowdown Yes No No No
dbg Text based tracer Large Small slowdonw No No Yes No
Communit
y
• recon
• redbug
• lager
• xprof
More
introspection
• etop
• pman
• os_mon
• debugger

30. Bottleneck detection

31. Erlang benefits
Functional nature
Pattern matching on steroids
Concurrency
Fault Tolerance
Distributed Computation
Debugging and profiling
Hot upgrades

32. Hot code upgrades

33. Erlang applications pie

34. Measurements
Activity
• millions active users
• fast processes for handling
Stability
• developers and operations sleeps fine
• no emergencies for a couple of years
Performance
• compatible to C,
• VM memory management
• lightweight concurrency
• scalability from a box
Issues
• concurrent bottlenecks
• Net splits
• Networks security
• Hot upgrades

35. Top 5 lines of code
46292
11703
7328
2784
1479

36. Questions?