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Lessons From Erlang
Michał Ślaski @michalslaski !
!
!
4Developers, 20.04.2015
Erlang timeline and my background
Erlang timeline and my background
Started out in the Ericsson software lab 1987 (!)
Erlang timeline and my background
Started out in the Ericsson software lab 1987 (!)• I was six years old
Erlang timeline and my background
Started out in the Ericsson software lab 1987 (!)• I was six years old
Released as open source in 1998
Erlang timeline and my background
Started out in the Ericsson software lab 1987 (!)• I was six years old
Released as open source in 1998• I started computer science at AGH 2 years later
Erlang timeline and my background
Started out in the Ericsson software lab 1987 (!)• I was six years old
Released as open source in 1998• I started computer science at AGH 2 years later
Gains SMP support in 2005
Erlang timeline and my background
Started out in the Ericsson software lab 1987 (!)• I was six years old
Released as open source in 1998• I started computer science at AGH 2 years later
Gains SMP support in 2005• I just graduated and joined Erlang Solutions
Maintenance vs. Development
Maintenance vs. Development
Maintenance may span for 20 years,whereas development may be 1-‐2 years.
!!!!!!
!!
!Schach, R., Software EngineeringFourth Edition, McGraw-‐Hill, Boston, MA 1999
Erlang properties
Erlang properties
OTP behaviours • set of design patterns • client-‐server, fsm, supervisor • application, release
Erlang properties
OTP behaviours • set of design patterns • client-‐server, fsm, supervisor • application, release
What for? • consistent maintenance procedures • one tar ball artefact
Erlang OTP releases
$ ls -l ../abacus.tar -rw-r--r-- 1 ms staff 12331520 Oct 31 12:01 abacus.tar !$ ls -1 bin erts-6.1 lib releases !$ ./bin/abacus Erlang/OTP 17 [erts-6.1] [smp:4:4] [async-threads:10] [kernel-poll:false] !Eshell V6.1 (abort with ^G) ([email protected])1>
github.com/michalslaski/erlang-‐workshop
Erlang properties
Erlang properties
Robustness • simple and consistent error recovery • supervision hierarchies • program for the correct case • let it crash
Erlang properties
Robustness • simple and consistent error recovery • supervision hierarchies • program for the correct case • let it crash
What for? • resilient to bugs and failures
Erlang properties -‐ supervision tree
Erlang properties -‐ supervision tree
Erlang properties -‐ supervision tree
Erlang properties -‐ supervision tree
supervisor
Erlang properties -‐ supervision tree
supervisor
worker
Erlang properties -‐ supervision tree
supervisor
worker
Erlang properties -‐ supervision tree
supervisor
worker
Erlang properties -‐ supervision tree
supervisor
worker
Erlang properties
Erlang properties
Distribution • explicit or transparent distribution • network-‐aware runtime system
Erlang properties
Distribution • explicit or transparent distribution • network-‐aware runtime system
What for? • remote Erlang shell (REPL) • remote observing tools
Erlang properties -‐ distribution
Erlang properties -‐ distribution
cat
Erlang properties -‐ distribution
cat
flea
Erlang properties -‐ distribution
cat
fleanodes() =
[cat@home, flea@home]
Erlang properties -‐ distribution
cat dog
flea birdnodes() =
[cat@home, flea@home]
Erlang properties -‐ distribution
cat dog
flea birdnodes() =
[cat@home, flea@home]nodes() =
[dog@home, bird@home]
Erlang properties -‐ distribution
cat dog
flea birdnodes() =
[cat@home, flea@home]nodes() =
[dog@home, bird@home]
Erlang properties -‐ distribution
cat dog
flea birdnodes() =
[cat@home, flea@home, dog@work, bird@work]
entop vs. top
entop vs. top
entop vs. top
https://github.com/mazenharake/entop
Erlang properties
Erlang properties
Hot code loading • easily change code in a running system • enables non-‐stop operation • simplifies testing
Erlang properties
Hot code loading • easily change code in a running system • enables non-‐stop operation • simplifies testing
What for? • shorter development cycle • non-‐stop operations
Erlang properties
Erlang properties
Tracing in Erlang VM • Tracing is turned on/off per process • function calls, message passing, GC, scheduler
Erlang properties
Tracing in Erlang VM • Tracing is turned on/off per process • function calls, message passing, GC, scheduler
What for? • live debugging • no need to instrument code and recompile
Erlang tracing
courtesy of Mats Cronqvist
Erlang tracing calls
Erlang tracing calls
redbug -‐ github.com/massemanet/eper • tracing tool built on top of erlang:trace/3
Erlang tracing calls
redbug -‐ github.com/massemanet/eper • tracing tool built on top of erlang:trace/3
1> redbug:start("lists:seq(X,Y) -> return"). !{30,1}!2> lists:seq(1,5).![1,2,3,4,5]! !% 12:32:17 <0.32.0>({erlang,apply,2})!% lists:seq(1, 5)! !% 12:32:17 <0.32.0>({erlang,apply,2})!% lists:seq/2 -> [1,2,3,4,5]
Flame Graphs for Erlang -‐ eflame
Flame Graphs for Erlang -‐ eflame
github.com/proger/eflame • as stacks are collected through tracing,blocking calls are noticed and are drawn in blue
Flame Graphs for Erlang -‐ eflame
github.com/proger/eflame • as stacks are collected through tracing,blocking calls are noticed and are drawn in blue
What’s next?
Erlang the Movie
Erlang the Movie
Erlang the Movie II
Erlang the Movie II
Open source projects
Open source projects
• RabbitMQ message broker
Open source projects
• RabbitMQ message broker
• MongooseIM XMPP server
Open source projects
• RabbitMQ message broker
• MongooseIM XMPP server
• Riak database
Open source projects
• RabbitMQ message broker
• MongooseIM XMPP server
• Riak database
• CouchDB database
Erlang Community
Erlang Community
Erlang Central • www.erlangcentral.org
Erlang Community
Erlang Central • www.erlangcentral.org
Erlang User Conference • Stockholm, June 2015
Erlang Community
Erlang Central • www.erlangcentral.org
Erlang User Conference • Stockholm, June 2015
Erlang Community
Erlang Central • www.erlangcentral.org
Erlang User Conference • Stockholm, June 2015
Lambda Academy • lambdaacademy.org, March-‐June 2015
Questions?
!
Michał Ślaski @michalslaski
