Lessons from Erlang - Speaker Deck

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Lessons From Erlang Michał Ślaski @michalslaski ! ! ! PolyConf, Poznań, 31.10.2014

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Erlang timeline and my background

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Erlang timeline and my background Started out in the Ericsson software lab 1987 (!)

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Erlang timeline and my background Started out in the Ericsson software lab 1987 (!) • I was six years old 

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Erlang timeline and my background Started out in the Ericsson software lab 1987 (!) • I was six years old  Released as open source in 1998

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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 

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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

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Maintenance vs. Development

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Maintenance vs. Development Maintenance may span for 20 years,  whereas development may be 1-‐2 years. ! ! ! ! ! ! ! ! ! Schach, R., Software Engineering  Fourth Edition, McGraw-‐Hill, Boston, MA 1999 

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Erlang properties

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Erlang properties OTP behaviours • set of design patterns • client-‐server, fsm, supervisor • application, release 

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Erlang properties OTP behaviours • set of design patterns • client-‐server, fsm, supervisor • application, release  What for? • consistent maintenance procedures • one tar ball artefact

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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) (abacus@127.0.0.1)1> github.com/michalslaski/erlang-‐workshop

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Erlang properties

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Erlang properties Robustness • simple and consistent error recovery • supervision hierarchies • program for the correct case • let it crash 

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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

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Erlang properties -‐ supervision tree

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Erlang properties -‐ supervision tree

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Erlang properties -‐ supervision tree

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Erlang properties -‐ supervision tree supervisor

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Erlang properties -‐ supervision tree supervisor worker

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Erlang properties -‐ supervision tree supervisor worker

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Erlang properties -‐ supervision tree supervisor worker

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Erlang properties -‐ supervision tree supervisor worker

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Erlang properties

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Erlang properties Distribution • explicit or transparent distribution • network-‐aware runtime system 

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Erlang properties Distribution • explicit or transparent distribution • network-‐aware runtime system  What for? • remote Erlang shell (REPL) • remote observing tools

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Erlang properties -‐ distribution

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Erlang properties -‐ distribution cat

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Erlang properties -‐ distribution cat ﬂea

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Erlang properties -‐ distribution cat ﬂea nodes() = [cat@home, flea@home]

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Erlang properties -‐ distribution cat dog ﬂea bird nodes() = [cat@home, flea@home]

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Erlang properties -‐ distribution cat dog ﬂea bird nodes() = [cat@home, flea@home] nodes() = [dog@home, bird@home]

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Erlang properties -‐ distribution cat dog ﬂea bird nodes() = [cat@home, flea@home] nodes() = [dog@home, bird@home]

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Erlang properties -‐ distribution cat dog ﬂea bird nodes() = [cat@home, flea@home, dog@work, bird@work]

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entop vs. top

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entop vs. top

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entop vs. top https://github.com/mazenharake/entop

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Erlang properties

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Erlang properties Hot code loading • easily change code in a running system • enables non-‐stop operation • simplifies testing 

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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

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Erlang properties

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Erlang properties Tracing in Erlang VM • Tracing is turned on/off per process • function calls, message passing, GC, scheduler 

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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

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Erlang tracing courtesy of Mats Cronqvist

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Erlang tracing calls

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Erlang tracing calls redbug -‐ github.com/massemanet/eper • tracing tool built on top of erlang:trace/3

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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]

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Flame Graphs for Erlang -‐ eflame

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Flame Graphs for Erlang -‐ eflame github.com/proger/eflame • as stacks are collected through tracing,  blocking calls are noticed and are drawn in blue

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Flame Graphs for Erlang -‐ eflame github.com/proger/eflame • as stacks are collected through tracing,  blocking calls are noticed and are drawn in blue

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What’s next?

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Erlang the Movie

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Erlang the Movie

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Erlang the Movie II

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Erlang the Movie II

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Open source projects

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Open source projects • RabbitMQ message broker  

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Open source projects • RabbitMQ message broker   • MongooseIM XMPP server 

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Open source projects • RabbitMQ message broker   • MongooseIM XMPP server  • Riak database 

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Open source projects • RabbitMQ message broker   • MongooseIM XMPP server  • Riak database  • CouchDB database

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Erlang Community

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Erlang Community Erlang Central • www.erlangcentral.org 

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Erlang Community Erlang Central • www.erlangcentral.org  Erlang Factory • Berlin, December 4 • San Francisco, March 26-‐27 

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Erlang Community Erlang Central • www.erlangcentral.org  Erlang Factory • Berlin, December 4 • San Francisco, March 26-‐27  Lambda Days • Kraków, February 26-‐27