![Erlang Nuts and Bolts Hello World -module(hello). -export(hello_world/0). hello_world() -> io:format(“Hello world.~n”, []). Erlang (BEAM) emulator version 5.5.5 [source] [async-threads:0] [kernel-poll:false] Eshell V5.5.5 (abort with ^G) 1> c(hello). {ok,hello} 2> hello:hello_world(). Hello world. ok 3>](https://image.slidesharecdn.com/disrupt-1209728695730472-8/85/Disrupt-22-320.jpg)
![Spawning Processes Pid = spawn(module, function, args). For example: Erlang (BEAM) emulator version 5.5.5 [source] [async-threads:0] [kernel-poll:false] Eshell V5.5.5 (abort with ^G) 1> spawn(hello, hello_world, []). <0.32.0>Hello world. 2>](https://image.slidesharecdn.com/disrupt-1209728695730472-8/85/Disrupt-23-320.jpg)
![Message send and receive Send: Pid ! message. Receive: receive Pattern1 [when Guard1] -> Expression1; Pattern2 [when Guard2] -> Expression2; … end](https://image.slidesharecdn.com/disrupt-1209728695730472-8/85/Disrupt-24-320.jpg)
![Send/Receive Example -module(food). -export([dinner/0]). dinner() -> receive sunday -> io:format("Sunday is fish.~n", []), dinner(); monday -> io:format("Monday is chicken.~n", []), dinner(); tuesday -> io:format("Tuesday is beef.~n", []), dinner(); Other -> io:format("Time to go home.~n", []) end.](https://image.slidesharecdn.com/disrupt-1209728695730472-8/85/Disrupt-25-320.jpg)
![Send/Receive Execution Eshell V5.5.5 (abort with ^G) 1> Pid = spawn(food, dinner, []). <0.32.0> 2> Pid ! tuesday. tuesdayTuesday is beef. 3> Pid ! sunday. sundaySunday is fish. 4> Pid ! wednesday. wednesdayTime to go home. 5> Pid ! monday. monday 6>](https://image.slidesharecdn.com/disrupt-1209728695730472-8/85/Disrupt-26-320.jpg)
![And the code looks like BDB DB = ?BDB:db_create(Port, []). ?BDB:db_open(Port, DB, void, “database”, “”, bdb_DB_BTREE, [bdb_DB_CREATE, 8#644). ?BDB:db_put(Port, DB, void “foo”, “foodata”, []). {Key, Data} = ?BDB:db_get(Port, DB, void, “foo”, <<>>, []). ?BDB:db_close(Port, DB, []).](https://image.slidesharecdn.com/disrupt-1209728695730472-8/85/Disrupt-29-320.jpg)
Disrupt
- 3. Erlang + EDTK + BDB: Disrupting the Web Margo Seltzer Architect
- 4. What kind of talk is this? Evangelism FUD Fun
- 5. Erlang + EDTK + BDB: Huh? General purpose programming language Runtime system Developed by Ericsson Open source Key feature: designed for ease of developing highly-reliable, highly-concurrent systems Enables highly robust applications: The AXD 301 includes 2 million lines of Erlang Reliability: NINE 9’s
- 6. Erlang + EDTK + BDB: Huh? Erlang Driver Toolkit Declarative APIs to external library Automatic wrapper generation Tracks library resources and cleans up Enhanced for BDB support: Supports Erlang’s “crash early” error-handling model (supervisors) Meshes Erlang-style concurrency with BDB concurrency (private thread pools) Adds significant convenience layers for configration and replication Minimal overhead
- 7. Erlang + EDTK + BDB : Huh? Berkeley Database Database functionality … Transactions Recovery Replication … in a different package Library linked directly into an application Programmatic APIs Schemaless: key/data pairs
- 8. Disruptive Technology “ a technological innovation, product, or service that eventually overturns the existing dominant technology or status quo product in the market.” -- Wikipedia
- 9. Outline Interpreting the Title Disecting an Internet Service Erlang, it’s philosophy and runtime Putting it all together Q&A
- 10. An Internet Service Clients Load Balancer .NET Java The Internet App Servers Database Servers
- 11. An Internet Service Clients Load Balancer .NET Java CGI PHP LISP Perl The Internet Database Servers
- 12. An Internet Service Clients Load Balancer BDB CGI Perl Application Code The Internet Servers
- 13. The Software Architecture In any case, your software is a mess Gazillion Active Ports Fraction of a gazillion threads A relatively small number of disks
- 14. Outline Interpreting the Title Disecting an Internet Service Erlang, it’s philosophy and runtime Putting it all together Q&A
- 15. The Erlang Approach Don’t fight the problem Don’t fight the medium (the network) Don’t fight the medium (distributed software)
- 16. Don’t Fight the Problem 1:1 concurrency with the problem/solution domain Explicit lightweight stateful conversations (addressable processes) Arbitrarily rich messages
- 17. Don’t Fight the the Network Asynchronous send (location-agnostic send and pray) Ordered inbox per process Blocking receive with timeout (message-selection via pattern-matching)
- 18. Don’t Fight Distributed Software No shared memory: no mutexes, no mutation True loose-coupling: processes are free to migrate Safe to kill any process any time Recovery-oriented computing (before it was fashionable) Let it crash Propagate exceptions Know how to recover
- 19. Erlang Tricks: Processes Belong to the language (runtime), not OS Very lightweight Immutable data Asynchronous message passing Upgrade application on live, running system Implication: No big deal if a process dies
- 20. Erlang Tricks: Links Links connect processes On process crash, all linked processes get message. Notified processes can clean up, takeover, do whatever is necessary. Easy to create supervisors No recovery: just crash, cleanup and restart
- 21. Erlang Tricks: Concurrency Use concurrency to structure the application “ My first message is that concurrency is best regarded as a program structuring principle” Tony Hoare, 2001 Concurrency-oriented programming Share nothing Pure message passing Let it crash
- 22. Erlang Nuts and Bolts Hello World -module(hello). -export(hello_world/0). hello_world() -> io:format(“Hello world.~n”, []). Erlang (BEAM) emulator version 5.5.5 [source] [async-threads:0] [kernel-poll:false] Eshell V5.5.5 (abort with ^G) 1> c(hello). {ok,hello} 2> hello:hello_world(). Hello world. ok 3>
- 23. Spawning Processes Pid = spawn(module, function, args). For example: Erlang (BEAM) emulator version 5.5.5 [source] [async-threads:0] [kernel-poll:false] Eshell V5.5.5 (abort with ^G) 1> spawn(hello, hello_world, []). <0.32.0>Hello world. 2>
- 24. Message send and receive Send: Pid ! message. Receive: receive Pattern1 [when Guard1] -> Expression1; Pattern2 [when Guard2] -> Expression2; … end
- 25. Send/Receive Example -module(food). -export([dinner/0]). dinner() -> receive sunday -> io:format("Sunday is fish.~n", []), dinner(); monday -> io:format("Monday is chicken.~n", []), dinner(); tuesday -> io:format("Tuesday is beef.~n", []), dinner(); Other -> io:format("Time to go home.~n", []) end.
- 26. Send/Receive Execution Eshell V5.5.5 (abort with ^G) 1> Pid = spawn(food, dinner, []). <0.32.0> 2> Pid ! tuesday. tuesdayTuesday is beef. 3> Pid ! sunday. sundaySunday is fish. 4> Pid ! wednesday. wednesdayTime to go home. 5> Pid ! monday. monday 6>
- 27. BDB in Erlang Erlang: Is Functional (not procedural) Communicates via messages Communicates asynchronously BDB: Is Procedural Communicates via shared memory Blocks on locks/IO/etc
- 28. EDTK fixes mismatch Erlang interfaces to outside world via ports. EDTK automatically generates code that wraps library API, making library look like Erlang process(es). Provides framework to: Clean up BDB resources after a crash Manage threadpools to deal with BDB blocking Manage administrative processes Manage replication groups
- 29. And the code looks like BDB DB = ?BDB:db_create(Port, []). ?BDB:db_open(Port, DB, void, “database”, “”, bdb_DB_BTREE, [bdb_DB_CREATE, 8#644). ?BDB:db_put(Port, DB, void “foo”, “foodata”, []). {Key, Data} = ?BDB:db_get(Port, DB, void, “foo”, <<>>, []). ?BDB:db_close(Port, DB, []).
- 30. Outline Interpreting the Title Disecting an Internet Service Erlang, it’s philosophy and runtime Putting it all together Q&A
- 31. An Internet Service Clients Load Balancer Servers The Internet
- 32. How does it Perform? From: http://www.sics.se/~joe/apachevsyaws.html
- 33. Acknowledgements Joe Armstrong (Erlang) Scott Lystig Fritchie (EDTK) Chris Newcombe (EDTK extensions for BDB)
- 34. A Q &