Erlang is a programming language and runtime system designed for building massively scalable soft real-time systems with requirements for high availability. It uses lightweight processes and message passing for concurrency and distribution. Processes have their own memory and mailboxes for communication, allowing fault tolerance through redundancy. Erlang is well-suited for building distributed, concurrent applications like chat servers and routing meshes.

1. Erlang
Built for concurrent, distributed systems
July 27, 2011
Ken Pratt
http://kenpratt.net/
Wednesday, July 27, 2011

2. The philosophy
"Erlang was designed for writing
concurrent programs that "run forever""
- Joe Armstrong
Wednesday, July 27, 2011

3. The philosophy
Simple language
Ultra-lightweight concurrency
No shared state
Local & remote communication via messaging
Wednesday, July 27, 2011

4. The language
Functional
Pattern matching
No variables! (well, they don’t vary, anyway)
Compiled to bytecode, runs on VM
Wednesday, July 27, 2011

5. The VM
Processes
Pre-emptive scheduler
Memory manager
Mesh networking
Wednesday, July 27, 2011

6. Erlang == distributed OS?
Erlang is not so much a programming language as it is
a distributed Operating System.
It’s like an ant colony with thousands of ants performing
all sorts of different tasks.
Erlang is to threads what garbage collection is to
manual memory management -- it brings concurrent
programming into the 21st century.
Wednesday, July 27, 2011

7. Local architecture
= light-weight process with a built-in mailbox
Wednesday, July 27, 2011

8. Distributed architecture
= light-weight process with a built-in mailbox
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9. Interesting architectures
Having thousands of lightweight “threads” really opens
up the architecture options.
The main example application on the “Erlang and OTP
in Action” book is a cache using one process per
cache entry!
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10. Standard library
Common patterns do all the concurrency heavy lifting
for you (gen_server, rpc)
Supervision trees
Hot code deployment
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11. In production
Chat backend SimpleDB Orchestration of
Ruby services
Routing mesh,
logging system
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12. Erlang + Neo4j
Erlang has graphs: http://www.erlang.org/doc/man/
digraph.html
BUT, it’s no Graph DB
Wednesday, July 27, 2011

13. Erlang + Neo4j
Nerlo: http://github.com/nerlo/nerlo (Jinterface-based)
Cali: http://github.com/dmitriid/cali (Jinterface-based)
Both look pretty dead-in-the-water (no commits on
either project in ~1 yr)
BUT, Jinterface works well, so does Mule ESB. So in
the worst case you could write your Neo4j adapters in
the JVM and bridge to Erlang with a biz-logic-level API.
Wednesday, July 27, 2011

14. Resources
Wednesday, July 27, 2011