Erlang????

1
Erlang????

• ?? 2009/03/11
• http//blog.yufeng.info

2
What is Erlang

• Erlang is a general-purpose programming language
  and runtime environment. Erlang has built-in
  support for concurrency, distribution and fault
  tolerance. Erlang is used in several large
  telecommunication systems from Ericsson.

3
What sort of applications is Erlang particularly
suitable for

• Distributed, reliable, soft real concurrent
  systems.
• Telecommunication systems, e.g. controlling a
  switch or converting protocols.
• Servers for Internet applications, e.g. a mail
  transfer agent, an IMAP-4 server, an HTTP server
  or a wap stack
• Telecommunication applications, e.g. handling
  mobility in a mobile network or providing unified
  messaging.
• Database applications which require soft realtime
  behaviour.
• Erlang is good at solving these sorts of problems
  because this is the problem domain it was
  originally designed for. Stating the above in
  terms of features
• Erlang provides a simple and powerful model for
  error containment and fault tolerance (supervised
  processes).

4
???

• Concurrency and message passing are a fundamental
  to the language. Applications written in Erlang
  are often composed of hundreds or thousands of
  lightweight processes. Context switching between
  Erlang processes is typically one or two orders
  of magnitude cheaper than switching between
  threads in a C program.
• Writing applications which are made of parts
  which execute on different machines (i.e.
  distributed applications) is easy. Erlang's
  distribution mechanisms are transparent programs
  need not be aware that they are distributed.
• The OTP libraries provide support for many common
  problems in networking and telecommunications
  systems.
• The Erlang runtime environment (a virtual
  machine, much like the Java virtual machine)
  means that code compiled on one architecture runs
  anywhere. The runtime system also allows code in
  a running system to be updated without
  interrupting the program.

5
What is OTP?

• OTP (Open Telecom Platform) is a large collection
  of libraries for Erlang to do everything from
  compiling ASN.1 to providing a WWW server. Most
  projects using "Erlang" are actually using
  "Erlang/OTP", i.e. the language and the
  libraries. OTP is also open source.

6
Erlang???

• ???
• ???SMP???
• ???????
• ???????
• ??????????????
• ???????

7
???????????Erlang???

• ??Reia????
• ???????
• ??
• ??
• ???
• ??
• ??

8
Erlang????

• ????
• ????
• ??????
• ????
• ?????????
• ?????
• ??????
• ????

9
Erlang?????

• 200K?C?? ???Erlang??
• ???ACE??
• ?????
• ???? ??????
• 1.5M
• ???????? ?p2p

10
Erlang ERTS????????????

• IO??
• kernel poll ?epoll kqueue
• ?????
• timewheel
• ??????
• process
• coroutine
• fiber
• smp

11
????????

• ???????
• ???????
• ?????
• ????

12
????????

• ??
• ???
• ????
• driver?????
• ????
• process_lock
• ???mutex
• ??
• PORT ????

13
???PORT

• ??Unix??? ??????
• ??????CGI
• ?????????
• ??????????

14
???????

• C??(EI)
• Java (jinterface)
• Cobra
• TCP/HTTP

15
RPC

• ???RPC
• ???????up down
• ???????????
• ??????

16
?????

• ?????
• ???? ?????????
• ????????
• ??? ?????

17
????

• OS mon
• SNMP
• HTTP

18
????

• ?????????? Diskless
• ????? ????????
• ????

19
????

• ?????shell
• ssh sftp
• ????

20
????

• Windows
• (smp?????)
• nix
• ??????????

21
?????????

• Erlang ??? ACE
• ????? ??
• ????
• ????
• ????
• ????

22
????

• FP??
• ?????
• ???
• ???

23
????

• Facebook
• ??
• ??
• ??
• ???startup??

24
QA

• ????