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Behaviours
and
Applica2ons

gen_server,
supervisor
and
applica2on

What
You
Will
��ܾ��

The
Protocol

Module:Func+on(Arg1,
...,
ArgN).

<func+on
return
as
text>

In
Broad
Strokes

Step
1:
tr_server Step
2:
OTP
packaged

4

How
the
Fundamental
Pieces
Fit

Modules Send
Processes Messages
Contain Run

Func+ons Are
sent
to

Behaviour
Basics

• Behaviour
Interface
• Behaviour
Implementa2on
• Behaviour
Container

6

Take
a
Look

ex1.erl
-‐>
ex2.erl
-‐>
ex2behaviour.erl

Example
Behaviour
• Behaviour
Interface
– init/0
– handle_msg/2
• Behaviour
Implementa3on
– ex2
module
• Behaviour
Container
– ex2behaviour
module
– 1
to
1
process
model
– contained
in
the
ex2behaviour
module

8

gen_server
Interface
init/1

ronous
handle_call/3

asyncronous
handle_call/3

handle_info/2
let’s
talk
later...
9

gen_server
Container
gen_server:start_link/4

init/1

gen_server:call/2

handle_call/3

gen_server:cast/2

handle_cast/2

10

What’s
Calls
What,
Where?
?MODULE:store()
-‐>
gen_server:call/2

Client
process

Dispatch
to
impl
?MODULE:handle_call/3
gen_server
container
11

Documenta2on
-‐
EDoc

%%%
File
Scope
@author
@copyright

%%
Func+on
Scope
@doc
@spec
|
-‐spec
@end

12

Laying-‐Out
a
Module

{
%%%-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐

%%%
@author
Mar,n
Logan
<mar,njlogan@Macintosh.local>

%%%
@copyright
(C)
2010,
Mar,n
Logan

Header %%%
@doc

%%%

%%%
@end

%%%
Created
:
15
Sep
2010
by
Mar,n
Logan
<mar,njlogan@Macintosh.local>

%%%-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐

-‐module(ex4).

%%
API

-‐export([]).

{
%%%===================================================================

%%%
API

%%%===================================================================

API %%-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐

%%
@doc

my
func,on.

%%
@end

%%-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐

-‐spec
my_func(term)
-‐>
ok.

{
%%%===================================================================

Internal %%%
Internal
func,ons

%%%===================================================================

13

TCP
Basics

Server
1.
Bind
2.
Listen} gen_tcp:listen/2

3.
Accept gen_tcp:accept/1
4.
Send/Recv gen_tcp:send/1
handle_info/2
Client
1.
Connect gen_tcp:connect/2

2.
Send/Recv gen_tcp:send/1
handle_info/2

14

Our
TCP
Handling
gen_server

tcp_rpc/src/tr_server.erl

Tes2ng
the
Server

$ erl –pa tcp_rpc/ebin
Eshell V5.5.5 (abort with ^G)
1> {ok, LSock} = gen_tcp:listen(8080, [{active, true}, {reuseaddr, true}]).
…
2> tr_server:start_link(LSock).
…

From
your
standard
command
line
(bash,
sh,
etc...):

$? telnet localhost 8080
> io_lib:format(“~p ~p~n”, [hello, tr_server]).

Applica2ons

Ac+ve Library

Applica2on
Metadata

%% -*- mode: Erlang; fill-column: 75; comment-column: 50; -*-

{application, tcp_rpc,
[{description, "RPC server for Erlang and OTP in action"},
{vsn, "0.1.0"},
{modules, [tr_app,
tr_sup,
tr_server]},
{registered, [tr_sup]},
{applications, [kernel, stdlib]},
{mod, {tr_app, []}}
]}.

Applica2on
Behavior

tcp_rpc/src/tr_app.erl

Applica2on
is
also
a
Behaviour

• Interface
start/2,
stop/1
• Implementa2on
tr_app.erl
• Container
applica2on.erl
• Container
has
a
one
to
many
process

architecture.

22

Supervisor
Behaviour

tcp_rpc/src/tr_sup.erl

1.
tr_app
needs
to
start
this
top
level
supervisor

tcp_rpc
and
a
Concurrent
Server
“the
Erlang/OTP
way”

Parent

spawn
spawn
accept
tcp

request
for
new
tr_server

tr_server tr_server
wai+ng
to
accept

27

Star2ng
The
App

$ erl –pa tcp_rpc/ebin
Eshell V5.5.5 (abort with ^G)
1> application:start(sasl).
…
2> application:start(tcp_rpc).
…
3> appmon:start().

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