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Erlang cowboy 入门参考
http://blog.csdn.net/ubuntu64fan/article/details/40542549
本文翻译自:
http://ninenines.eu/docs/en/cowboy/HEAD/guide/getting_started/
我没有按原文逐句翻译。仅仅是我自己的理解,力求简单明了。本文程序在RHEL6.4上写成并运行,参考下面的文章,安装Erlang:
erlang在redhat上的安装
1 引言
Erlang不仅仅是一门语言,更是一个操作平台。Erlang开发者很少写单独的模块,而是写库和程序,然后把它们打包在一起进行发布。一个产品发布包含Erlang虚拟机和所有用来运行的程序,因此可以直接成为产品。Cowboy是Erlang编写的WebServer,提供Http,Https,WebSocket,TCP等各种高性能服务框架。本文将说明如何安装Cowboy,写第一个程序并发布。通过阅读本文,读者可以了解发布你的第一个Cowboy程序的全部内容。
2 开始第一个产品
当我们要开发一个程序(产品),我们希望用一个工程去管理它。代码构建,打包,发布等一系列行为。做Java开发使用的是Eclipse+Maven+Ant等工具。做Erlang开发可以使用Gnu Make。由于每个工具所完成的功能都类似,因此推荐使用下面这个Make模板。
https://github.com/ninenines/erlang.mk
下面开始我们的第一个Erlang工程。创建一个hello_erlang的目录,进入这个目录:
- $ mkdir hello_erlang && cd hello_erlang
下载erlang.mk文件。这是erlang工程的构建脚本。关于这个脚本的细节可以在各位成为erlang专家的时候去理解。
- $ wget --no-check-certificate https://raw.githubusercontent.com/ninenines/erlang.mk/master/erlang.mk
之后我们会看到目录下多了一个文件:erlang.mk。然后我们就可以生成我们的程序,同时生成发布版本(bootstrap,bootstrap-rel是target):
- $ make -f erlang.mk bootstrap bootstrap-rel
现在就可以构建我们的工程,生成发布版本:
- $ make
这个命令会花费较长时间执行完毕。然后启动运行产品程序:
- $ ./_rel/hello_erlang_release/bin/hello_erlang_release console
输入下面的命令可以看到运行的进程,其中包括:hello_erlang_sup
。这个是我们的程序的督程(supervisor)。
- (hello_erlang@127.0.0.1)1> i().
现在这个程序什么也没做,接下来我们给它添加Cowboy依赖,然后把它变成一个简单的HelloWorld程序。整个过程就是如下样子:
- [root@rhel64-origin workspace]# mkdir hello_erlang
- [root@rhel64-origin workspace]# cd hello_erlang/
- [root@rhel64-origin hello_erlang]# ls
- [root@rhel64-origin hello_erlang]# wget --no-check-certificate https://raw.githubusercontent.com/ninenines/erlang.mk/master/erlang.mk
- --2014-10-28 17:42:55-- https://raw.githubusercontent.com/ninenines/erlang.mk/master/erlang.mk
- Resolving raw.githubusercontent.com... 103.245.222.133
- Connecting to raw.githubusercontent.com|103.245.222.133|:443... connected.
- WARNING: certificate common name “www.github.com” doesn’t match requested host name “raw.githubusercontent.com”.
- HTTP request sent, awaiting response... 200 OK
- Length: 20522 (20K) [text/plain]
- Saving to: “erlang.mk”
- 100%[======================================================>] 20,522 --.-K/s in 0.04s
- 2014-10-28 17:42:55 (473 KB/s) - “erlang.mk” saved [20522/20522]
- [root@rhel64-origin hello_erlang]# ls
- erlang.mk
- [root@rhel64-origin hello_erlang]# make -f erlang.mk bootstrap bootstrap-rel
- [root@rhel64-origin hello_erlang]# make
- ERLC hello_erlang_app.erl hello_erlang_sup.erl
- APP hello_erlang.app.src
- GEN distclean-relx-rel
- --2014-10-28 17:43:08-- https://github.com/erlware/relx/releases/download/v1.0.2/relx
- Resolving github.com... 192.30.252.131
- Connecting to github.com|192.30.252.131|:443... connected.
- HTTP request sent, awaiting response... 302 Found
- Location: https://s3.amazonaws.com/github-cloud/releases/9900098/f6fcb596-e38d-11e3-9e8b-c953e4c1e42a?response-content-disposition=attachment%3B%20filename%3Drelx&response-content-type=application/octet-stream&AWSAccessKeyId=AKIAISTNZFOVBIJMK3TQ&Expires=1414489636&Signature=adyKnn8IPqauqWSnsXhJTc2vBio%3D [following]
- --2014-10-28 17:43:12-- https://s3.amazonaws.com/github-cloud/releases/9900098/f6fcb596-e38d-11e3-9e8b-c953e4c1e42a?response-content-disposition=attachment%3B%20filename%3Drelx&response-content-type=application/octet-stream&AWSAccessKeyId=AKIAISTNZFOVBIJMK3TQ&Expires=1414489636&Signature=adyKnn8IPqauqWSnsXhJTc2vBio%3D
- Resolving s3.amazonaws.com... 54.231.244.0
- Connecting to s3.amazonaws.com|54.231.244.0|:443... connected.
- HTTP request sent, awaiting response... 200 OK
- Length: 743699 (726K) [application/octet-stream]
- Saving to: “/root/workspace/hello_erlang/relx”
- 100%[======================================================>] 743,699 147K/s in 5.0s
- 2014-10-28 17:43:19 (145 KB/s) - “/root/workspace/hello_erlang/relx” saved [743699/743699]
- ===> Starting relx build process ...
- ===> Resolving OTP Applications from directories:
- /root/workspace/hello_erlang/ebin
- /usr/local/lib/erlang/lib
- ===> Resolving available OTP Releases from directories:
- /root/workspace/hello_erlang/ebin
- /usr/local/lib/erlang/lib
- ===> Resolved hello_erlang_release-1
- ===> Including Erts from /usr/local/lib/erlang
- ===> release successfully created!
3 cowboy安装
为了使我们的hello_erlang使用cowboy,我们需要修改2个文件:Makefile和src/hello_erlang.app.src。修改后的Makefile如下:
- PROJECT = hello_erlang
- DEPS = cowboy
- include erlang.mk
我们在src/hello_erlang.app.src文件中添加cowboy,这让我们的程序发布时自动将cowboy打包。有些仅仅是开发阶段的依赖不必要添加在这里(applications[...])。修改后的文件如下:
- {application, hello_erlang, [
- {description, "Hello Erlang!"},
- {vsn, "0.1.0"},
- {modules, []},
- {registered, []},
- {applications, [
- kernel,
- stdlib,
- cowboy
- ]},
- {mod, {hello_erlang_app, []}},
- {env, []}
- ]}.
现在我们运行make命令,cowboy就被自动加入到产品中,当然它什么也没做。输出如下:
- [root@rhel64-origin hello_erlang]# make
- --2014-10-28 17:53:58-- https://raw.githubusercontent.com/ninenines/erlang.mk/master/packages.v2.tsv
- Resolving raw.githubusercontent.com... 103.245.222.133
- Connecting to raw.githubusercontent.com|103.245.222.133|:443... connected.
- WARNING: certificate common name “www.github.com” doesn’t match requested host name “raw.githubusercontent.com”.
- HTTP request sent, awaiting response... 200 OK
- Length: 7115 (6.9K) [text/plain]
- Saving to: “/root/workspace/hello_erlang/.erlang.mk.packages.v2”
- 100%[======================================================>] 7,115 --.-K/s in 0.001s
- 2014-10-28 17:54:06 (12.6 MB/s) - “/root/workspace/hello_erlang/.erlang.mk.packages.v2” saved [7115/7115]
- Initialized empty Git repository in /root/workspace/hello_erlang/deps/cowboy/.git/
- remote: Counting objects: 7063, done.
- remote: Total 7063 (delta 0), reused 0 (delta 0)
- Receiving objects: 100% (7063/7063), 5.26 MiB | 530 KiB/s, done.
- Resolving deltas: 100% (4198/4198), done.
- make[1]: Entering directory `/root/workspace/hello_erlang/deps/cowboy‘
- DEPPKG=$(awk ‘BEGIN { FS = "\t" }; $1 == "cowlib" { print $2 " " $3 " " $4 }‘ /root/workspace/hello_erlang/.erlang.mk.packages.v2;) VS=$(echo $DEPPKG | cut -d " " -f1); REPO=$(echo $DEPPKG | cut -d " " -f2); COMMIT=$(echo $DEPPKG | cut -d " " -f3); if [ "$VS" = "git" ]; then git clone -n -- $REPO /root/workspace/hello_erlang/deps/cowlib; cd /root/workspace/hello_erlang/deps/cowlib && git checkout -q $COMMIT; else exit 78; fi
- Initialized empty Git repository in /root/workspace/hello_erlang/deps/cowlib/.git/
- remote: Counting objects: 202, done.
- remote: Total 202 (delta 0), reused 0 (delta 0)
- Receiving objects: 100% (202/202), 87.64 KiB | 100 KiB/s, done.
- Resolving deltas: 100% (119/119), done.
- DEPPKG=$(awk ‘BEGIN { FS = "\t" }; $1 == "ranch" { print $2 " " $3 " " $4 }‘ /root/workspace/hello_erlang/.erlang.mk.packages.v2;) VS=$(echo $DEPPKG | cut -d " " -f1); REPO=$(echo $DEPPKG | cut -d " " -f2); COMMIT=$(echo $DEPPKG | cut -d " " -f3); if [ "$VS" = "git" ]; then git clone -n -- $REPO /root/workspace/hello_erlang/deps/ranch; cd /root/workspace/hello_erlang/deps/ranch && git checkout -q $COMMIT; else exit 78; fi
- Initialized empty Git repository in /root/workspace/hello_erlang/deps/ranch/.git/
- remote: Counting objects: 905, done.
- Receiving objects: 100% (905/905), 288.85 KiB | 170 KiB/s, done.
- remote: Total 905 (delta 0), reused 0 (delta 0)
- Resolving deltas: 100% (532/532), done.
- make[2]: Entering directory `/root/workspace/hello_erlang/deps/cowlib‘
- ERLC cow_http_te.erl cow_http.erl cow_http_hd.erl cow_date.erl cow_mimetypes.erl cow_multipart.erl cow_qs.erl cow_cookie.erl cow_spdy.erl
- APP cowlib.app.src
- make[2]: Leaving directory `/root/workspace/hello_erlang/deps/cowlib‘
- make[2]: Entering directory `/root/workspace/hello_erlang/deps/ranch‘
- ERLC ranch_acceptors_sup.erl ranch_conns_sup.erl ranch_server.erl ranch_tcp.erl ranch.erl ranch_acceptor.erl ranch_listener_sup.erl ranch_app.erl ranch_protocol.erl ranch_ssl.erl ranch_sup.erl ranch_transport.erl
- APP ranch.app.src
- make[2]: Leaving directory `/root/workspace/hello_erlang/deps/ranch‘
- ERLC cowboy_router.erl cowboy_rest.erl cowboy_http_handler.erl cowboy_sup.erl cowboy_websocket_handler.erl cowboy_static.erl cowboy_sub_protocol.erl cowboy_websocket.erl cowboy.erl cowboy_app.erl cowboy_handler.erl cowboy_loop_handler.erl cowboy_protocol.erl cowboy_bstr.erl cowboy_clock.erl cowboy_http.erl cowboy_spdy.erl cowboy_req.erl cowboy_middleware.erl
- APP cowboy.app.src
- make[1]: Leaving directory `/root/workspace/hello_erlang/deps/cowboy‘
- APP hello_erlang.app.src
- GEN distclean-relx-rel
- ===> Starting relx build process ...
- ===> Resolving OTP Applications from directories:
- /root/workspace/hello_erlang/ebin
- /root/workspace/hello_erlang/deps
- /usr/local/lib/erlang/lib
- ===> Resolving available OTP Releases from directories:
- /root/workspace/hello_erlang/ebin
- /root/workspace/hello_erlang/deps
- /usr/local/lib/erlang/lib
- ===> Resolved hello_erlang_release-1
- ===> Including Erts from /usr/local/lib/erlang
- ===> release successfully created!
4 监听连接
当一个客户端请求到来,我们需要根据请求内容将请求分发(dispatch)到处理器(handler)。因此我们需要一个路由表(dispatch list),cowboy根据路由表分发请求到对应的处理模块程序。然后我们让cowboy开始监听连接。
编辑Erlang程序源代码文件:src/hello_erlang_app.erl,修改start/2函数,最后的src/hello_erlang_app.erl如下:
- -module(hello_erlang_app).
- -behaviour(application).
- -export([start/2]).
- -export([stop/1]).
- start(_Type, _Args) ->
- Dispatch = cowboy_router:compile([
- {‘_‘, [{"/", hello_handler, []}]}
- ]),
- cowboy:start_http(my_http_listener, 100, [{port, 8080}],
- [{env, [{dispatch, Dispatch}]}]
- ),
- hello_erlang_sup:start_link().
- stop(_State) ->
- ok.
现在我们把根路由"/"定义到hello_handler,下面我们就需要为此写这个处理器。
5 处理请求
cowboy具有处理各种请求的特色,例如:REST,WebSocket等。这里我们使用一个简单的HTTP处理器。我们使用处理器模板生成这个处理器:
- $ make new t=cowboy_http n=hello_handler
这将创建src/hello_handler.erl代码文件。打开它,修改成下面的样子(只修改了init/3):
- -module(hello_handler).
- -behaviour(cowboy_http_handler).
- -export([init/3]).
- -export([handle/2]).
- -export([terminate/3]).
- -record(state, {
- }).
- init(_, Req, Opts) ->
- Req2 = cowboy_req:reply(200,
- [{<<"content-type">>, <<"text/plain">>}],
- <<"Hello Erlang!">>,
- Req),
- {ok, Req2, Opts}.
- handle(Req, State=#state{}) ->
- {ok, Req2} = cowboy_req:reply(200, Req),
- {ok, Req2, State}.
- terminate(_Reason, _Req, _State) ->
- ok.
6 构建并运行
- $ make
- $ ./_rel/hello_erlang_release/bin/hello_erlang_release console
在浏览器中打开:http://your-ip-addr:8080/,显示如下:
7 总结
cowboy这个框架和nodejs很像。erlang的语法有点生疏,但是erlang比nodejs不知道强多少倍。erlang是C写的,nodejs的底层是C++,可见多数C++写的产品最后都不如C写的,这是偶然么?“一只鸟长得像鸭子,叫声像鸭子,走路也像鸭子,那它就是鸭子!”
Erlang cowboy 入门参考