关于confd是什么？

     他是一个可以在etcd和consul的基础上实现配置管理的工具。 etcd和consul在功能上是有些重叠的，所以咱们就拿etcd来测试吧。

再简单来描述下conf，他是可以从etcd里面获取kv数据，然后通过咱们提前定制的模板，渲染配置文件。。。。  然后可以check_md 和 reload_md

文章本来在github看到的，自己又重新加了点料。

https://github.com/kelseyhightower/confd/blob/master/docs/quick-start-guide.md

首先增加keys关键字，我这边是测试，所以用的时etcdctl客户端，做实际应用还是推荐用python的etcd客户端。 

etcdctl set /myapp/database/url db.example.com
etcdctl set /myapp/database/user rob

Create the confdir

创建配置目录及模板的目录

sudo mkdir -p /etc/confd/{conf.d,templates}

Create a template resource config

文件的后缀要有.toml  ，这个也算个规范吧 。  toml本身也是个配置的数据类型，有点像configparse和yaml似的。 

[template]
src = "myconfig.conf.tmpl"
dest = "/tmp/myconfig.conf"
keys = [
    "/myapp/database/url",
    "/myapp/database/user",
]

Create the source template

创建动态的模板，里面需要有可以获取key的动态逻辑。

/etc/confd/templates/myconfig.conf.tmpl

[myconfig]
database_url = {{getv "/myapp/database/url"}}
database_user = {{getv "/myapp/database/user"}}

Process the template

调用confd命令来获取，backend是指明客户端，下面用的时etcd

confd -onetime -backend etcd -node 127.0.0.1:4001

然后执行后的结果是：

2014-07-08T20:38:36-07:00 confd[16252]: WARNING Skipping confd config file.
2014-07-08T20:38:36-07:00 confd[16252]: INFO Target config /tmp/myconfig.conf out of sync
2014-07-08T20:38:36-07:00 confd[16252]: INFO Target config /tmp/myconfig.conf has been updated

那么下载出来的配置文件是这个样子

cat /tmp/myconfig.conf

# This a comment
[myconfig]
database_url = db.example.com
database_user = rob

Advanced Example

etcdctl set /myapp/subdomain myapp
etcdctl set /myapp/upstream/app2 "10.0.1.100:80"
etcdctl set /myapp/upstream/app1 "10.0.1.101:80"
etcdctl set /yourapp/subdomain yourapp
etcdctl set /yourapp/upstream/app2 "10.0.1.102:80"
etcdctl set /yourapp/upstream/app1 "10.0.1.103:80"

Create template resources

/etc/confd/conf.d/myapp-nginx.toml

[template]
prefix = "/myapp"
src = "nginx.tmpl"
dest = "/tmp/myapp.conf"
owner = "nginx"
mode = "0644"
keys = [
  "/subdomain",
  "/upstream",
]
check_cmd = "/usr/sbin/nginx -t -c {{.src}}"
reload_cmd = "/usr/sbin/service nginx reload"

/etc/confd/conf.d/yourapp-nginx.toml

[template]
prefix = "/yourapp"
src = "nginx.tmpl"
dest = "/tmp/yourapp.conf"
owner = "nginx"
mode = "0644"
keys = [
  "/subdomain",
  "/upstream",
]
check_cmd = "/usr/sbin/nginx -t -c {{.src}}"
reload_cmd = "/usr/sbin/service nginx reload"

Create the source template

/etc/confd/templates/nginx.tmpl

upstream {{getv "/subdomain"}} {
{{range getvs "/upstream/*"}}
    server {{.}};
{{end}}
}

server {
    server_name  {{getv "/subdomain"}}.example.com;
    location / {
        proxy_pass        http://{{getv "/subdomain"}};
        proxy_redirect    off;
        proxy_set_header  Host             host;
        proxy_set_header  X-Real-IPremote_addr;
        proxy_set_header  X-Forwarded-For  $proxy_add_x_forwarded_for;
   }
}

confd etcd 是在一个老外的博客看到的，本来也想把地址给贴上来，但是找不到了。  

confd也是个有趣的应用，他其实就是简化了自己关于管理配置和模板开发，但是问题来了， 我是个pythoner程序员，对于python的第三方的模板  jinja2 mako 是相当的熟悉，但是如果学习confd的话，我还需要学习confd自己特定的语法。 这有些不效率了了。

这里再贴下 confd对于模板渲染的语法，貌似没有for这个函数，然后还缺少自定义函数的功能，这个让我很是蛋疼。 

exists

如果这个key在etcd定义了的话？

{{if exists "/key"}}
    value: {{getv "/key"}}
{{end}}

get

如果这个key没有，他不会返回一个error

{{with get "/key"}}
    key: {{.Key}}
    value: {{.Value}}
{{end}}

gets

Returns all KVPair, []KVPair, where key matches its argument. Returns an error if key is not found.

{{range gets "/*"}}
    key: {{.Key}}
    value: {{.Value}}
{{end}}

getv

Returns the value as a string where key matches its argument. Returns an error if key is not found.

value: {{getv "/key"}}

getvs

Returns all values, []string, where key matches its argument. Returns an error if key is not found.

{{range getvs "/*"}}
    value: {{.}}
{{end}}

datetime

Alias for time.Now

# Generated by confd {{datetime}}

Outputs:

# Generated by confd 2015-01-23 13:34:56.093250283 -0800 PST

# Generated by confd {datetime.Format("Jan 2, 2006 at 3:04pm (MST)")}

Outputs:

# Generated by confd Jan 23, 2015 at 1:34pm (EST)

See the time package for more usage: http://golang.org/pkg/time/

split

可以对于一条数据进行自定义切分，splite

{{ url := split (getv "/deis/service") ":" }}
    host: {{indexurl 0}}
    port: {{index $url 1}}

json

Returns an map[string]interface{} of the json value.