2020年 · Linux · 点滴记录

confd template src格式和 templates 语法

Template Resources

Template resources are written in TOML and define a single template resource. Template resources are stored under the/etc/confd/conf.d directory by default.

Required

  • dest (string) – The target file.
  • keys (array of strings) – An array of keys.
  • src (string) – The relative path of a configuration template.

Optional

  • gid (int) – The gid that should own the file. Defaults to the effective gid.
  • mode (string) – The permission mode of the file.
  • uid (int) – The uid that should own the file. Defaults to the effective uid.
  • reload_cmd (string) – The command to reload config.
  • check_cmd (string) – The command to check config. Use {{.src}} to reference the rendered source template.
  • prefix (string) – The string to prefix to keys.

Notes

When using the reload_cmd feature it’s important that the command exits on its own. The reload command is not managed by confd, and will block the configuration run until it exits.

Example

[template]
src = "nginx.conf.tmpl"
dest = "/etc/nginx/nginx.conf"
uid = 0
gid = 0
mode = "0644"
keys = [
  "/nginx",
]
check_cmd = "/usr/sbin/nginx -t -c {{.src}}"
reload_cmd = "/usr/sbin/service nginx restart"

Templates

Templates define a single application configuration template. Templates are stored under the /etc/confd/templates directory by default.

Templates are written in Go’s text/template.

Template Functions

map

creates a key-value map of string -> interface{}

  1. {{$endpoint := map “name” “elasticsearch” “private_port” 9200 “public_port” 443}}
  2. name: {{index $endpoint “name”}}
  3. private-port: {{index $endpoint “private_port”}}
  4. public-port: {{index $endpoint “public_port”}}

specifically useful if you a sub-template and you want to pass multiple values to it.

base

Alias for the path.Base function.

  1. {{with get “/key”}}
  2. key: {{base .Key}}
  3. value: {{.Value}}
  4. {{end}}

exists

Checks if the key exists. Return false if key is not found.

  1. {{if exists “/key”}}
  2. value: {{getv “/key”}}
  3. {{end}}

get

Returns the KVPair where key matches its argument. Returns an error if key is not found.

  1. {{with get “/key”}}
  2. key: {{.Key}}
  3. value: {{.Value}}
  4. {{end}}

gets

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

  1. {{range gets “/*”}}
  2. key: {{.Key}}
  3. value: {{.Value}}
  4. {{end}}

getv

Returns the value as a string where key matches its argument or an optional default value. Returns an error if key is not found and no default value given.

value: {{getv "/key"}}

With a default value

value: {{getv "/key" "default_value"}}

getvs

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

  1. {{range getvs “/*”}}
  2. value: {{.}}
  3. {{end}}

getenv

Wrapper for os.Getenv. Retrieves the value of the environment variable named by the key. It returns the value, which will be empty if the variable is not present. Optionally, you can give a default value that will be returned if the key is not present.

export HOSTNAME=`hostname`
hostname: {{getenv "HOSTNAME"}}

With a default value

ipaddr: {{getenv "HOST_IP" "127.0.0.1"}}

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

Wrapper for strings.Split. Splits the input string on the separating string and returns a slice of substrings.

  1. {{ $url := split (getv “/deis/service”) “:” }}
  2. host: {{index $url 0}}
  3. port: {{index $url 1}}

toUpper

Alias for strings.ToUpper Returns uppercased string.

key: {{toUpper "value"}}

toLower

Alias for strings.ToLower. Returns lowercased string.

key: {{toLower "Value"}}

json

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

lookupSRV

Wrapper for net.LookupSRV. The wrapper also sorts the SRV records alphabetically by combining all the fields of the net.SRV struct to reduce unnecessary config reloads.

  1. {{range lookupSRV “mail” “tcp” “example.com”}}
  2. target: {{.Target}}
  3. port: {{.Port}}
  4. priority: {{.Priority}}
  5. weight: {{.Weight}}
  6. {{end}}

Add keys to etcd

  1. etcdctl set /services/zookeeper/host1 ‘{“Id”:“host1”, “IP”:“192.168.10.11”}’
  2. etcdctl set /services/zookeeper/host2 ‘{“Id”:“host2”, “IP”:“192.168.10.12”}’

Create the template resource

  1. [template]
  2. src = “services.conf.tmpl”
  3. dest = “/tmp/services.conf”
  4. keys = [
  5. “/services/zookeeper/”
  6. ]

Create the template

  1. {{range gets “/services/zookeeper/*”}}
  2. {{$data := json .Value}}
  3. id: {{$data.Id}}
  4. ip: {{$data.IP}}
  5. {{end}}

Advanced Map Traversals

Once you have parsed the JSON, it is possible to traverse it with normal Go template functions such as index.

A more advanced structure, like this:

  1. {
  2. “animals”: [
  3. {“type”: “dog”, “name”: “Fido”},
  4. {“type”: “cat”, “name”: “Misse”}
  5. ]
  6. }

It can be traversed like this:

  1. {{$data := json (getv “/test/data/”)}}
  2. type: {{ (index $data.animals 1).type }}
  3. name: {{ (index $data.animals 1).name }}
  4. {{range $data.animals}}
  5. {{.name}}
  6. {{end}}

jsonArray

Returns a []interface{} from a json array such as ["a", "b", "c"].

  1. {{range jsonArray (getv “/services/data/”)}}
  2. val: {{.}}
  3. {{end}}

ls

Returns all subkeys, []string, where path matches its argument. Returns an empty list if path is not found.

  1. {{range ls “/deis/services”}}
  2. value: {{.}}
  3. {{end}}

lsdir

Returns all subkeys, []string, where path matches its argument. It only returns subkeys that also have subkeys. Returns an empty list if path is not found.

  1. {{range lsdir “/deis/services”}}
  2. value: {{.}}
  3. {{end}}

dir

Returns the parent directory of a given key.

  1. {{with dir “/services/data/url”}}
  2. dir: {{.}}
  3. {{end}}

join

Alias for the strings.Join function.

  1. {{$services := getvs “/services/elasticsearch/*”}}
  2. services: {{join $services “,”}}

replace

Alias for the strings.Replace function.

  1. {{$backend := getv “/services/backend/nginx”}}
  2. backend = {{replace $backend “-“ “_” -1}}

lookupIP

Wrapper for net.LookupIP function. The wrapper also sorts (alphabeticaly) the IP addresses. This is crucial since in dynamic environments DNS servers typically shuffle the addresses linked to domain name. And that would cause unnecessary config reloads.

  1. {{range lookupIP “some.host.local”}}
  2. server {{.}};
  3. {{end}}

Example Usage

etcdctl set /nginx/domain 'example.com'
etcdctl set /nginx/root '/var/www/example_dotcom'
etcdctl set /nginx/worker_processes '2'
etcdctl set /app/upstream/app1 "10.0.1.100:80"
etcdctl set /app/upstream/app2 "10.0.1.101:80"

/etc/confd/templates/nginx.conf.tmpl

  1. worker_processes {{getv “/nginx/worker_processes”}};
  2. upstream app {
  3. {{range getvs “/app/upstream/*”}}
  4. server {{.}};
  5. {{end}}
  6. }
  7. server {
  8. listen 80;
  9. server_name www.{{getv “/nginx/domain”}};
  10. access_log /var/log/nginx/{{getv “/nginx/domain”}}.access.log;
  11. error_log /var/log/nginx/{{getv “/nginx/domain”}}.log;
  12. location / {
  13. root {{getv “/nginx/root”}};
  14. index index.html index.htm;
  15. proxy_pass http://app;
  16. proxy_redirect off;
  17. proxy_set_header Host $host;
  18. proxy_set_header X-Real-IP $remote_addr;
  19. proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  20. }
  21. }

Output: /etc/nginx/nginx.conf

  1.  worker_processes 2;
  2.  upstream app {
  3.  server 10.0.1.100:80;
  4.  server 10.0.1.101:80;
  5.  }
  6.  server {
  7.  listen 80;
  8.  server_name www.example.com;
  9.  access_log /var/log/nginx/example.com.access.log;
  10.  error_log /var/log/nginx/example.com.error.log;
  11.  location / {
  12.  root /var/www/example_dotcom;
  13.  index index.html index.htm;
  14.  proxy_pass http://app;
  15.  proxy_redirect off;
  16.  proxy_set_header Host $host;
  17.  proxy_set_header X-Real-IP $remote_addr;
  18.  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  19.  }
  20.  }

Complex example

This examples show how to use a combination of the templates functions to do nested iteration.

Add keys to etcd

  1.  etcdctl mkdir /services/web/cust1/
  2.  etcdctl mkdir /services/web/cust2/
  3.  etcdctl set /services/web/cust1/2 ‘{“IP”: “10.0.0.2”}’
  4.  etcdctl set /services/web/cust2/2 ‘{“IP”: “10.0.0.4”}’
  5.  etcdctl set /services/web/cust2/1 ‘{“IP”: “10.0.0.3”}’
  6.  etcdctl set /services/web/cust1/1 ‘{“IP”: “10.0.0.1”}’

Create the template resource

  1.  [template]
  2.  src = “services.conf.tmpl”
  3.  dest = “/tmp/services.conf”
  4.  keys = [
  5.  “/services/web”
  6.  ]

Create the template

  1.  {{range $dir := lsdir “/services/web”}}
  2.  upstream {{base $dir}} {
  3.  {{$custdir := printf “/services/web/%s/*” $dir}}{{range gets $custdir}}
  4.  server {{$data := json .Value}}{{$data.IP}}:80;
  5.  {{end}}
  6.  }
  7.  server {
  8.  server_name {{base $dir}}.example.com;
  9.  location / {
  10.  proxy_pass {{base $dir}};
  11.  }
  12.  }
  13.  {{end}}

Output:/tmp/services.conf

  1.  upstream cust1 {
  2.  server 10.0.0.1:80;
  3.  server 10.0.0.2:80;
  4.  }
  5.  server {
  6.  server_name cust1.example.com;
  7.  location / {
  8.  proxy_pass cust1;
  9.  }
  10.  }
  11.  upstream cust2 {
  12.  server 10.0.0.3:80;
  13.  server 10.0.0.4:80;
  14.  }
  15.  server {
  16.  server_name cust2.example.com;
  17.  location / {
  18.  proxy_pass cust2;
  19.  }
  20.  }