Consul-Template

Consul-Template简介

Consul-Template是基于Consul的自动替换配置文件的应用。在Consul-Template没出现之前，大家构建服务发现系统大多采用的是Zookeeper、Etcd+Confd这样类似的系统。

Consul官方推出了自己的模板系统Consul-Template后，动态的配置系统可以分化为Etcd+Confd和Consul+Consul-Template两大阵营。Consul-Template的定位和Confd差不多，Confd的后端可以是Etcd或者Consul。

Consul-Template提供了一个便捷的方式从Consul中获取存储的值，Consul-Template守护进程会查询Consul实例来更新系统上指定的任何模板。当更新完成后，模板还可以选择运行一些任意的命令。

 

Consul-Template的使用场景

Consul-Template可以查询Consul中的服务目录、Key、Key-values等。这种强大的抽象功能和查询语言模板可以使Consul-Template特别适合动态的创建配置文件。例如：创建Apache/Nginx Proxy Balancers、Haproxy Backends、Varnish Servers、Application Configurations等。

Consul-Template特性

• Quiescence：Consul-Template内置静止平衡功能，可以智能的发现Consul实例中的更改信息。这个功能可以防止频繁的更新模板而引起系统的波动。
• Dry Mode：不确定当前架构的状态，担心模板的变化会破坏子系统？无须担心。因为Consul-Template还有Dry模式。在Dry模式，Consul-Template会将结果呈现在STDOUT，所以操作员可以检查输出是否正常，以决定更换模板是否安全。
• CLI and Config：Consul-Template同时支持命令行和配置文件。
• Verbose Debugging：即使每件事你都做的近乎完美，但是有时候还是会有失败发生。Consul-Template可以提供更详细的Debug日志信息。

项目地址：https://github.com/hashicorp/consul-template

Consul-Template安装

Consul-Template和Consul一样，也是用Golang实现。因此具有天然可移植性(支持 Linux、windows 和macOS)。安装包仅包含一个可执行文件。Consul-Template安装非常简单，只需要下载对应系统的软件包并解压后就可使用。

这里以Linux系统为例：

 

1 $ wget https://releases.hashicorp.com/consul-template/0.18.3/consul-template_0.18.3_linux_amd64.zip
2 $ unzip consul-template_0.18.3_linux_amd64.zip
3 $ mv consul-template /usr/local/bin/

 

其它系统版本可在这里下载：https://releases.hashicorp.com/consul-template/

Consul-Template常用命令

  1 $ consul-template -h
  2 
  3 Usage: consul-template [options]
  4 
  5   Watches a series of templates on the file system, writing new changes when
  6   Consul is updated. It runs until an interrupt is received unless the -once
  7   flag is specified.
  8 
  9 Options:
 10 
 11   -config=
 12       Sets the path to a configuration file or folder on disk. This can be
 13       specified multiple times to load multiple files or folders. If multiple
 14       values are given, they are merged left-to-right, and CLI arguments take
 15       the top-most precedence.
 16 
 17   -consul-addr=

 18       Sets the address of the Consul instance
 19 
 20   -consul-auth=
 21       Set the basic authentication username and password for communicating
 22       with Consul.
 23 
 24   -consul-retry
 25       Use retry logic when communication with Consul fails
 26 
 27   -consul-retry-attempts=
 28       The number of attempts to use when retrying failed communications
 29 
 30   -consul-retry-backoff=
 31       The base amount to use for the backoff duration. This number will be
 32       increased exponentially for each retry attempt.
 33 
 34   -consul-ssl
 35       Use SSL when connecting to Consul
 36 
 37   -consul-ssl-ca-cert=
 38       Validate server certificate against this CA certificate file list
 39 
 40   -consul-ssl-ca-path=
 41       Sets the path to the CA to use for TLS verification
 42 
 43   -consul-ssl-cert=
 44       SSL client certificate to send to server
 45 
 46   -consul-ssl-key=
 47       SSL/TLS private key for use in client authentication key exchange
 48 
 49   -consul-ssl-server-name=
 50       Sets the name of the server to use when validating TLS.
 51 
 52   -consul-ssl-verify
 53       Verify certificates when connecting via SSL
 54 
 55   -consul-token=
 56       Sets the Consul API token
 57 
 58   -consul-transport-dial-keep-alive=
 59       Sets the amount of time to use for keep-alives
 60 
 61   -consul-transport-dial-timeout=
 62       Sets the amount of time to wait to establish a connection
 63 
 64   -consul-transport-disable-keep-alives
 65       Disables keep-alives (this will impact performance)
 66 
 67   -consul-transport-max-idle-conns-per-host=
 68       Sets the maximum number of idle connections to permit per host
 69 
 70   -consul-transport-tls-handshake-timeout=
 71       Sets the handshake timeout
 72 
 73   -dedup
 74       Enable de-duplication mode - reduces load on Consul when many instances of
 75       Consul Template are rendering a common template
 76 
 77   -dry
 78       Print generated templates to stdout instead of rendering
 79 
 80   -exec=
 81       Enable exec mode to run as a supervisor-like process - the given command
 82       will receive all signals provided to the parent process and will receive a
 83       signal when templates change
 84 
 85   -exec-kill-signal=
 86       Signal to send when gracefully killing the process
 87 
 88   -exec-kill-timeout=
 89       Amount of time to wait before force-killing the child
 90 
 91   -exec-reload-signal=
 92       Signal to send when a reload takes place
 93 
 94   -exec-splay=
 95       Amount of time to wait before sending signals
 96 
 97   -kill-signal=
 98       Signal to listen to gracefully terminate the process
 99 
100   -log-level=
101       Set the logging level - values are "debug", "info", "warn", and "err"
102 
103   -max-stale=
104       Set the maximum staleness and allow stale queries to Consul which will
105       distribute work among all servers instead of just the leader
106 
107   -once
108       Do not run the process as a daemon
109 
110   -pid-file=
111       Path on disk to write the PID of the process
112 
113   -reload-signal=
114       Signal to listen to reload configuration
115 
116   -retry=
117       The amount of time to wait if Consul returns an error when communicating
118       with the API
119 
120   -syslog
121       Send the output to syslog instead of standard error and standard out. The
122       syslog facility defaults to LOCAL0 and can be changed using a
123       configuration file
124 
125   -syslog-facility=
126       Set the facility where syslog should log - if this attribute is supplied,
127       the -syslog flag must also be supplied
128 
129   -template=