Confid+etcd to realize automatic discovery of high availability

Confd What is it?

Confd Is a lightweight configuration management tool . By querying backend storage , Combined with the configuration template engine , Keep local configuration up to date , At the same time, it has regular detection mechanism , Configuration changes automatically reload. The corresponding back-end storage can be etcd,redis、zookeeper wait We use etcd Demonstrate for the back end confd Use , Teach you how to generate configuration dynamically in the simplest and rudimentary way

One . Get ready confd Dependent storage etcd

etcd -listen-client-urls="http://0.0.0.0:2379" --advertise-client-urls="http://0.0.0.0:2379" &

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etcd Build if you can't see the previous article 《 Build from scratch etcd Distributed The storage system +web Management interface 》

Two . install confd

#  download 
wget https://github.com/kelseyhightower/confd/releases/download/v0.16.0/confd-0.16.0-linux-amd64

#  install 
mv confd-0.16.0-linux-amd64 /usr/local/bin/confd
chmod +x /usr/local/bin/confd

# Check if the installation is successful 
[email protected]:/home/chenqionghe/test/confd# confd --version
confd 0.16.0 (Git SHA: 7217b0ca, Go Version: go1.10.2)

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• confd The default configuration file is /etc/confd in , You can use the parameter -confdir Appoint . The directory contains two subdirectories , Namely ：conf.d templates.
• confd Read first conf.d The configuration file in the directory (toml Format ), Then render the template according to the template path specified by the file , Re execution <RELOAD_CMD>.

Let's create

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

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confd Configuration file for , It mainly includes the generation logic of configuration , For example, template source , Back end storage corresponds to keys, Order execution, etc . templates: The configuration template Template, That is, configuration based on different components , It is amended as follows go Language template file .

3、 ... and . Configuration and use confd

1. create profile /etc/confd/conf.d/chenqionghe.toml

[template]
#  Template file path 
src = "https://www.linuxidc.com/Linux/2019-03/chenqionghe.tmpl"
#  Generate final file path 
dest = "/home/chenqionghe/test/confd/gym-data.txt"
keys = [
    "/chenqionghe/deap_squat",
    "/chenqionghe/bench_press",
    "/chenqionghe/dead_lift",
]
#  Command executed after generating file 
reload_cmd = "echo 'light weight baby' >> /home/chenqionghe/test/confd/reaload.txt"

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2. Create template file /etc/confd/templates/chenqionghe.tmpl

[ Chen qionghe ]
 Squat down  = {{getv "/chenqionghe/deap_squat"}}
 Oh my god  = {{getv "/chenqionghe/bench_press"}}
 Hard drawn  = {{getv "/chenqionghe/dead_lift"}}

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3. initialization etcd Data in

endpoints=http://127.0.0.1:2379
etcdctl --endpoints=$endpoints set /chenqionghe/deap_squat '130kg'
etcdctl --endpoints=$endpoints set /chenqionghe/bench_press '100kg'
etcdctl --endpoints=$endpoints set /chenqionghe/dead_lift '160kg'

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4. start-up confd Service for

confd Support with daemon perhaps onetime Two modes of operation onetime Pattern ： The configuration will only be generated once , after key No matter the change will not generate again

    confd -onetime -backend etcd -node http://127.0.0.1:2379

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• daemon Pattern ：confd It will monitor the configuration changes of back-end storage , Generate the target configuration file dynamically according to the configuration template .

confd Support with daemon perhaps onetime Two modes of operation

• daemon Pattern ：confd It will monitor the configuration changes of back-end storage , And dynamically generate the target configuration file according to the configuration template .

confd -watch -backend etcd -node http://127.0.0.1:2379 &

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We use daemon mode , Then change key Value , Observe file changes , You can see reload.txt Documents are being added continuously light weight baby

gym-data.txt Follow 3 individual key The changes are constantly updated

Four . About - Template syntax

confd The template used is go Linguistic template, Yes go Students who are familiar with the language should find it very simple confd A lot of template functions have been integrated , Reference link

5、 ... and . Think about expanding -confd What can be done

We probably know confd Principle 1. Read configuration file -> 2. Use the template to generate the specified file -> 3. Run overload command ( Optional )

So basically using configuration and reload The command can be used everywhere confd, Such as the demand below

• nginx Dynamic generation upstream Implementing service discovery
• prometheus Dynamic generation prometheus.yml Realize automatic alarm
• php-fpm Dynamic generation php.ini File to achieve dynamic performance tuning
• Dynamically generate report files and send notifications

Only unexpected , No, I can't , I thought about writing a nginx Dynamic generation of upstream, I didn't expect someone to write it out , It's really powerful , Guys, hurry up high Get up