无意间发现yaml提供了一个特别有意思的功能：锚点（&）和别名（*）。可以使用它们来引用 yaml 中一些重复的配置。
yaml 配置如下：
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defaults: &defaults
adapter: postgres
host: localhost
development:
database: myapp_development
<<: *defaults
test:
database: myapp_test
<<: *defaults
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等同下面yaml配置：
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defaults:
adapter: postgres
host: localhost
development:
database: myapp_development
adapter: postgres
host: localhost
test:
database: myapp_test
adapter: postgres
host: localhost
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& 用来建立锚点（defaults），<< 表示合并到当前数据，* 用来引用锚点。
我将这一功能应用到docker-compose文件，省去了大量重复配置，使得 docker-compose 文件更为精炼：
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x-templates:
agent_centos8_aarch64: &agent_centos8_aarch64
image: harbor.einscat.com:10011/library/centos8:aarch64
privileged: true
stdin_open: true
tty: true
extra_hosts:
- "docker-registry:192.168.18.20"
cap_add:
- ALL
working_dir: /opt
volumes:
- /sys/fs/cgroup:/sys/fs/cgroup:rw
services:
vm-1:
container_name: vm-1
hostname: "vm-1"
networks:
vm_net:
ipv4_address: 172.20.30.1
vm_net_2:
ipv4_address: 172.20.40.1
ports:
- "3306:3306"
volumes:
- "/sys/fs/cgroup:/sys/fs/cgroup:rw"
- "~/workspace:/root/workspace"
<<: *agent_centos8_aarch64
vm-2:
container_name: vm-2
hostname: "vm-2"
networks:
vm_net:
ipv4_address: 172.20.30.2
vm_net_2:
ipv4_address: 172.20.40.2
ports:
- "3307:3306"
- "6380:6379"
<<: *agent_centos8_aarch64
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参考
