Harbor新建目标时测试连接失败（no such host）

环境是下面这样，一共两台主机：

a.harbor.com（172.16.20.80） -----> b.harbor.com（172.16.20.81）

harbor版本：v2.5.5

搭建了两台harbor，准备实现双向复制，但是在a.harbor.com上新建目标时无法连接到b.harbor.com：

查看harbor-core的日志，日志显示无法解析主机：

$ docker logs -f harbor-core
2023-02-02T04:09:11Z [ERROR] [/lib/http/error.go:54]: {"errors":[{"code":"UNKNOWN","message":"unknown: Get \"https://b.harbor.com/api/version\": dial tcp: lookup b.harbor.com on 127.0.0.11:53: no such host"}]} 
2023-02-02T04:11:05Z [ERROR] [/lib/http/error.go:54]: {"errors":[{"code":"UNKNOWN","message":"unknown: Get \"https://b.harbor.com/api/version\": dial tcp: lookup b.harbor.com on 127.0.0.11:53: no such host"}]} 

原因就是harbor-core容器无法解析主机名。

$ docker exec -u root -it harbor-core ping b.harbor.com
ping: b.harbor.com: Name or service not known

在主机a.harbor.com的harbor-core容器中添加主机记录：

$ docker exec -u root -it harbor-core bash
root [ /harbor ]# echo "172.16.20.81 b.harbor.com" >> /etc/hosts
root [ /harbor ]# exit

同样，在主机b.harbor.com的harbor-core容器中也添加主机记录：

$ docker exec -u root -it harbor-core bash
root [ /harbor ]# echo "172.16.20.80 a.harbor.com" >> /etc/hosts
root [ /harbor ]# exit

再次在a.harbor.com上测试连接：

上面的方法只能临时解决问题，当容器重新启动后主机记录就会丢失。所以需要修改docker-compose持久化保存。

修改a.harbor.com的docker-compose.yml。extra_hosts的作用就是在容器的/etc/hosts中添加记录。

# 在harbor的工作目录下
# 停止容器
$ docker-compose down

# 修改docker-compose.yml文件,在core和jobservice的最后添加extra_hosts。格式和/etc/hosts是相反的。
# core对应harbor-core容器，jobservice对应harbor-jobservice容器
# harbor-jobservice负责镜像复制工作，如果不修改后续的复制会失败。
$ vim docker-compose.yml
  core:
    image: goharbor/harbor-core:v2.5.5
    container_name: harbor-core
    ... ...
    extra_hosts:
      - "a.harbor.com:172.16.20.80"
      - "b.harbor.com:172.16.20.81"
  jobservice:
    image: goharbor/harbor-jobservice:v2.5.5
    container_name: harbor-jobservice
    ... ...
    extra_hosts:
      - "a.harbor.com:172.16.20.80"
      - "b.harbor.com:172.16.20.81"

# 启动容器
$ docker-compose up -d

# 确认有刚才添加的主机记录
$ docker exec -u root -it harbor-core cat /etc/hosts
127.0.0.1	localhost
::1	localhost ip6-localhost ip6-loopback
fe00::0	ip6-localnet
ff00::0	ip6-mcastprefix
ff02::1	ip6-allnodes
ff02::2	ip6-allrouters
172.16.20.80	a.harbor.com
172.16.20.81	b.harbor.com
172.20.0.8	09f16e15e9be

在b.harbor.com上也修改docker-compose.yml：

$ vim docker-compose.yml
  core:
    image: goharbor/harbor-core:v2.5.5
    container_name: harbor-core
    ... ...
    extra_hosts:
      - "a.harbor.com:172.16.20.80"
      - "b.harbor.com:172.16.20.81"
  jobservice:
    image: goharbor/harbor-jobservice:v2.5.5
    container_name: harbor-jobservice
    ... ...
    extra_hosts:
      - "a.harbor.com:172.16.20.80"
      - "b.harbor.com:172.16.20.81"
      
# 确认有刚才添加的主机记录
$ docker exec -u root -it harbor-core cat /etc/hosts
127.0.0.1	localhost
::1	localhost ip6-localhost ip6-loopback
fe00::0	ip6-localnet
ff00::0	ip6-mcastprefix
ff02::1	ip6-allnodes
ff02::2	ip6-allrouters
172.16.20.80	a.harbor.com
172.16.20.81	b.harbor.com
172.18.0.8	de168afb1bac