python - Docker:当使用容器名称从一个容器连接到另一个容器时，如何修复 “could not translate host name ” postgres“寻址”？

Question

我开始3个容器:

docker run -d --rm --name redis    --publish 6379:6379 redis 
docker run -d --rm --name postgres --publish 5432:5432 -e POSTGRES_HOST_AUTH_METHOD=trust -e POSTGRES_DB=hi postgres:9.6
docker run -d --rm --name web      --publish 8000:8000 python:3.6.8-stretch sleep 1000

进行 docker ps显示:


然后我执行 web:

docker exec -it web bash

然后我安装 psycopg2:

$ pip install psycopg2

然后我尝试连接到 host: postgres， port:5432， database:hi:

我启动python:

$ python

然后我运行以下命令:

import psycopg2
conn = psycopg2.connect(host="postgres", port = 5432, database="hi", user="postgres", password=""

我收到以下错误:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.6/site-packages/psycopg2/__init__.py", line 127, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: could not translate host name "postgres" to address: Name or service not known

我认为这可能是docker网络问题，所以我去检查了一下，所有主机名都在那儿:

{
    "Name": "bridge",
    "Id": "8e37606d20ae80189da4d7ecdb7673274fa2e0c9dd2b5c2b4c3db4e545c1ef20",
    "Created": "2020-05-14T19:10:43.532158344Z",
    "Scope": "local",
    "Driver": "bridge",
    "EnableIPv6": false,
    "IPAM": {
        "Driver": "default",
        "Options": null,
        "Config": [
            {
                "Subnet": "172.17.0.0/16",
                "Gateway": "172.17.0.1"
            }
        ]
    },
    "Internal": false,
    "Attachable": false,
    "Ingress": false,
    "ConfigFrom": {
        "Network": ""
    },
    "ConfigOnly": false,
    "Containers": {
        "3bb2a6cf4fbb235324d335f238c20fe026e37bccc717d1cd0bd1df43e70dbec6": {
            "Name": "redis",
            "EndpointID": "f927fc2a199d033bbbc8ecc8ff1bccf508e607384e4820884f3236f11a961c04",
            "MacAddress": "02:42:ac:11:00:02",
            "IPv4Address": "172.17.0.2/16",
            "IPv6Address": ""
        },
        "545065d96fb6f867724ece2cf11881af26be9885f16212bef4260bccba00a2be": {
            "Name": "web",
            "EndpointID": "750133a6bb72e23929c57f32aa7776bc85d3dd255a16473a4afe230d0c6cb9c2",
            "MacAddress": "02:42:ac:11:00:04",
            "IPv4Address": "172.17.0.4/16",
            "IPv6Address": ""
        },
        "cfb2e556ca9f26ff8c7063f2347b81b2a90365cfa476cab8611edf1586404a88": {
            "Name": "postgres",
            "EndpointID": "069411d5c42b3b968ce38b92b7122c608f1dca696517122728f23086fdce53c7",
            "MacAddress": "02:42:ac:11:00:03",
            "IPv4Address": "172.17.0.3/16",
            "IPv6Address": ""
        }
    },
    "Options": {
        "com.docker.network.bridge.default_bridge": "true",
        "com.docker.network.bridge.enable_icc": "true",
        "com.docker.network.bridge.enable_ip_masquerade": "true",
        "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
        "com.docker.network.bridge.name": "docker0",
        "com.docker.network.driver.mtu": "1500"
    },
    "Labels": {}
}

似乎主机名 postgres应该解析为 ip的 172.17.0.3。

当我在python中执行此操作时，它会起作用:

import psycopg2
conn = psycopg2.connect(host="172.17.0.3", port = 5432, database="hi", user="postgres", password="")

如何使用其名称作为主机连接到名为 postgres的容器？

Answer 1

您正确地怀疑这是一个 docker 网络问题。

如您所见，名称解析不适用于所使用的默认网络。为了使名称解析有效，您需要使用一个单独的网络，如下所示:

docker network create my-network

然后，使用 --net参数运行容器:

docker run -d --rm --name postgres --publish 5432:5432 -e POSTGRES_HOST_AUTH_METHOD=trust -e POSTGRES_DB=hi --net my-network postgres:9.6
docker run -d --rm --name redis --publish 6379:6379 --net my-network redis
docker run -d --rm --name web --publish 8000:8000 --net my-network python:3.6.8-stretch sleep 1000

然后，使用此用户创建的网络将允许您使用容器名称:

>>> import psycopg2
>>> conn = psycopg2.connect(host="postgres", port = 5432, database="hi", user="postgres", password="")
>>> conn.info.user
'postgres'

请注意，对于使用多个容器的设置，我建议您使用 docker-compose而不是 docker命令，因为该网络是在后台为您设置的。