docker容器网络 - 同一个host下的容器间通讯

时间 2019-11-07

原文原文链接

对于复杂的应用，不可避免须要多个服务部署在多个容器中，而且服务间存在相互间通讯的状况。好比服务A须要链接mysql的容器。本文将介绍docker的容器网络，并经过实践解决在同一个docker Host主机下的容器间通讯的问题。node

在安装好docker后，docker将建立一个linux网桥docker0，它在内核层连通了其余的物理或虚拟网卡，也就是全部容器和本地主机都放到同一个物理网络。咱们能够经过 brctl 命令查看网桥的信息，brctl是须要自行安装的。mysql

[root@localhost ~]# brctl show
bridge name	bridge id		STP enabled	interfaces
br-1a83283cbf04		8000.0242123432ad	no		
br-70590112bbda		8000.0242927ea6d9	no		
docker0		8000.024232ccc082	no

另外，docker还会给咱们建立三个网络：bridge/host/none。咱们能够经过network ls命令查看当前宿主机中全部的docker网络。linux

[root@localhost ~]# docker network ls

NETWORK ID          NAME                DRIVER              SCOPE
5a9ac72df73f        bridge              bridge              local
7d9eb4bd321c        host                host                local
4b740dab2aab        none                null                local

其中，网桥bridge模式是在实际项目中经常使用的。接下来，以交互模式启动两个busybox容器。在没有指定相关网络的状况下，容器都会链接到默认的bridge网络。咱们能够经过 --network 参数指定容器链接的网络。sql

[root@localhost ~]# docker run -itd --name=busybox1 busybox
2813aba53acd688fa69807158830bef27b4ea8dc2ecfe13e7e357ce98a204f0b

[root@localhost ~]# docker run -itd --name=busybox2 busybox
83fbeeb4e0527ece0602729415a57383b474284143a381e0a27561a69d75b1f5

启动容器后，检查当前默认bridge网络状况。busybox1和busybox2容器已经链接到了bridge网络，除此以外，还能够获取到两个容器的IP地址。docker

[root@localhost ~]# docker network inspect bridge


[
    {
        "Name": "bridge",
        "Id": "5a9ac72df73f19beaade92a28d705509fd24c350497dd90ecae224fdb18214bc",
        "Created": "2018-12-25T16:30:26.58008782+08:00",
        "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": {
            "2813aba53acd688fa69807158830bef27b4ea8dc2ecfe13e7e357ce98a204f0b": {
                "Name": "busybox1",
                "EndpointID": "522f2b4b072098525939cc6b313f5673f82444d8ef6807bac0efcdce6a7c8418",
                "MacAddress": "02:42:ac:11:00:02",
                "IPv4Address": "172.17.0.2/16",
                "IPv6Address": ""
            },
            "83fbeeb4e0527ece0602729415a57383b474284143a381e0a27561a69d75b1f5": {
                "Name": "busybox2",
                "EndpointID": "e277940484662a341730766300149c2f63974d0b9e9cbd6c531bc7c8c37f31f9",
                "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": {}
    }
]

接下来，咱们测试下两个容器的互通状况。bash

进入busybox1容器，分别ping 容器busybox2的IP和容器名，能够发现能够经过IP地址ping通busybox2，可是不能经过容器ping通。其中，172.17.0.3是busybox2的IP地址。服务器

[root@localhost ~]# docker attach  2813aba53acd

/ # ping  172.17.0.3
PING 172.17.0.3 (172.17.0.3): 56 data bytes
64 bytes from 172.17.0.3: seq=0 ttl=64 time=0.090 ms
64 bytes from 172.17.0.3: seq=1 ttl=64 time=0.193 ms


/ # ping busybox2

在容器中，能够查看容器的hosts文件，里面没有任何关于busybox2容器的信息。网络

/ # 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
172.17.0.2	2813aba53acd

在计算机网络中，想经过域名ping通其它网站，有两种方法：一种是本地的hosts文件，里面配置的是路由规则；另外一种是DNS服务，经过DNS服务器返回正确的IP地址。那么docker是否也能够经过容器名访问其它容器的方式呢？oop

（1）link链接测试

默认的桥接网络支持使用端口映射和 docker run --link 命令，实现容器间互相通讯。该方法已经在官方文档中标识为不推荐使用。

https://docs.docker.com/network/links/

下面，继续介绍经过 --link 参数时间容器间通讯。咱们将建立busybox3和busybox4两个容器，其中busybox4能够经过busybox3容器名与busybox3容器进行通讯。

新建busybox3和busybox4，其中busybox4经过 --link 参数指定链接到 busybox3容器。

[root@localhost ~]# docker run -itd --name=busybox3 busybox
a539a74a9ecad6782f88944604bbdd045f4a1fd6965a3484e04d1dbbec1e511d

[root@localhost ~]# docker run -itd --link busybox3  --name=busybox4 busybox
f6c470354b55300106a3a8960c4c935dcdd0cb0f7ad6c941c8f040fdb0cd0a04

从新进入容器busybox4，查看hosts文件，能够看到host文件中已经出现busybox3容器，并配置了路由规则。

/ # 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
172.17.0.4	busybox3 a539a74a9eca
172.17.0.5	f6c470354b55

测试busybox4链接容器busybox3

/ # ping busybox3
PING busybox3 (172.17.0.4): 56 data bytes
64 bytes from 172.17.0.4: seq=0 ttl=64 time=0.077 ms
64 bytes from 172.17.0.4: seq=1 ttl=64 time=0.125 ms
^C
--- busybox3 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss

（2）自定义bridge网络，实现容器间通讯

从 Docker 1.10 版本开始，docker daemon 实现了一个内嵌的 DNS server，使容器能够直接经过“容器名”通讯。使用默认的bridge网络，不能经过DNS server实现经过容器名通讯，可是使用自定义bridge网络能够作到经过容器名互相通讯。

经过 docker network create 命令建立一个自定义的bridge网络

[root@localhost ~]# docker network create --driver bridge busybox_bridge
1a83283cbf047fea14231daef7edb67e8a11383f61c176e5c4983e961e757a1e

[root@localhost ~]# docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
53c7e86fc3ec        bridge              bridge              local
1a83283cbf04        busybox_bridge      bridge              local
7d9eb4bd321c        host                host                local
4b740dab2aab        none                null                local

分别建立busybox5/busybox6容器，在run命令里加入--network参数使两个容器绑定到前面自定义的网络中。

[root@localhost ~]# docker run -itd --network busybox_bridge --name busybox5 busybox
ccd81a357cf48af2c01c64cd1ef7a4c463b415bd477d965f19a3b47be3760208

[root@localhost ~]# docker run -itd --network busybox_bridge --name busybox6 busybox
d3e5af0eeb86a480fe868bb9ea7cea2cb29b7f12b7f680cbd5b48288c15b10e9

查看busybox_bridge网络状况，能够看到，busybox5/busybox6容器已经绑定到该网络中。

[root@localhost ~]# docker network inspect busybox_bridge

[
    {
        "Name": "busybox_bridge",
        "Id": "1a83283cbf047fea14231daef7edb67e8a11383f61c176e5c4983e961e757a1e",
        "Created": "2018-12-25T22:17:10.981291803+08:00",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "ccd81a357cf48af2c01c64cd1ef7a4c463b415bd477d965f19a3b47be3760208": {
                "Name": "busybox5",
                "EndpointID": "4da57d779c14bdee415eee69a92dd802250bf6e89cd744f8543c4498e32aebdc",
                "MacAddress": "02:42:ac:12:00:02",
                "IPv4Address": "172.18.0.2/16",
                "IPv6Address": ""
            },
            "d3e5af0eeb86a480fe868bb9ea7cea2cb29b7f12b7f680cbd5b48288c15b10e9": {
                "Name": "busybox6",
                "EndpointID": "6f130cc2055399c051cd556e20835793332605f9ee636885c602f2b257f9db80",
                "MacAddress": "02:42:ac:12:00:03",
                "IPv4Address": "172.18.0.3/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

接下来进入busybox5容器，测试是否能够经过容器名ping通busybox6

[root@localhost ~]# docker attach busybox5


/ # ping busybox6
PING busybox6 (172.18.0.3): 56 data bytes
64 bytes from 172.18.0.3: seq=0 ttl=64 time=0.107 ms
64 bytes from 172.18.0.3: seq=1 ttl=64 time=0.149 ms

看下容器的hosts文件，文件里是没有busybox6的映射配置的。那么它是怎么经过容器名访问到另外一个容器的呢？答案就是内嵌的dns服务器。

/ # 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
172.18.0.2	ccd81a357cf4

查看DNS服务，能够看到指定了DNS解析服务地址：nameserver 127.0.0.11 。若是是链接到默认bridge网络的容器，在resolv.conf文件是没有127.0.0.11这个DNS服务器配置的

/ # cat /etc/resolv.conf 
nameserver 127.0.0.11
options ndots:0

容器中的DNS名称解析优先级顺序为：

内置DNS服务器127.0.0.11。
经过--dns等参数为容器配置的DNS服务器。
docker守护进程的--dns服务配置（默认为8.8.8.8和8.8.4.4）
宿主机上的DNS设置。

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