初识DOCKER(14)–Flannel制备Docker跨主机网络

借助Flannel,可以使得docker实例具备跨宿主机的网络通讯能力,并能使容器在Flannel内网的IP地址固定。

在每台主机上准备Go编译平台以及编译etcd和flannel

#wget https://storage.googleapis.com/golang/go1.6.2.linux-amd64.tar.gz
--2016-06-22 14:53:31--  https://storage.googleapis.com/golang/go1.6.2.linux-amd64.tar.gz
Resolving storage.googleapis.com (storage.googleapis.com)... 74.125.23.128, 2404:6800:4005:80a::2010
Connecting to storage.googleapis.com (storage.googleapis.com)|74.125.23.128|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 84840658 (81M) [application/x-gzip]
Saving to: go1.6.2.linux-amd64.tar.gz100%[===============================================================>] 84,840,658   429KB/s   in 2m 46s2016-06-22 14:56:18 (499 KB/s) - go1.6.2.linux-amd64.tar.gz saved [84840658/84840658]
#tar -zxvf go1.6.2.linux-amd64.tar.gz && cd go
#export GOBIN=`pwd`/bin
#export PATH=$GOROOT/bin:$PATH
#export GOOS=linux
#export GOARCH=amd64
#cd ..
#git clone https://github.com/coreos/etcd.git
Cloning into 'etcd'...                                                                          blog.nvacg.org版权所有
remote: Counting objects: 48104, done.
remote: Compressing objects: 100% (18/18), done.
remote: Total 48104 (delta 2), reused 0 (delta 0), pack-reused 48084
Receiving objects: 100% (48104/48104), 25.42 MiB | 1.29 MiB/s, done.
Resolving deltas: 100% (30114/30114), done.
Checking connectivity... done.

 

#git clone https://github.com/coreos/flannel.git
Cloning into 'flannel'...
remote: Counting objects: 5686, done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 5686 (delta 0), reused 0 (delta 0), pack-reused 5682
Receiving objects: 100% (5686/5686), 10.95 MiB | 1.40 MiB/s, done.
Resolving deltas: 100% (1930/1930), done.
Checking connectivity... done.
#cd etcd && ./build && cd ..
./build
#cd flannel && ./build && cd ..
Building flanneld...                                                      blog.nvacg.org版权所有

随即可以在etcd/bin和flannel/bin目录中找到二进制执行文件,将他们拷贝到系统执行目录下

#ls etcd/bin && ls flannel/bin
etcd  etcdctl
flannel
#cp -a etcd/bin/. /usr/sbin
#cp -a flannel/bin/. /usr/sbin
#cp flannel/dist/mk-docker-opts.sh /usr/sbin            blog.nvacg.org版权所有

在主机1上启动etcd,宿主机1的实IP是172.16.71.33,参数中各端口可随意指定,为防止混淆,所有宿主机均使用同样的端口供etcd监听,当后续启动时需要将 --initial-cluster-state new 改为 --initial-cluster-state existing

#etcd --name node1 --initial-advertise-peer-urls http://172.16.71.33:9030 --listen-peer-urls http://172.16.71.33:9030 --advertise-client-urls http://172.16.71.33:9020 --listen-client-urls http://0.0.0.0:9020 --initial-cluster-token nvacg-docker-cluster-webserver --initial-cluster node1=http://172.16.71.33:9030,node2=http://172.16.71.34:9030 --initial-cluster-state new > /dev/null 2>&1 &

在主机2上启动etcd,宿主机2的实IP是172.16.71.34 ,当后续启动时需要将 --initial-cluster-state new 改为 --initial-cluster-state existing

#etcd --name node2 --initial-advertise-peer-urls http://172.16.71.34:9030 --listen-peer-urls http://172.16.71.34:9030 --advertise-client-urls http://172.16.71.34:9020 --listen-client-urls http://0.0.0.0:9020 --initial-cluster-token nvacg-docker-cluster-webserver --initial-cluster node1=http://172.16.71.33:9030,node2=http://172.16.71.34:9030 --initial-cluster-state new > /dev/null 2>&1 &

接下来设置内部网段,在任意节点上执行 (当etcd的启动参数使用默认端口2379时,可不加 —endpoints 参数),子网掩码至少是/16

#etcdctl --endpoints 127.0.0.1:9020 set /coreos.com/network/config '{"Network":"10.128.0.0/16"}'

查看下节点的存活情况

#etcdctl --endpoints 127.0.0.1:9020 cluster-health
member 8113781b1480a5bd is healthy: got healthy result from http://172.16.71.33:9020
member b61040edf801d4e9 is healthy: got healthy result from http://172.16.71.34:9020
cluster is healthy                                                       blog.nvacg.org版权所有

在主机1上启动flanneld服务

#flanneld -etcd-endpoints http://127.0.0.1:9020 > /dev/null 2>&1 &
[2] 2393
I0624 11:09:16.273288 02393 main.go:126] Installing signal handlers
I0624 11:09:16.273572 02393 manager.go:133] Determining IP address of default interface
I0624 11:09:16.273987 02393 manager.go:163] Using 172.16.71.33 as external interface
I0624 11:09:16.274054 02393 manager.go:164] Using 172.16.71.33 as external endpoint
I0624 11:09:16.276052 02393 local_manager.go:150] Found lease (192.168.30.128/25) for current IP (172.16.71.33) but not compatible with current config, deleting
I0624 11:09:16.281494 02393 local_manager.go:179] Picking subnet in range 10.128.1.0 ... 10.128.255.0
I0624 11:09:16.284777 02393 manager.go:246] Lease acquired: 10.128.12.0/24
I0624 11:09:16.284939 02393 network.go:98] Watching for new subnet leases
I0624 11:09:39.700273 02393 network.go:191] Subnet added: 10.128.51.0/24

在主机2上启动flanneld服务

#flanneld -etcd-endpoints http://127.0.0.1:9020 > /dev/null 2>&1 &
[2] 9840
root@dockertest:/home/smm/flannel/dist# I0624 11:09:42.665807 09840 main.go:126] Installing signal handlers
I0624 11:09:42.666043 09840 manager.go:133] Determining IP address of default interface
I0624 11:09:42.666483 09840 manager.go:163] Using 172.16.71.34 as external interface
I0624 11:09:42.666521 09840 manager.go:164] Using 172.16.71.34 as external endpoint
I0624 11:09:42.668116 09840 local_manager.go:179] Picking subnet in range 10.128.1.0 ... 10.128.255.0
I0624 11:09:42.697901 09840 manager.go:246] Lease acquired: 10.128.51.0/24
I0624 11:09:42.698173 09840 network.go:98] Watching for new subnet leases
I0624 11:09:42.699231 09840 network.go:191] Subnet added: 10.128.12.0/24

重新配置docker网卡,在各节点上执行

#mk-docker-opts.sh -i
#. /run/flannel/subnet.env
#ifconfig docker0 $FLANNEL_SUBNET
#service docker restart                                                     blog.nvacg.org版权所有

如果做了上述更改后,实例无法连接到外网,可以先停止docker服务,然后执行
iptables -t nat -F
然后重新启动docker服务即可

然后直接将参数写入到docker的环境变量/etc/default/docker中去,这需要我们对/run/flannel/subnet.env进行一下翻译:

--bip = $FLANNEL_SUBNET
--ip-masq = $FLANNEL_IPMASQ
--mtu = $FLANNEL_MTU

这样当docker启动(或重新启动)的时侯会自动将docker0网桥的设置改为flannel相同的设置,建议是直接重启一下宿主机,如果直接重启docker,可能服务会无法启动,这是因为先前系统中已经存在docker0网桥,并处于活动状态,docker尝试更改它的参数但是失败了。此时需要手动停止网桥,删除它,再启动(或重启)docker服务应该就可以了。

以主机1为例,此时该主机上docker0网卡和flannel0网卡的状态如下

#ifconfig
docker0   Link encap:Ethernet  HWaddr 7e:41:01:f7:2f:bc
inet addr:10.128.12.1  Bcast:10.128.12.255  Mask:255.255.255.0
inet6 addr: fe80::7c41:1ff:fef7:2fbc/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:107 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B)  TX bytes:16271 (16.2 KB)
 
eth0      Link encap:Ethernet  HWaddr 00:0c:29:22:0c:3a
inet addr:172.16.71.33  Bcast:172.16.71.255  Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe22:c3a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:117369 errors:0 dropped:0 overruns:0 frame:0
TX packets:101022 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:11207503 (11.2 MB)  TX bytes:9848109 (9.8 MB)
 
flannel0  Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:10.128.12.0  P-t-P:10.128.12.0  Mask:255.255.0.0
UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1472  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)                       blog.nvacg.org版权所有

看下flannel节点信息

#etcdctl --endpoints 127.0.0.1:9020 ls /coreos.com/network/subnets
/coreos.com/network/subnets/10.128.12.0-24
/coreos.com/network/subnets/10.128.51.0-24            blog.nvacg.org版权所有

现在,主机1上承载的实例可以ping到主机2上承载的实例,也可以连通主机2上承载的实例中监听的端口。

目前,flannel方式组网仍然是由docker来分配地址,即使解决了跨主机联网的问题,各实例分配到的地址仍然是动态的,仅供测试使用,若需要在无人值守环境使用,需要配合skydns使用,通过主机名方式解析其他实例的地址。对于需要设置固定IP的场合,可以先启动容器或镜像后经由pipework分配静态IP的方式。对于上例中宿主机1上docker的网络是10.128.12.0/24,则其网关默认分配为10.128.12.1,则pipework参数为

pipework docker0 容器名称或容器ID 10.128.12.XXX/24@10.128.12.1

另外需要声明一点,由于采用flannel时,对外映射端口(不是指实例到实例,而是指对外提供的服务)的方式仍然是通过iptables曝光端口到宿主机后由宿主机对外提供该端口的方式,因此启动容器时仍然采用-p参数来映射端口,由于需要使用该参数来映射端口,故不能指定--net=none参数,否则端口映射无效。实际经过测试,即使是常规方式启动的实例仍然可以使用pipework来为实例设置第二IP。

如果你是采用--net=none参数启动+pipework设置网络参数的,若要暴露端口,请直接修改iptables来达到暴露端口的目的。

 


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