11. 第十篇 网络组件flanneld安装及使用

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kubernetes需要使用第三方的网络插件来实现kubernetes的网络功能，这样一来，安装网络插件成为必要前提；第三方网络插件有多种，常用的有flanneld、calico和cannel（flanneld+calico），不同的网络组件，都提供基本的网络功能，为各个Node节点提供IP网络等。

二进制下载链接https://github.com/coreos/flannel/releases/download/v0.11.0/flannel-v0.11.0-linux-amd64.tar.gz，下载完成后，分发到所有节点的/data/k8s/bin/目录下。

Flannel插件支持三种通信模式如下

Flanneld配置写到Etcd中

cd /data/k8s/work
source /data/k8s/bin/env.sh
etcdctl \
  --endpoints=${ETCD_ENDPOINTS} \
  --ca-file=/data/k8s/work/ca.pem \
  --cert-file=/data/k8s/work/flanneld.pem \
  --key-file=/data/k8s/work/flanneld-key.pem \
  mk ${FLANNEL_ETCD_PREFIX}/config '{"Network":"'${CLUSTER_CIDR}'", "SubnetLen": 21, "Backend": {"Type": "vxlan", "DirectRouting": true}}'

这里我们使用VxLan+DirectRouting的模式进行通信，Node节点网段相同，直接路由，节点网段不同，使用Vxlan进行封装；

查看etcd中存储配置

#!/bin/bash

source /data/k8s/bin/env.sh

etcdctl \
  --endpoints=${ETCD_ENDPOINTS} \
  --ca-file=/etc/kubernetes/cert/ca.pem \
  --cert-file=/etc/flanneld/cert/flanneld.pem \
  --key-file=/etc/flanneld/cert/flanneld-key.pem \
  get ${FLANNEL_ETCD_PREFIX}/config

结果如下：
{"Network":"172.19.0.0/16", "SubnetLen": 21, "Backend": {"Type": "vxlan", "DirectRouting": true}}

创建Flanneld启动文件并分发

#!/bin/bash

cd /data/k8s/work
source /data/k8s/bin/env.sh

cat > flanneld.service << EOF
[Unit]
Description=Flanneld overlay address etcd agent
After=network.target
After=network-online.target
Wants=network-online.target
After=etcd.service
Before=docker.service
[Service]
Type=notify
ExecStart=/data/k8s/bin/flanneld \\
  -etcd-cafile=/etc/kubernetes/cert/ca.pem \\
  -etcd-certfile=/etc/flanneld/cert/flanneld.pem \\
  -etcd-keyfile=/etc/flanneld/cert/flanneld-key.pem \\
  -etcd-endpoints=${ETCD_ENDPOINTS} \\
  -etcd-prefix=${FLANNEL_ETCD_PREFIX} \\
  -iface=${IFACE} \\
  -ip-masq
ExecStartPost=/data/k8s/bin/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker
Restart=always
RestartSec=5
StartLimitInterval=0
[Install]
WantedBy=multi-user.target
RequiredBy=docker.service
EOF

for node_ip in ${NODE_IPS[@]}
do
    echo ">>> ${node_ip}"
    scp flannel

配置详解

启动flannel

#!/bin/bash

cd /data/k8s/work
source /data/k8s/bin/env.sh

for node_ip in ${NODE_IPS[@]}
do
    echo ">>> ${node_ip}"
    ssh root@${node_ip} "systemctl daemon-reload && systemctl enable flanneld && systemctl restart flanneld"
done

验证

#!/bin/bash
source /data/k8s/bin/env.sh
for node_ip in ${NODE_IPS[@]}
do
    echo ">>> ${node_ip}"
    ssh root@${node_ip} "systemctl status flanneld|grep -i Active"
done

验证结果

>>> 192.168.16.104
   Active: active (running) since Sun 2019-12-29 18:03:43 CST; 1 months 0 days ago
>>> 192.168.16.105
   Active: active (running) since Sat 2019-12-28 22:33:27 CST; 1 months 1 days ago
>>> 192.168.16.106
   Active: active (running) since Sat 2019-12-28 22:33:27 CST; 1 months 1 days ago
>>> 192.168.16.107
   Active: active (running) since Sat 2019-12-28 22:33:28 CST; 1 months 1 days ago

查看已分配的网段信息

#!/bin/bash

source /data/k8s/bin/env.sh

etcdctl \
  --endpoints=${ETCD_ENDPOINTS} \
  --ca-file=/etc/kubernetes/cert/ca.pem \
  --cert-file=/etc/flanneld/cert/flanneld.pem \
  --key-file=/etc/flanneld/cert/flanneld-key.pem \
  ls ${FLANNEL_ETCD_PREFIX}/subnets

结果如下：
/kubernetes/network/subnets/172.19.120.0-21
/kubernetes/network/subnets/172.19.184.0-21
/kubernetes/network/subnets/172.19.72.0-21
/kubernetes/network/subnets/172.19.56.0-21

查看下分配网段的详情：

#!/bin/bash

source /data/k8s/bin/env.sh

etcdctl \
  --endpoints=${ETCD_ENDPOINTS} \
  --ca-file=/etc/kubernetes/cert/ca.pem \
  --cert-file=/etc/flanneld/cert/flanneld.pem \
  --key-file=/etc/flanneld/cert/flanneld-key.pem \
  get ${FLANNEL_ETCD_PREFIX}/subnets/172.19.120.0-21

结果如下：
{"PublicIP":"192.168.16.104","BackendType":"vxlan","BackendData":{"VtepMAC":"aa:ea:b2:e1:88:a5"}}

总结

网络插件有多种，根据公司或个人实际情况进行选择，网上很多前辈说flannel支持的网络规模受限，建议使用calico，由于测试环境规模不大，这里使用flannel即可满足。