1、报错提示
将网络配置信息写入了ETCD中，启动flanneld测试时一直报错，具体报错如下：
[root@master1 ~]# tail -100f /var/log/messages
Dec 15 23:39:22 localhost flanneld: E1215 23:39:22.688405 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:23 localhost flanneld: timed out
Dec 15 23:39:23 localhost flanneld: E1215 23:39:23.701707 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:24 localhost flanneld: timed out
Dec 15 23:39:24 localhost flanneld: E1215 23:39:24.717330 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:25 localhost flanneld: timed out
Dec 15 23:39:25 localhost flanneld: E1215 23:39:25.725860 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:26 localhost flanneld: timed out
Dec 15 23:39:26 localhost flanneld: E1215 23:39:26.733186 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:27 localhost flanneld: timed out
Dec 15 23:39:27 localhost flanneld: E1215 23:39:27.744882 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:28 localhost flanneld: timed out
Dec 15 23:39:28 localhost flanneld: E1215 23:39:28.755176 31176 main.go:382] Couldn't fetch network config: 100: Key not found (/coreos.com) [10]
Dec 15 23:39:29 localhost systemd: flanneld.service start operation timed out. Terminating.
Dec 15 23:39:29 localhost flanneld: I1215 23:39:29.528718 31176 main.go:370] shutdownHandler sent cancel signal...
Dec 15 23:39:29 localhost systemd: Failed to start Flanneld overlay address etcd agent.
Dec 15 23:39:29 localhost systemd: Unit flanneld.service entered failed state.
Dec 15 23:39:29 localhost systemd: flanneld.service failed.
Dec 15 23:39:29 localhost systemd: flanneld.service holdoff time over, scheduling restart.
Dec 15 23:39:29 localhost systemd: Stopped Flanneld overlay address etcd agent.
Dec 15 23:39:29 localhost systemd: Starting Flanneld overlay address etcd agent...
Dec 15 23:39:29 localhost flanneld: warning: ignoring ServerName for user-provided CA for backwards compatibility is deprecated
Dec 15 23:39:29 localhost flanneld: I1215 23:39:29.975581 31202 main.go:514] Determining IP address of default interface
Dec 15 23:39:29 localhost flanneld: I1215 23:39:29.976573 31202 main.go:527] Using interface with name ens33 and address 192.168.31.101
Dec 15 23:39:29 localhost flanneld: I1215 23:39:29.976606 31202 main.go:544] Defaulting external address to interface address (192.168.31.101)
Dec 15 23:39:29 localhost flanneld: I1215 23:39:29.983495 31202 main.go:244] Created subnet manager: Etcd Local Manager with Previous Subnet: None
Dec 15 23:39:29 localhost flanneld: I1215 23:39:29.983525 31202 main.go:247] Installing signal handlers
2、配置过程
（1）配置Falnnel使用的子网信息并存储到etcd
[root@master1 ~]# /opt/etcd/bin/etcdctl --cacert=/opt/etcd/ssl/ca.pem --cert=/opt/etcd/ssl/server.pem --key=/opt/etcd/ssl/server-key.pem --endpoints="https://192.
168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379" put /coreos.com/network/config '{ "Network": "172.17.0.0/16", "Backend": {"Type": "vxlan"}}'
OK
（2）获取配置的子网信息
[root@master1 ~]# /opt/etcd/bin/etcdctl --cacert=/opt/etcd/ssl/ca.pem --cert=/opt/etcd/ssl/server.pem --key=/opt/etcd/ssl/server-key.pem --endpoints="https://192.
168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379" get /coreos.com/network/config
/coreos.com/network/config
{ "Network": "172.17.0.0/16", "Backend": {"Type": "vxlan"}}
（3）配置flanneld信息
[root@master1 ~]# vim /opt/kubernetes/cfg/flanneld
FLANNEL_OPTIONS="--etcd-endpoints=https://192.168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379 -etcd-cafile=/opt/etcd/ssl/ca.pem -etcd-certfile=/opt/etcd/ssl/server.pem -etcd-keyfile=/opt/etcd/ssl/server-key.pem"
（4）systemd管理Flannel：
[root@master1 ~]# vim /usr/lib/systemd/system/flanneld.service
[Unit]
Description=Flanneld overlay address etcd agent
After=network-online.target network.target
Before=docker.service
[Service]
Type=notify
EnvironmentFile=/opt/kubernetes/cfg/flanneld
ExecStart=/opt/kubernetes/bin/flanneld --ip-masq $FLANNEL_OPTIONS
ExecStartPost=/opt/kubernetes/bin/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/subnet.env
Restart=on-failure
[Install]
WantedBy=multi-user.target
（5）启动flanneld服务
[root@master1 ~]# iptables -I INPUT -s 192.168.0.0/24 -j ACCEPT
[root@master1 ~]# iptables -I INPUT -s 172.17.0.0/24 -j ACCEPT
[root@master1 ~]# systemctl daemon-reload
[root@master1 ~]# systemctl start flanneld
[root@master1 ~]# systemctl enable flanneld
提示开篇所示的错误！！
3、问题原因
github上与此问题相关的一些issues，也即flanneld目前不能与etcdV3直接交互
https://github.com/coreos/flannel/issues/554
https://github.com/coreos/flannel/issues/755
4、解决办法
按如下方法调整后，flanneld服务正常启动。
（1） 开启etcd 支持V2api功能，在etcd启动参数中加入 --enable-v2参数，并重启etcd2
[root@master1 ~]# vim /usr/lib/systemd/system/etcd.service
[Unit]
Description=Etcd Server
After=network.target
After=network-online.target
Wants=network-online.target
[Service]
Type=notify
EnvironmentFile=/opt/etcd/cfg/etcd.conf
ExecStart=/opt/etcd/bin/etcd --cert-file=/opt/etcd/ssl/server.pem \
--key-file=/opt/etcd/ssl/server-key.pem \
--peer-cert-file=/opt/etcd/ssl/server.pem \
--peer-key-file=/opt/etcd/ssl/server-key.pem \
--trusted-ca-file=/opt/etcd/ssl/ca.pem \
--peer-trusted-ca-file=/opt/etcd/ssl/ca.pem \
--logger=zap \
--enable-v2
Restart=on-failure
LimitNOFILE=65536
[Install]
WantedBy=multi-user.target
[root@master1 ~]# systemctl daemon-reload
[root@master1 ~]# systemctl restart etcd
[root@master1 ~]# ETCDCTL_API=2 /opt/etcd/bin/etcdctl --ca-file=/opt/etcd/ssl/ca.pem --cert-file=/opt/etcd/ssl/server.pem --key-file=/opt/etcd/ssl/server-key.pem
--endpoints="https://192.168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379" cluster-health
member 969af216adf1108 is healthy: got healthy result from https://192.168.31.102:2379
member 4d384076f6bc6dde is healthy: got healthy result from https://192.168.31.101:2379
member ea776d7c1c3c494c is healthy: got healthy result from https://192.168.31.103:2379
cluster is healthy
（2）删除原来写入的子网信息
/opt/etcd/bin/etcdctl --cacert=/opt/etcd/ssl/ca.pem --cert=/opt/etcd/ssl/server.pem --key=/opt/etcd/ssl/server-key.pem --endpoints="https://192.
168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379" del /coreos.com/network/config
（3）重新使用V2写入子网信息
[root@master1 ~]# ETCDCTL_API=2 /opt/etcd/bin/etcdctl --ca-file=/opt/etcd/ssl/ca.pem --cert-file=/opt/etcd/ssl/server.pem --key-file=/opt/etcd/ssl/server-key.pem
--endpoints="https://192.168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379" set /coreos.com/network/config '{ "Network": "172.17.0.0/16", "Backend": {"Type": "vxlan"}}
'{ "Network": "172.17.0.0/16", "Backend": {"Type": "vxlan"}}
[root@master1 ~]# ETCDCTL_API=2 /opt/etcd/bin/etcdctl --ca-file=/opt/etcd/ssl/ca.pem --cert-file=/opt/etcd/ssl/server.pem --key-file=/opt/etcd/ssl/server-key.pem
--endpoints="https://192.168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379" get /coreos.com/network/config
{ "Network": "172.17.0.0/16", "Backend": {"Type": "vxlan"}}
（4）重启flanneld服务
[root@master1 ~]# iptables -I INPUT -s 192.168.0.0/24 -j ACCEPT
[root@master1 ~]# iptables -I INPUT -s 172.17.0.0/24 -j ACCEPT
[root@master1 ~]# systemctl daemon-reload
[root@master1 ~]# systemctl start flanneld
[root@master1 ~]# systemctl enable flanneld
[root@master1 ~]# systemctl status flanneld
● flanneld.service - Flanneld overlay address etcd agent
Loaded: loaded (/usr/lib/systemd/system/flanneld.service; enabled; vendor preset: disabled)
Active: active (running) since Tue 2020-12-15 23:40:07 CST; 4min 15s ago
Main PID: 31202 (flanneld)
CGroup: /system.slice/flanneld.service
└─31202 /opt/kubernetes/bin/flanneld --ip-masq --etcd-endpoints=https://192.168.31.101:2379,https://192.168.31.102:2379,https://192.168.31.103:2379 ...
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.171127 31202 iptables.go:155] Adding iptables rule: -s 172.17.0.0/16 -j ACCEPT
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.180271 31202 iptables.go:167] Deleting iptables rule: -s 172.17.0.0/16 ! -d 224.0.0.0/4 -j MASQUERADE
Dec 15 23:40:07 master1 systemd[1]: Started Flanneld overlay address etcd agent.
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.182977 31202 iptables.go:167] Deleting iptables rule: ! -s 172.17.0.0/16 -d 172.17.51.0/24 -j RETURN
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.189015 31202 iptables.go:155] Adding iptables rule: -d 172.17.0.0/16 -j ACCEPT
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.195921 31202 iptables.go:167] Deleting iptables rule: ! -s 172.17.0.0/16 -d 172.17.0.0/16 -j MASQUERADE
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.203488 31202 iptables.go:155] Adding iptables rule: -s 172.17.0.0/16 -d 172.17.0.0/16 -j RETURN
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.212158 31202 iptables.go:155] Adding iptables rule: -s 172.17.0.0/16 ! -d 224.0.0.0/4 -j MASQUERADE
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.219014 31202 iptables.go:155] Adding iptables rule: ! -s 172.17.0.0/16 -d 172.17.51.0/24 -j RETURN
Dec 15 23:40:07 master1 flanneld[31202]: I1215 23:40:07.228946 31202 iptables.go:155] Adding iptables rule: ! -s 172.17.0.0/16 -d 172.17.0.0/16 -j MASQUERADE
（5）查看各节点IP，并ping另一节点的docker0网络，以及确认docker0与flannel.1在同一网段
[root@master1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:14:36:9d brd ff:ff:ff:ff:ff:ff
inet 192.168.31.101/24 brd 192.168.31.255 scope global noprefixroute ens33
valid_lft forever preferred_lft forever
inet6 fe80::eddd:ed6f:516a:ac4/64 scope link noprefixroute
valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:05:2c:ef:6c brd ff:ff:ff:ff:ff:ff
inet 172.17.51.1/24 brd 172.17.51.255 scope global docker0
valid_lft forever preferred_lft forever
4: flannel.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UNKNOWN group default
link/ether 02:fb:8d:80:3f:b2 brd ff:ff:ff:ff:ff:ff
inet 172.17.51.0/32 scope global flannel.1
valid_lft forever preferred_lft forever
inet6 fe80::fb:8dff:fe80:3fb2/64 scope link
valid_lft forever preferred_lft forever
[root@master1 ~]# ping 172.17.29.1
PING 172.17.29.1 (172.17.29.1) 56(84) bytes of data.
64 bytes from 172.17.29.1: icmp_seq=1 ttl=64 time=10.1 ms
64 bytes from 172.17.29.1: icmp_seq=2 ttl=64 time=0.635 ms
