通过Consul集群的failover测试，我们可以了解到它的高可用工作机制。
consul节点IP角色consul版本日志路径consul01192.168.101.11server0.9.3/var/log/consulconsul02192.168.101.12server0.9.3/var/log/consulconsul03192.168.101.13server(leader)0.9.3/var/log/consul
注：我们是验证consul cluster的高可用性，而非验证consul自带的Geo failover(注册服务的故障转移功能)。
当前集群初始状态(client节点忽略)
[root@consul01 consul]# ./consul operator raft list-peersNode ID Address State Voter RaftProtocolconsul02 192.168.101.12:8300 192.168.101.12:8300 follower true 2consul03 192.168.101.13:8300 192.168.101.13:8300 leader true 2consul01 192.168.101.11:8300 192.168.101.11:8300 follower true 2[root@consul01 consul]# ./consul membersNode Address Status Type Build Protocol DC Segmentconsul01 192.168.101.11:8301 alive server 0.9.3 2 dc consul02 192.168.101.12:8301 alive server 0.9.3 2 dc consul03 192.168.101.13:8301 alive server 0.9.3 2 dc ...TSOP域的consul为3个server节点集群，理论上支持最多一个server节点故障，因此我们测试一个server节点故障是否影响集群
consul cluster 模拟故障测试
§1. 停掉一个follower server节点
此处以consul01节点为例
[root@consul01 consul]# systemctl stop consul其它节点日志信息
[root@consul02 ~]# tail -100 /var/log/consul 2019/02/12 02:30:38 [INFO] serf: EventMemberFailed: consul01.dc 192.168.101.11 2019/02/12 02:30:38 [INFO] consul: Handled member-failed event for server "consul01.dc" in area "wan" 2019/02/12 02:30:39 [INFO] serf: EventMemberLeave: consul01 192.168.101.11在其它节点查看集群信息
[root@consul03 consul]# ./consul operator raft list-peersNode ID Address State Voter RaftProtocolconsul02 192.168.101.12:8300 192.168.101.12:8300 follower true 2consul03 192.168.101.13:8300 192.168.101.13:8300 leader true 2[root@consul03 consul]# ./consul membersNode Address Status Type Build Protocol DC Segmentconsul01 192.168.101.11:8301 left server 0.9.3 2 dc consul02 192.168.101.12:8301 alive server 0.9.3 2 dc consul03 192.168.101.13:8301 alive server 0.9.3 2 dc ...查看集群是否正常(查询注册服务，若没有服务可以通过consul api手动创建一个)
[root@consul03 consul]# ./consul catalog servicesconsultest-csdemo-v0-snapshottest-zuul-v0-snapshot可以看到，被停止的server节点处于left状态，但集群仍正常可用
因此，
server节点，不会影响consul集群服务```。
恢复此server节点```shell[root@consul03 consul]# ./consul operator raft list-peersNode ID Address State Voter RaftProtocolconsul02 192.168.101.12:8300 192.168.101.12:8300 follower true 2consul03 192.168.101.13:8300 192.168.101.13:8300 leader true 2consul01 192.168.101.11:8300 192.168.101.11:8300 follower true 2[root@consul03 consul]# ./consul membersNode Address Status Type Build Protocol DC Segmentconsul01 192.168.101.11:8301 alive server 0.9.3 2 dc consul02 192.168.101.12:8301 alive server 0.9.3 2 dc consul03 192.168.101.13:8301 alive server 0.9.3 2 dc ...其它节点已检测并将此节点加入
[root@consul02 ~]# tail -100 /var/log/consul 2019/02/12 02:43:51 [INFO] serf: EventMemberJoin: consul01.dc 192.168.101.11 2019/02/12 02:43:51 [INFO] consul: Handled member-join event for server "consul01.dc" in area "wan" 2019/02/12 02:43:51 [INFO] serf: EventMemberJoin: consul01 192.168.101.11 2019/02/12 02:43:51 [INFO] consul: Adding LAN server consul01 (Addr: tcp/192.168.101.11:8300) (DC: dc)§1. 停掉leader server节点
此处以consul03节点为例
[root@consul03 consul]# systemctl stop consul其它follow server节点检测到leader节点下线，并重新选举leader
[root@consul02 ~]# tail -100 /var/log/consul 2019/02/12 02:48:27 [INFO] serf: EventMemberLeave: consul03.dc 192.168.101.13 2019/02/12 02:48:27 [INFO] consul: Handled member-leave event for server "consul03.dc" in area "wan" 2019/02/12 02:48:28 [INFO] serf: EventMemberLeave: consul03 192.168.101.13 2019/02/12 02:48:28 [INFO] consul: Removing LAN server consul03 (Addr: tcp/192.168.101.13:8300) (DC: dc) 2019/02/12 02:48:37 [WARN] raft: Rejecting vote request from 192.168.101.11:8300 since we have a leader: 192.168.101.13:8300 2019/02/12 02:48:39 [ERR] agent: Coordinate update error: No cluster leader 2019/02/12 02:48:39 [WARN] raft: Heartbeat timeout from "192.168.101.13:8300" reached, starting election 2019/02/12 02:48:39 [INFO] raft: Node at 192.168.101.12:8300 [Candidate] entering Candidate state in term 5 2019/02/12 02:48:43 [ERR] http: Request GET /v1/catalog/services, error: No cluster leader from=127.0.0.1:44370 2019/02/12 02:48:43 [ERR] http: Request GET /v1/catalog/nodes, error: No cluster leader from=127.0.0.1:36548 2019/02/12 02:48:44 [INFO] raft: Node at 192.168.101.12:8300 [Follower] entering Follower state (Leader: "") 2019/02/12 02:48:44 [INFO] consul: New leader elected: consul01
可以从日志中看到，consul01已被选为新的leader，查看集群信息
[root@consul02 consul]# ./consul operator raft list-peersNode ID Address State Voter RaftProtocolconsul02 192.168.101.12:8300 192.168.101.12:8300 follower true 2consul01 192.168.101.11:8300 192.168.101.11:8300 leader true 2[root@consul02 consul]# ./consul membersNode Address Status Type Build Protocol DC Segmentconsul01 192.168.101.11:8301 alive server 0.9.3 2 dc consul02 192.168.101.12:8301 alive server 0.9.3 2 dc consul03 192.168.101.13:8301 left server 0.9.3 2 dc 可以看到，被停止的leader server节点处于left状态，但集群仍正常可用，查询服务验证
[root@consul02 consul]# ./consul catalog servicesconsultest-csdemo-v0-snapshottest-zuul-v0-snapshot因此，
server节点，也不会影响consul集群服务。
我们再恢复此节点到consul集群中```shell[root@consul03 consul]# systemctl start consul
可以通过它的日志看到它现在变成了follower server
[root@consul03 ~]# tail -f /var/log/consul 2019/02/12 03:01:33 [INFO] raft: Node at 192.168.101.13:8300 [Follower] entering Follower state (Leader: "") 2019/02/12 03:01:33 [INFO] serf: Ignoring previous leave in snapshot 2019/02/12 03:01:33 [INFO] agent: Retry join LAN is supported for: aws azure gce softlayer 2019/02/12 03:01:33 [INFO] agent: Joining LAN cluster... 2019/02/12 03:01:33 [INFO] agent: (LAN) joining: [consul01 consul02 consul03]新的leader和follower上也会更新节点信息
[root@consul01 ~]# tail -f /var/log/consul 2019/02/12 03:01:33 [INFO] serf: EventMemberJoin: consul03.dc 192.168.101.13 2019/02/12 03:01:33 [INFO] consul: Handled member-join event for server "consul03.dc" in area "wan" 2019/02/12 03:01:33 [INFO] serf: EventMemberJoin: consul03 192.168.101.13 2019/02/12 03:01:33 [INFO] consul: Adding LAN server consul03 (Addr: tcp/192.168.101.13:8300) (DC: dc) 2019/02/12 03:01:33 [INFO] raft: Updating configuration with AddStaging (192.168.101.13:8300, 192.168.101.13:8300) to [{Suffrage:Voter ID:192.168.101.12:8300 Address:192.168.101.12:8300} {Suffrage:Voter ID:192.168.101.11:8300 Address:192.168.101.11:8300} {Suffrage:Voter ID:192.168.101.13:8300 Address:192.168.101.13:8300}] 2019/02/12 03:01:33 [INFO] raft: Added peer 192.168.101.13:8300, starting replication 2019/02/12 03:01:33 [WARN] raft: AppendEntries to {Voter 192.168.101.13:8300 192.168.101.13:8300} rejected, sending older logs (next: 394016) 2019/02/12 03:01:33 [INFO] consul: member 'consul03' joined, marking health alive 2019/02/12 03:01:33 [INFO] raft: pipelining replication to peer {Voter 192.168.101.13:8300 192.168.101.13:8300}再次查看集群信息
[root@consul01 consul]# ./consul operator raft list-peersNode ID Address State Voter RaftProtocolconsul02 192.168.101.12:8300 192.168.101.12:8300 follower true 2consul01 192.168.101.11:8300 192.168.101.11:8300 leader true 2consul03 192.168.101.13:8300 192.168.101.13:8300 follower true 2[root@consul01 consul]# ./consul membersNode Address Status Type Build Protocol DC Segmentconsul01 192.168.101.11:8301 alive server 0.9.3 2 dc consul02 192.168.101.12:8301 alive server 0.9.3 2 dc consul03 192.168.101.13:8301 alive server 0.9.3 2 dc 集群各节点均已正常，此时仅leader角色改变，不影响集群对外提供服务。
