基于Consul的数据库高可用架构

consul server：192.168.0.10

consul client：192.168.0.20，192.168.0.30，192.168.0.40

 consul的安装非常容易，从https://www.consul.io/downloads.html这里下载以后，解压即可使用，就是一个二进制文件，其他的都没有了。我这里使用的是0.92版本。文件下载以后解压放到/usr/local/bin。就可以使用了。不依赖任何东西。上面的4台服务器都安装。

4台机器都创建目录，分别是放配置文件，以及存放数据的。以及存放redis，mysql的健康检查脚本

mkdir /etc/consul.d/ -p && mkdir /data/consul/ -p

mkidr /data/consul/shell -p

然后把相关配置参数写入配置文件，其实也可以不用写，直接跟在命令后面就行，那样不方便管理。
consul server（192.168.0.10）配置文件（具体参数的意思请查询官网或者文章给的参考链接）：

[root@db-server-yayun-01 ~]# cat /etc/consul.d/server.json 
{
  "data_dir": "/data/consul",
  "datacenter": "dc1",
  "log_level": "INFO",
  "server": true,
  "bootstrap_expect": 1,
  "bind_addr": "192.168.0.10",
  "client_addr": "192.168.0.10",
  "ui":true
}
[root@db-server-yayun-01 ~]# 

consul client（192.168.0.20,192.168.0.30,192.168.0.40）

[root@db-server-yayun-02 ~]# cat /etc/consul.d/client.json 
{
  "data_dir": "/data/consul",
  "enable_script_checks": true,
  "bind_addr": "192.168.0.20",
  "retry_join": ["192.168.0.10"],
  "retry_interval": "30s",
  "rejoin_after_leave": true,
  "start_join": ["192.168.0.10"]
}
[root@db-server-yayun-02 ~]# 

3台服务器的配置文件差异不大，唯一有区别的就是bind_addr地方，自行修改为你自己服务器的ip。我测试环境是虚拟机，有多快网卡，所以必须指定，否则可以绑定0.0.0.0。
下面我们先启动consul server：

nohup consul agent -config-dir=/etc/consul.d > /data/consul/consul.log &

 查看日志：

[root@db-server-yayun-01 consul]# cat consul.log 
==> WARNING: BootstrapExpect Mode is specified as 1; this is the same as Bootstrap mode.
==> WARNING: Bootstrap mode enabled! Do not enable unless necessary
==> Starting Consul agent...
==> Consul agent running!
           Version: ‘v0.9.2‘
           Node ID: ‘5e612623-ec5b-386c-19be-d38876a9a46f‘
         Node name: ‘db-server-yayun-01‘
        Datacenter: ‘dc1‘
            Server: true (bootstrap: true)
       Client Addr: 192.168.0.10 (HTTP: 8500, HTTPS: -1, DNS: 8600)
      Cluster Addr: 192.168.0.10 (LAN: 8301, WAN: 8302)
    Gossip encrypt: false, RPC-TLS: false, TLS-Incoming: false

==> Log data will now stream in as it occurs:

    2017/12/09 09:49:53 [INFO] raft: Initial configuration (index=1): [{Suffrage:Voter ID:192.168.0.10:8300 Address:192.168.0.10:8300}]
    2017/12/09 09:49:53 [INFO] raft: Node at 192.168.0.10:8300 [Follower] entering Follower state (Leader: "")
    2017/12/09 09:49:53 [INFO] serf: EventMemberJoin: db-server-yayun-01.dc1 192.168.0.10
    2017/12/09 09:49:53 [INFO] serf: EventMemberJoin: db-server-yayun-01 192.168.0.10
    2017/12/09 09:49:53 [INFO] agent: Started DNS server 192.168.0.10:8600 (udp)
    2017/12/09 09:49:53 [INFO] consul: Adding LAN server db-server-yayun-01 (Addr: tcp/192.168.0.10:8300) (DC: dc1)
    2017/12/09 09:49:53 [INFO] consul: Handled member-join event for server "db-server-yayun-01.dc1" in area "wan"
    2017/12/09 09:49:53 [INFO] agent: Started DNS server 192.168.0.10:8600 (tcp)
    2017/12/09 09:49:53 [INFO] agent: Started HTTP server on 192.168.0.10:8500
    2017/12/09 09:50:00 [ERR] agent: failed to sync remote state: No cluster leader
    2017/12/09 09:50:00 [WARN] raft: Heartbeat timeout from "" reached, starting election
    2017/12/09 09:50:00 [INFO] raft: Node at 192.168.0.10:8300 [Candidate] entering Candidate state in term 2
    2017/12/09 09:50:00 [INFO] raft: Election won. Tally: 1
    2017/12/09 09:50:00 [INFO] raft: Node at 192.168.0.10:8300 [Leader] entering Leader state
    2017/12/09 09:50:00 [INFO] consul: cluster leadership acquired
    2017/12/09 09:50:00 [INFO] consul: New leader elected: db-server-yayun-01
    2017/12/09 09:50:00 [INFO] consul: member ‘db-server-yayun-01‘ joined, marking health alive
    2017/12/09 09:50:03 [INFO] agent: Synced node info

 可以从日志中看到(HTTP: 8500, HTTPS: -1, DNS: 8600)，http端口默认8500，在reload以及web ui会用到，dns端口是8600，在使用dns解析的时候会用到。还可以看到这台机器就是leader，consul: New leader elected: db-server-yayun-01。因为只有一台机器。所以生产环境一定要3个或者5个server。

下面启动3台client，3台client启动命令是一样的。然后查看其中一台client的日志：

nohup consul agent -config-dir=/etc/consul.d > /data/consul/consul.log &

[root@db-server-yayun-02 consul]# cat /data/consul/consul.log 
==> Starting Consul agent...
==> Joining cluster...
    Join completed. Synced with 1 initial agents
==> Consul agent running!
           Version: ‘v0.9.2‘
           Node ID: ‘0ec901ab-6c66-2461-95e6-50a77a28ed72‘
         Node name: ‘db-server-yayun-02‘
        Datacenter: ‘dc1‘
            Server: false (bootstrap: false)
       Client Addr: 127.0.0.1 (HTTP: 8500, HTTPS: -1, DNS: 8600)
      Cluster Addr: 192.168.0.20 (LAN: 8301, WAN: 8302)
    Gossip encrypt: false, RPC-TLS: false, TLS-Incoming: false

==> Log data will now stream in as it occurs:

    2017/12/09 10:06:10 [INFO] serf: EventMemberJoin: db-server-yayun-02 192.168.0.20
    2017/12/09 10:06:10 [INFO] agent: Started DNS server 127.0.0.1:8600 (udp)
    2017/12/09 10:06:10 [INFO] agent: Started DNS server 127.0.0.1:8600 (tcp)
    2017/12/09 10:06:10 [INFO] agent: Started HTTP server on 127.0.0.1:8500
    2017/12/09 10:06:10 [INFO] agent: (LAN) joining: [192.168.0.10]
    2017/12/09 10:06:10 [INFO] agent: Retry join is supported for: aws azure gce softlayer
    2017/12/09 10:06:10 [INFO] agent: Joining cluster...
    2017/12/09 10:06:10 [INFO] agent: (LAN) joining: [192.168.0.10]
    2017/12/09 10:06:10 [INFO] serf: EventMemberJoin: db-server-yayun-01 192.168.0.10
    2017/12/09 10:06:10 [INFO] agent: (LAN) joined: 1 Err: <nil>
    2017/12/09 10:06:10 [INFO] consul: adding server db-server-yayun-01 (Addr: tcp/192.168.0.10:8300) (DC: dc1)
    2017/12/09 10:06:10 [INFO] agent: (LAN) joined: 1 Err: <nil>
    2017/12/09 10:06:10 [INFO] agent: Join completed. Synced with 1 initial agents
    2017/12/09 10:06:10 [INFO] agent: Synced node info

可以看到提示agent: Join completed. Synced with 1 initial agents，以及Server: false (bootstrap: false)。这也是client和server的区别。
我们继续执行命令看一下集群：

[root@db-server-yayun-02 ~]# consul members
Node                Address            Status  Type    Build  Protocol  DC
db-server-yayun-01  192.168.0.10:8301  alive   server  0.9.2  2         dc1
db-server-yayun-02  192.168.0.20:8301  alive   client  0.9.2  2         dc1
db-server-yayun-03  192.168.0.30:8301  alive   client  0.9.2  2         dc1
db-server-yayun-04  192.168.0.40:8301  alive   client  0.9.2  2         dc1
[root@db-server-yayun-02 ~]# 

[root@db-server-yayun-02 ~]# consul operator raft list-peers
Node                ID                 Address            State   Voter  RaftProtocol
db-server-yayun-01  192.168.0.10:8300  192.168.0.10:8300  leader  true   2
[root@db-server-yayun-02 ~]# 

我们看看web ui，consul自带的ui，非常轻便。访问：http://192.168.0.10:8500/ui/

到这来consul集群就搭建完成了，是不是很简单。对就是这么简单，但是从上面可以看到，client节点并没有注册服务，显示0 services。这也就是接下来需要讲解的。那么到底如何实现redis及mysql的高可用呢？正式开始：

Consul 使用场景一（redis sentinel）
(1)Redis 哨兵架构下,服务器部署了哨兵,但业务部门没有在app 层面,使用jedis 哨兵驱动来自动发现Redis master,而使用直连IP master。当master挂掉，其他redis节点担当新master后，应用需要手工修改配置，指向新master。
(2)Redis 客户端驱动,还没有读写分离的配置，若想slave的读负载均衡，暂时没好的办法。我们程序都是支持读写分离，所以没影响
(3)Consul 可以满足以上需求，配置两个DNS服务，一个是master的服务，利用consul自身的服务健康检查和探测功能， 自动发现新的master。 然后定义一个slave的服务，基于DNS本身， 能够对slave角色的redis IP做轮询。

架构图如下：

同样也可以对mysql做高可用，mha和sentinel的角色一样，架构图如下：

下面就说说redis高可用的实现过程，mysql的我就不说了，mysql用到的健康检查脚本我会贴出来。思路都是一样的。

Consul 服务定义（Redis）

上面已经搭建好了consul集群，server是192.168.0.10 client是20到40. 那么20我们就拿来当redis master，30,40拿来当redis slave。下面定义服务（20,30,40都要存在）：

20,30,40的配置文件如下，除了address要修改为对应的服务器地址，其他一样。

[root@db-server-yayun-02 consul.d]# pwd
/etc/consul.d
[root@db-server-yayun-02 consul.d]# ll
total 12
-rw-r--r--. 1 root root 221 Dec  9 09:44 client.json
-rw-r--r--. 1 root root 319 Dec  9 10:48 r-6029-redis-test.json
-rw-r--r--. 1 root root 321 Dec  9 10:48 w-6029-redis-test.json
[root@db-server-yayun-02 consul.d]# 

master的服务定义配置文件：

[root@db-server-yayun-02 consul.d]# cat w-6029-redis-test.json 
{
  "services": [
    {
      "name": "w-6029-redis-test",
      "tags": [
        "master-test-6029"
      ],
      "address": "192.168.0.20",
      "port": 6029,
      "checks": [
        {
          "script": "/data/consul/shell/check_redis_master.sh 6029 ",
          "interval": "15s"
        }
      ]
    }
  ]
}

[root@db-server-yayun-02 consul.d]# 

slave的服务定义配置文件：

[root@db-server-yayun-02 consul.d]# cat r-6029-redis-test.json 
{
  "services": [
    {
      "name": "r-6029-redis-test",
      "tags": [
        "slave-test-6029"
      ],
      "address": "192.168.0.20",
      "port": 6029,
      "checks": [
        {
          "script": "/data/consul/shell/check_redis_slave.sh 6029 ",
          "interval": "15s"
        }
      ]
    }
  ]
}

[root@db-server-yayun-02 consul.d]# 

每个agent都注册后， 对应有两个域名:
w-6029-redis-test.service.consul （对应唯一一个master IP）
r-6029-redis-test.service.consul  (对应两个slave IP， 客户端请求时， 随机分配一个）

其中"script": "/data/consul/shell/check_redis_slave.sh 6029 "代表对redis 6029端口进行健康检查，关于更多健康检查请查看官网介绍。

[root@db-server-yayun-03 shell]# pwd
/data/consul/shell
[root@db-server-yayun-03 shell]# ll
total 16
-rwxr-xr-x. 1 root root  480 Dec  9 10:56 check_mysql_master.sh
-rwxr-xr-x. 1 root root 3004 Dec  9 10:55 check_mysql_slave.sh
-rwxr-xr-x. 1 root root  254 Dec  9 10:51 check_redis_master.sh
-rwxr-xr-x. 1 root root  379 Dec  9 10:51 check_redis_slave.sh
[root@db-server-yayun-03 shell]# 

/data/consul/shell目录下面有4个脚本，是对redis和mysql进行健康检查用的。脚本比较简单，大概就是如果只有一个master，那么读写都在master，如果有slave可用，那么读会在slave进行。如果slave复制不正常，或者复制延时，那么服务将不会注册。

[root@db-server-yayun-03 shell]# cat check_redis_master.sh 
#!/bin/bash
myport=$1
auth=$2
if [ ! -n "$auth" ]
then
auth=‘\"\"‘
fi
comm="/usr/local/bin/redis-cli -p $myport -a $auth "
role=`echo ‘INFO Replication‘|$comm |grep -Ec ‘role:master‘`
echo ‘INFO Replication‘|$comm

if [ $role -ne 1 ]
then
    exit 2
fi

[root@db-server-yayun-03 shell]# 

[root@db-server-yayun-03 shell]# cat check_redis_slave.sh 
#!/bin/bash
myport=$1
auth=$2
if [ ! -n "$auth" ]
then
auth=‘\"\"‘
fi
comm="/usr/local/bin/redis-cli -p $myport -a $auth "
role=`echo ‘INFO Replication‘|$comm |grep -Ec ‘^role:slave|^master_link_status:up‘`
single=`echo ‘INFO Replication‘|$comm |grep -Ec ‘^role:master|^connected_slaves:0‘`
echo ‘INFO Replication‘|$comm

if [ $role -ne 2 -a $single -ne 2  ]
then
    exit 2
fi

[root@db-server-yayun-03 shell]# 

[root@db-server-yayun-03 shell]# cat check_mysql_master.sh 
#!/bin/bash
port=$1
user="root"
passwod="123"

comm="/usr/local/mysql/bin/mysql -u$user -h 127.0.0.1 -P $port -p$passwod"
slave_info=`$comm -e "show slave status" |wc -l`
value=`$comm -Nse "select 1"`

# 判断是不是从库
if [ $slave_info -ne 0 ]
then
   exit 2
fi


# 判断mysql是否存活
if [ -z $value ]
then
   exit 2
fi

echo "MySQL $port  Instance is Master........"
$comm -e "select * from information_schema.PROCESSLIST where user=‘repl‘ and COMMAND like ‘%Dump%‘"
[root@db-server-yayun-03 shell]# 

[root@db-server-yayun-03 shell]# cat check_mysql_slave.sh 
#!/bin/bash
port=$1
user="root"
passwod="123"
repl_check_user="root"
repl_check_pwd="123"

master_comm="/usr/local/mysql/bin/mysql -u$user -h 127.0.0.1 -P $port -p$passwod"
slave_comm="/usr/local/mysql/bin/mysql -u$repl_check_user  -P $port -p$repl_check_pwd"

# 判断mysql是否存活
value=`$master_comm -Nse "select 1"`
if [ -z $value ]
then
   echo "MySQL Server is Down....."
   exit 2
fi

get_slave_count=0
is_slave_role=0
slave_mode_repl_delay=0
master_mode_repl_delay=0
master_mode_repl_dead=0
slave_mode_repl_status=0
max_delay=120

get_slave_hosts=`$master_comm -Nse "select substring_index(HOST,‘:‘,1) from information_schema.PROCESSLIST where user=‘repl‘ and COMMAND=‘Binlog Dump‘;" `
get_slave_count=`$master_comm -Nse "select count(1) from information_schema.PROCESSLIST where user=‘repl‘ and COMMAND=‘Binlog Dump‘;" `
is_slave_role=`$master_comm -e "show slave status\G"|grep -Ewc "Slave_SQL_Running|Slave_IO_Running"`


### 单点模式(如果 get_slave_count=0 and is_slave_role=0)
function single_mode
{
if [ $get_slave_count -eq 0 -a $is_slave_role -eq 0 ]
then
    echo "MySQL $port  Instance is Single Master........"
    exit 0 
fi
}

### 从节点模式(如果 get_slave_count=0 and is_slave_role=2 ) 
function slave_mode
{
#如果是从节点,必须满足不延迟,
if [  $is_slave_role -ge 2 ]
then
        echo "MySQL $port  Instance is Slave........"
        $master_comm -e "show slave status\G" | egrep -w "Master_Host|Master_User|Master_Port|Master_Log_File|Read_Master_Log_Pos|Relay_Log_File|Relay_Log_Pos|Relay_Master_Log_File|Slave_IO_Running|Slave_SQL_Running|Exec_Master_Log_Pos|Relay_Log_Space|Seconds_Behind_Master"
        slave_mode_repl_delay=`$master_comm -e "show slave status\G" | grep -w "Seconds_Behind_Master" | awk ‘{print $NF}‘`
        slave_mode_repl_status=`$master_comm -e "show slave status\G"|grep -Ec "Slave_IO_Running: Yes|Slave_SQL_Running: Yes"`
if [ X"$slave_mode_repl_delay" == X"NULL" ]
then
        slave_mode_repl_delay=99999
fi
        if [ $slave_mode_repl_delay != "NULL" -a $slave_mode_repl_delay -lt $max_delay -a $slave_mode_repl_status -ge 2 ] 
        then
             exit 0
        fi
fi
} 

function master_mode
{
###如果是主节点，必须满足从节点为延迟或复制错误。才可读
if [ $get_slave_count -gt 0 -a $is_slave_role -eq  0 ]
then
    echo "MySQL $port  Instance is Master........"
    $master_comm -e "select * from information_schema.PROCESSLIST where user=‘repl‘ and COMMAND like ‘%Dump%‘"
    for my_slave in $get_slave_hosts
do 
master_mode_repl_delay=`$slave_comm -h $my_slave -e "show slave status\G" | grep -w "Seconds_Behind_Master" | awk ‘{print $NF}‘ `
master_mode_repl_thread=`$slave_comm -h $my_slave -e "show slave status\G"|grep -Ec "Slave_IO_Running: Yes|Slave_SQL_Running: Yes"`
if [ X"$master_mode_repl_delay" == X"NULL" ]
then
     master_mode_repl_delay=99999
fi

if [ $master_mode_repl_delay -lt $max_delay -a $master_mode_repl_thread -ge 2 ]
then
    exit 2
fi
done 
exit 0
fi
} 

single_mode
slave_mode
master_mode
exit 2
[root@db-server-yayun-03 shell]# 

"name": "r-6029-redis-test",这个就是域名了，默认后缀是servers.consul，consul可以利用domain参数修改。配置文件生成以后安装redis，搭建主从复制（省略）。主从复制完成以后就可以重新reload consul了。redis info信息：

127.0.0.1:6029> info replication
# Replication
role:master
connected_slaves:2
slave0:ip=192.168.0.40,port=6029,state=online,offset=6786,lag=0
slave1:ip=192.168.0.30,port=6029,state=online,offset=6786,lag=1
master_repl_offset:6786
repl_backlog_active:1
repl_backlog_size:67108864
repl_backlog_first_byte_offset:2
repl_backlog_histlen:6785
127.0.0.1:6029> 

reload consul（3台client，也就是20-40）：

[root@db-server-yayun-02 ~]# consul reload
Configuration reload triggered
[root@db-server-yayun-02 ~]# 

在其中一台服务器查看consul日志（20）：

[root@db-server-yayun-02 consul]# tail -f consul.log 
    2017/12/09 10:09:59 [INFO] serf: EventMemberJoin: db-server-yayun-04 192.168.0.40
    2017/12/09 11:14:55 [INFO] Caught signal:  hangup
    2017/12/09 11:14:55 [INFO] Reloading configuration...
    2017/12/09 11:14:55 [INFO] agent: Synced service ‘r-6029-redis-test‘
    2017/12/09 11:14:55 [INFO] agent: Synced service ‘w-6029-redis-test‘
    2017/12/09 11:14