mysql-mmm故障解决一例
mysql-mmm故障解决一例关键字：FATAL Couldn't configure IP 'x.x.x.x' on interface 'eth1': undef
故障现象：
在mmm_monitor上ping agent的虚拟机ip，其中一个无法ping通
# mmm_control show
# Warning: agent on host db3 is not reachable
db1(10.1.1.15) master/ONLINE. Roles: reader(10.1.1.23), writer(10.1.1.20)
db2(10.1.1.14) master/ONLINE. Roles: reader(10.1.1.22)
db3(10.1.1.13) slave/ONLINE. Roles: reader(10.1.1.21)
# Role writer is assigned to it's preferred host db1.
# ping 10.1.1.21
PING 10.1.1.21 (10.1.1.21) 56(84) bytes of data.
From 10.1.1.12 icmp_seq=2 Destination Host Unreachable
From 10.1.1.12 icmp_seq=3 Destination Host Unreachable
From 10.1.1.12 icmp_seq=4 Destination Host Unreachable
--- 10.1.1.21 ping statistics ---
4 packets transmitted, 0 received, +3 errors, 100% packet loss, time 2998ms
, pipe 3
# ping 10.1.1.22
PING 10.1.1.22 (10.1.1.22) 56(84) bytes of data.
64 bytes from 10.1.1.22: icmp_seq=1 ttl=64 time=0.102 ms
--- 10.1.1.22 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.102/0.102/0.102/0.000 ms
在db3的实体机 10.1.1.13上：
查看是否有此IP，结果此IP没有被设置到此机器
# ip add
1: lo:mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0:mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:80:3f:03:47:ce brd ff:ff:ff:ff:ff:ff
inet 6.6.6.6/28 brd 122.225.32.143 scope global eth0
inet6 fe80::280:3fff:fe03:47ce/64 scope link
valid_lft forever preferred_lft forever
3: eth1:mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:80:3f:03:47:cf brd ff:ff:ff:ff:ff:ff
inet 10.1.1.13/24 brd 10.1.1.255 scope global eth1
inet6 fe80::280:3fff:fe03:47cf/64 scope link
valid_lft forever preferred_lft forever
4: sit0:mtu 1480 qdisc noop
link/sit 0.0.0.0 brd 0.0.0.0
查看mysql-mmm-agent的日志
2011/06/02 20:07:50INFO Changing active master to 'db1'
2011/06/02 20:07:50 FATAL Failed to change master to 'db1': undef
2011/06/02 20:07:50 FATAL Couldn't configure IP '10.1.1.21' on interface 'eth1': undef
根据mysql-mmm-agent的日志，通过google找到了解决问题的方法
# /usr/lib/mysql-mmm/agent/configure_ip eth1 10.1.1.21
Can't locate Net/ARP.pm in @INC (@INC contains: /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 .) at /usr/lib/perl5/vendor_perl/5.8.8/MMM/Agent/Helpers/Network.pm line 11.
BEGIN failed--compilation aborted at /usr/lib/perl5/vendor_perl/5.8.8/MMM/Agent/Helpers/Network.pm line 11.
Compilation failed in require at /usr/lib/perl5/vendor_perl/5.8.8/MMM/Agent/Helpers/Actions.pm line 5.
BEGIN failed--compilation aborted at /usr/lib/perl5/vendor_perl/5.8.8/MMM/Agent/Helpers/Actions.pm line 5.
Compilation failed in require at /usr/lib/mysql-mmm/agent/configure_ip line 6.
BEGIN failed--compilation aborted at /usr/lib/mysql-mmm/agent/configure_ip line 6.
原来是arp.pm没有安装，我们现在就来安装它
# perl -MCPAN -e shell
cpan> install Net::ARP
安装完成以后通过mmm_monitor将db3置于离线，在置于在线，测试是否可以ping通。
# mmm_control set_offline db3
OK: State of 'db3' changed to ADMIN_OFFLINE. Now you can wait some time and check all roles!
# mmm_control set_online db3
OK: State of 'db3' changed to ONLINE. Now you can wait some time and check its new roles!
# mmm_control show
db1(10.1.1.15) master/ONLINE. Roles: reader(10.1.1.23), writer(10.1.1.20)
db2(10.1.1.14) master/ONLINE. Roles: reader(10.1.1.22)
db3(10.1.1.13) slave/ONLINE. Roles: reader(10.1.1.21)
# Role writer is assigned to it's preferred host db1.
# ping 10.1.1.21
PING 10.1.1.21 (10.1.1.21) 56(84) bytes of data.
64 bytes from 10.1.1.21: icmp_seq=1 ttl=64 time=0.181 ms
64 bytes from 10.1.1.21: icmp_seq=2 ttl=64 time=0.079 ms
问题解决了。
最后总结一下：
这个问题其实是安装时候不小心遗留下来的，由于db3是纯slave，所以一般是通过真实ip去访问，没有用到虚拟IP，mmm_monitor也完全没有表现出任何的故障信息。问题是在配置读写分离时候，用到了slave的虚拟IP，才发现的。
所以在需要上线的架构，最好还是安装官方文档，一一检查清楚，避免不必要的故障。
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