1 发现redis挂掉了，查看状态虽然为“active”

但是ps和netstat不查看不到，从日志中可以确认,报错信息

# WARNING overcommit_memory is set to 0! Background save may fail under low memory condition.
To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run
the command 'sysctl vm.overcommit_memory=1' for this to take effect.
# WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will
create latency and memory usage issues with Redis. To fix this issue run the command 'echo 
never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your/etc/rc.local in order to retain the setting after a reboot. 
Redis must be restarted after THP is disabled.

vm.overcommit_memory 内存分配策略
transparent_hugepage 透明大页 对mysql的影响

这两个参数的修改直接按照报错信息修改即可。