问题解决-ubuntu启动redis-server报错

问题

ubuntu启动redis-server报错。

查看redis运行日志cat /var/log/redis/redis-server.log，发现以下告警信息：

1888:M 27 Feb 2020 07:42:29.235 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1888:M 27 Feb 2020 07:42:29.235 # Server initialized
1888:M 27 Feb 2020 07:42:29.235 # 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.
1888:M 27 Feb 2020 07:42:29.235 # 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.

解决方法

使用root用户进行以下操作：

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echo 511 > /proc/sys/net/core/somaxconn
echo "vm.overcommit_memory=1" > /etc/sysctl.conf
echo never > /sys/kernel/mm/transparent_hugepage/enabled

之后重启redis-server：service redis-server restart。

新的问题

远程连接运行redis命令，发现如下报错：

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192.168.80.17:6379> ping
(error) DENIED Redis is running in protected mode because protected mode is enabled, no bind address was specified, no authentication password is requested to clients. In this mode connections are only accepted from the loopback interface. If you want to connect from external computers to Redis you may adopt one of the following solutions: 1) Just disable protected mode sending the command 'CONFIG SET protected-mode no' from the loopback interface by connecting to Redis from the same host the server is running, however MAKE SURE Redis is not publicly accessible from internet if you do so. Use CONFIG REWRITE to make this change permanent. 2) Alternatively you can just disable the protected mode by editing the Redis configuration file, and setting the protected mode option to 'no', and then restarting the server. 3) If you started the server manually just for testing, restart it with the '--protected-mode no' option. 4) Setup a bind address or an authentication password. NOTE: You only need to do one of the above things in order for the server to start accepting connections from the outside.

解决方法：
修改配置文件vi /etc/redis/redis.conf：
将protected-mode yes改为protected-mode no，之后重启redis-server：service redis-server restart。

但是不知道为什么重启redis-server老报错：（这种情况下，redis数据库却能正常使用）

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root@dana:~# service redis-server restart
Job for redis-server.service failed because a timeout was exceeded.
See "systemctl status redis-server.service" and "journalctl -xe" for details.

redis服务正常：

1 2	root@dana:~# ps aux \|grep 6379 redis 3107 0.3 0.3 50092 6644 ? Ssl 08:38 0:00 /usr/bin/redis-server *:6379

参考博文

https://blog.51cto.com/sf1314/2156127