redis持久化问题处理

这个是最近在开发的过程中遇到的问题，因为需要频繁使用redis作为中间查询操作，突然故障了，服务中止，然后抛出异常

2020-01-09 09:34:17.848 ERROR 25703 --- [ XNIO-2 task-83] o.z.p.spring.web.advice.AdviceTrait      : Internal Server Error

org.springframework.data.redis.RedisSystemException: Error in execution; nested exception is io.lettuce.core.RedisCommandExecutionException: MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.

    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:54)
    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:52)
    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:41)
    at org.springframework.data.redis.PassThroughExceptionTranslationStrategy.translate(PassThroughExceptionTranslationStrategy.java:44)
    at org.springframework.data.redis.FallbackExceptionTranslationStrategy.translate(FallbackExceptionTranslationStrategy.java:42)
    at org.springframework.data.redis.connection.lettuce.LettuceConnection.convertLettuceAccessException(LettuceConnection.java:257)
    at org.springframework.data.redis.connection.lettuce.LettuceHashCommands.convertLettuceAccessException(LettuceHashCommands.java:445)
    at org.springframework.data.redis.connection.lettuce.LettuceHashCommands.hSet(LettuceHashCommands.java:70)
    at org.springframework.data.redis.connection.DefaultedRedisConnection.hSet(DefaultedRedisConnection.java:827)
    at org.springframework.data.redis.connection.DefaultStringRedisConnection.hSet(DefaultStringRedisConnection.java:501)
    at org.springframework.data.redis.core.DefaultHashOperations.lambda$put$8(DefaultHashOperations.java:178)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:224)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:184)
    at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:95)
    at org.springframework.data.redis.core.DefaultHashOperations.put(DefaultHashOperations.java:177)
    at com.smpteam.aaaa.service.impl.RedisServiceImpl.setESSession(RedisServiceImpl.java:59)
    at com.smpteam.aaaa.service.impl.RedisServiceImpl$$FastClassBySpringCGLIB$$11b51629.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    . . .
Caused by: io.lettuce.core.RedisCommandExecutionException: MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.

然后我通过redis-cli登录redis服务器检查情况，发现ping不通

(error) MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.
这提示及其友好，虽长但我喜欢：）

Redis问题

MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.

Redis被配置为保存数据库快照，但它目前不能持久化到硬盘。用来修改集合数据的命令不能用。请查看Redis日志的详细错误信息。

原因

强制关闭Redis快照导致不能持久化。本质上是内存不足导致的。因此需要进行相关的内存处理：

1. 修改redis config
2. 修改快照备份的目录，即将快照重定向到其他目录
3. 修改主机内存配置

解决方案1

将stop-writes-on-bgsave-error设置为no，这个方式是直接关闭保存持久化快照

127.0.0.1:6379> config set stop-writes-on-bgsave-error no

这个在生产中可能会出现一些问题，这个然而这个方法治标不治本，他只是让我们“忽略”他而已，使用之前需要确认bgsave失败的原因，比如当redis用于缓存、会话的场景的时候，这么做是允许的

解决方案2

将备份的rdb文件，重定向到目录

CONFIG SET dir /tmp/some/directory/other/than/var
CONFIG SET dbfilename temp.rdb

使用这个命令之后，需要确保bgsave_in_progress返回结果是0

解决方案3

在内核运行时动态地修改内核的运行参数

echo 'vm.overcommit_memory = 1' >> /etc/sysctl.conf
sysctl vm.overcommit_memory=1