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机制以及应对方案。影响Redis性能的五大方面的潜在因素DAR

2021-01-13 23:58:33  阅读:104  来源: 互联网

标签:www http Redis html DAR 五大 com book itangyuan


Redis被广泛使用的一个很重要的原因是它的高性能。因此我们必要要重视所有可能影响Redis性能的因素、机制以及应对方案。影响Redis性能的五大方面的潜在因素,分别是:

Redis内部的阻塞式操作
CPU核和NUMA架构的影响
Redis关键系统配置
Redis内存碎片
Redis缓冲区
在前面的2讲中,学习了会导致Redis变慢的潜在阻塞点以及相应的解决方案,即异步线程机制和CPU绑核。除此之外,还有一些因素会导致Redis变慢。

这一讲,介绍如何系统性应对Redis变慢这个问题。从问题认定、系统性排查和应对方案这3个方面来讲解。

判断Redis是否变慢?
最直接的方法,查看Redis的响应延迟。通过绝对值来判断,比如执行时间突然增长到几秒。

但是这个方法在不同配置的机器上的误差比较大。第二个方法是基于当前环境下的Redis基线性能做判断。

基线性能指一个系统在低压力、无干扰下的基本性能。

怎么确定基线性能?从2.8.7版本开始,redis-cli命令提供了-intrinsic-latency选项,可以用来监测和统计测试期间内的最大延迟,这个延迟可以作为Redis的基线性能。其中,测试时长可以用-intrinsic-latency选项的参数来指定。

一般来说,运行时延和基线性能对比,如果运行时延是基线性能的2倍及以上时,就可以认定Redis变慢了。为了避免网络对基线性能的影响,直接在服务器端运行。

如何应对Redis变慢?
影响Redis的关键因素有三个:Redis自身的操作特性、文件系统和操作系统。

Redis自身操作特性的影响
Redis有两个操作会对性能造成较大影响,分别是慢查询命令和过期key操作。

慢查询命令
慢查询命令,就是指在Redis中执行速度慢的命令,这会导致Redis延迟增加。

排查:通过Redis日志、或者是latency monitor工具。

解决方法:

用其他高效命令代替。比如不要使用SMEMBERS命令,而是用SSCAN多次迭代返回;
当需要执行排序、交集、并集操作时,可以在客户端完成,而不要用SORT、SUNION、SINTER这些命令。
还有一个比较容易遗漏的慢查询命令是KEYS命令,它用于返回和输入模式的所有key。因为KEYS命令需要遍历存储的键值对,所以操作延时高。KEYS命令一般不被建议用于生产环境中。

过期key操作
过期key的自动删除机制,它是Redis用来回收内存空间的常用机制,本身会引起Redis操作阻塞,导致性能变慢。

排查:检查业务代码在使用EXPIREAT命令设置key过期时间时,是否使用了相同的UNIX时间戳。因为这会造成大量key在同一时间过期,导致性能变慢。

解决方法:

根据实际业务需求来决定EXPIREAT和EXPIRE的过期时间参数。
如果一批key的确是同时过期,可以在EXPIREAT和EXPIRE的过期时间参数上,加上一个一定大小范围内的随机参数
文件系统的影响
在基础篇讲过,为了保证数据可靠性,Redis会采用AOF日志或者RDB快照。其中,AOF日志提供了三种日志写回策略:no、everysec、always。这三种写回策略依赖文件系统的两个系统调用完成:write和fsync。

write只要把日志记录写到内核缓冲区即可;Redis被广泛使用的一个很重要的原因是它的高性能。因此我们必要要重视所有可能影响Redis性能的因素、机制以及应对方案。影响Redis性能的五大方面的潜在因素,分别是:

Redis内部的阻塞式操作
CPU核和NUMA架构的影响
Redis关键系统配置
Redis内存碎片
Redis缓冲区
在前面的2讲中,学习了会导致Redis变慢的潜在阻塞点以及相应的解决方案,即异步线程机制和CPU绑核。除此之外,还有一些因素会导致Redis变慢。

这一讲,介绍如何系统性应对Redis变慢这个问题。从问题认定、系统性排查和应对方案这3个方面来讲解。

判断Redis是否变慢?
最直接的方法,查看Redis的响应延迟。通过绝对值来判断,比如执行时间突然增长到几秒。
Redis被广泛使用的一个很重要的原因是它的高性能。因此我们必要要重视所有可能影响Redis性能的因素、机制以及应对方案。影响Redis性能的五大方面的潜在因素,分别是:

Redis内部的阻塞式操作
CPU核和NUMA架构的影响
Redis关键系统配置
Redis内存碎片
Redis缓冲区
在前面的2讲中,学习了会导致Redis变慢的潜在阻塞点以及相应的解决方案,即异步线程机制和CPU绑核。除此之外,还有一些因素会导致Redis变慢。

这一讲,介绍如何系统性应对Redis变慢这个问题。从问题认定、系统性排查和应对方案这3个方面来讲解。

判断Redis是否变慢?
最直接的方法,查看Redis的响应延迟。通过绝对值来判断,比如执行时间突然增长到几秒。

但是这个方法在不同配置的机器上的误差比较大。第二个方法是基于当前环境下的Redis基线性能做判断。

基线性能指一个系统在低压力、无干扰下的基本性能。

怎么确定基线性能?从2.8.7版本开始,redis-cli命令提供了-intrinsic-latency选项,可以用来监测和统计测试期间内的最大延迟,这个延迟可以作为Redis的基线性能。其中,测试时长可以用-intrinsic-latency选项的参数来指定。

一般来说,运行时延和基线性能对比,如果运行时延是基线性能的2倍及以上时,就可以认定Redis变慢了。为了避免网络对基线性能的影响,直接在服务器端运行。

如何应对Redis变慢?
影响Redis的关键因素有三个:Redis自身的操作特性、文件系统和操作系统。

Redis自身操作特性的影响
Redis有两个操作会对性能造成较大影响,分别是慢查询命令和过期key操作。

慢查询命令
慢查询命令,就是指在Redis中执行速度慢的命令,这会导致Redis延迟增加。

排查:通过Redis日志、或者是latency monitor工具。

解决方法:

用其他高效命令代替。比如不要使用SMEMBERS命令,而是用SSCAN多次迭代返回;
当需要执行排序、交集、并集操作时,可以在客户端完成,而不要用SORT、SUNION、SINTER这些命令。
还有一个比较容易遗漏的慢查询命令是KEYS命令,它用于返回和输入模式的所有key。因为KEYS命令需要遍历存储的键值对,所以操作延时高。KEYS命令一般不被建议用于生产环境中。

过期key操作
过期key的自动删除机制,它是Redis用来回收内存空间的常用机制,本身会引起Redis操作阻塞,导致性能变慢。

排查:检查业务代码在使用EXPIREAT命令设置key过期时间时,是否使用了相同的UNIX时间戳。因为这会造成大量key在同一时间过期,导致性能变慢。

解决方法:
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根据实际业务需求来决定EXPIREAT和EXPIRE的过期时间参数。
如果一批key的确是同时过期,可以在EXPIREAT和EXPIRE的过期时间参数上,加上一个一定大小范围内的随机参数
文件系统的影响
在基础篇讲过,为了保证数据可靠性,Redis会采用AOF日志或者RDB快照。其中,AOF日志提供了三种日志写回策略:no、everysec、always。这三种写回策略依赖文件系统的两个系统调用完成:write和fsync。

write只要把日志记录写到内核缓冲区即可;Redis被广泛使用的一个很重要的原因是它的高性能。因此我们必要要重视所有可能影响Redis性能的因素、机制以及应对方案。影响Redis性能的五大方面的潜在因素,分别是:

Redis内部的阻塞式操作
CPU核和NUMA架构的影响
Redis关键系统配置
Redis内存碎片
Redis缓冲区
在前面的2讲中,学习了会导致Redis变慢的潜在阻塞点以及相应的解决方案,即异步线程机制和CPU绑核。除此之外,还有一些因素会导致Redis变慢。
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这一讲,介绍如何系统性应对Redis变慢这个问题。从问题认定、系统性排查和应对方案这3个方面来讲解。

判断Redis是否变慢?
最直接的方法,查看Redis的响应延迟。通过绝对值来判断,比如执行时间突然增长到几秒。

标签:www,http,Redis,html,DAR,五大,com,book,itangyuan
来源: https://blog.csdn.net/xhsxxf2007/article/details/112597434

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