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什么是慢查询
和mysql的慢SQL日志分析一样,redis也有类似的功能,来帮助定位一些慢查询操作。
Redis slowlog是Redis用来记录查询执行时间的日志系统。
查询执行时间指的是不包括像客户端响应(talking)、发送回复等IO操作,而单单是执行一个查询命令所耗费的时间。
另外,slow log保存在内存里面,读写速度非常快,因此你可以放心地使用它,不必担心因为开启slow log而损害Redis的速度。
慢查询参数
首先来关注下慢日志分析对应的两个参数:
1、slowlog-log-slower-than:预设阀值,即记录超过多少时间的记录,默认为10000微秒,即10毫秒。
2、slowlog-max-len:记录慢查询的条数,默认为128条,当超过设置的条数时最早进入队列的将被移除。线上建议增大数值,如:1000,这样可减少队列移除的频率。
127.0.0.1:6379> config get slowlog-log-slower-than1) "slowlog-log-slower-than"2) "10000"127.0.0.1:6379> config get slowlog-max-len1) "slowlog-max-len"2) "128"
可以用config set对这两个参数进行调整,或者在配置文件中设置。
################################## SLOW LOG #################################### The Redis Slow Log is a system to log queries that exceeded a specified# execution time. The execution time does not include the I/O operations# like talking with the client, sending the reply and so forth,# but just the time needed to actually execute the command (this is the only# stage of command execution where the thread is blocked and can not serve# other requests in the meantime).## You can configure the slow log with two parameters: one tells Redis# what is the execution time, in microseconds, to exceed in order for the# command to get logged, and the other parameter is the length of the# slow log. When a new command is logged the oldest one is removed from the# queue of logged commands.# The following time is expressed in microseconds, so 1000000 is equivalent# to one second. Note that a negative number disables the slow log, while# a value of zero forces the logging of every command.slowlog-log-slower-than 10000# There is no limit to this length. Just be aware that it will consume memory.# You can reclaim memory used by the slow log with SLOWLOG RESET.slowlog-max-len 128
慢查询命令
语法:slowlog subcommand [argument]
如,进行查询慢查询、获取慢查询记录的数量、重置慢查询日志等操作:
192.168.10.38:9001> slowlog get(empty list or set)192.168.10.38:9001> slowlog get 10(empty list or set)192.168.10.38:9001> slowlog len (integer) 0192.168.10.38:9001> slowlog resetOK
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