什么是慢查詢(xún)
慢查詢(xún)的作用:通過(guò)慢查詢(xún)分析,找到有問(wèn)題的命令進(jìn)行優(yōu)化。
和mysql的慢SQL日志分析一樣,redis也有類(lèi)似的功能,來(lái)幫助定位一些慢查詢(xún)操作。
Redis slowlog是Redis用來(lái)記錄查詢(xún)執(zhí)行時(shí)間的日志系統(tǒng)。
查詢(xún)執(zhí)行時(shí)間指的是不包括像客戶(hù)端響應(yīng)(talking)、發(fā)送回復(fù)等IO操作,而單單是執(zhí)行一個(gè)查詢(xún)命令所耗費(fèi)的時(shí)間。
另外,slow log保存在內(nèi)存里面,讀寫(xiě)速度非常快,因此你可以放心地使用它,不必?fù)?dān)心因?yàn)殚_(kāi)啟slow log而損害Redis的速度。
慢查詢(xún)?nèi)罩舅膫€(gè)屬性:
1、第一個(gè)字段是每個(gè)慢查詢(xún)唯一標(biāo)識(shí)。
2、處理完命令后的時(shí)間戳
3、執(zhí)行改名了所需要的時(shí)間,單位微妙
4、命令的參數(shù)列表,是個(gè)數(shù)組類(lèi)型
每個(gè)慢查詢(xún)實(shí)體的ID都是唯一的,而且不會(huì)被重新設(shè)置,只會(huì)在redis重啟后才會(huì)重置它.
慢查詢(xún)參數(shù)
首先來(lái)關(guān)注下慢日志分析對(duì)應(yīng)的兩個(gè)參數(shù):
1、slowlog-log-slower-than:預(yù)設(shè)閥值,即記錄超過(guò)多少時(shí)間的記錄,默認(rèn)為10000微秒,即10毫秒。
2、slowlog-max-len:記錄慢查詢(xún)的條數(shù),默認(rèn)為128條,當(dāng)超過(guò)設(shè)置的條數(shù)時(shí)最早進(jìn)入隊(duì)列的將被移除。線(xiàn)上建議增大數(shù)值,如:1000,這樣可減少隊(duì)列移除的頻率。
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對(duì)這兩個(gè)參數(shù)進(jìn)行調(diào)整,或者在配置文件中設(shè)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
慢查詢(xún)命令
語(yǔ)法:slowlog subcommand [argument]
如,進(jìn)行查詢(xún)慢查詢(xún)、獲取慢查詢(xún)記錄的數(shù)量、重置慢查詢(xún)?nèi)罩镜炔僮鳎?/p>
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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