Redis如何分析慢查詢操作？
作者：不羈碼農(nóng)
和mysql的慢SQL日志分析一樣，redis也有類似的功能，來幫助定位一些慢查詢操作。Redis slowlog是Redis用來記錄查詢執(zhí)行時間的日志系統(tǒng)。
什么是慢查詢
和mysql的慢SQL日志分析一樣，redis也有類似的功能，來幫助定位一些慢查詢操作。
Redis slowlog是Redis用來記錄查詢執(zhí)行時間的日志系統(tǒng)。
查詢執(zhí)行時間指的是不包括像客戶端響應(yīng)(talking)、發(fā)送回復(fù)等IO操作，而單單是執(zhí)行一個查詢命令所耗費(fèi)的時間。
另外，slow log保存在內(nèi)存里面，讀寫速度非?？?，因此你可以放心地使用它，不必?fù)?dān)心因?yàn)殚_啟slow log而損害Redis的速度。
慢查詢參數(shù)
首先來關(guān)注下慢日志分析對應(yīng)的兩個參數(shù)：
1、slowlog-log-slower-than：預(yù)設(shè)閥值，即記錄超過多少時間的記錄，默認(rèn)為10000微秒，即10毫秒。
2、slowlog-max-len：記錄慢查詢的條數(shù)，默認(rèn)為128條，當(dāng)超過設(shè)置的條數(shù)時最早進(jìn)入隊(duì)列的將被移除。線上建議增大數(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-than
- 1) "slowlog-log-slower-than"
- 2) "10000"
- 127.0.0.1:6379> config get slowlog-max-len
- 1) "slowlog-max-len"
- 2) "128"
可以用config set對這兩個參數(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
慢查詢命令
語法：slowlog subcommand [argument]
如，進(jìn)行查詢慢查詢、獲取慢查詢記錄的數(shù)量、重置慢查詢?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) 0
- 192.168.10.38:9001> slowlog reset
- OK
責(zé)任編輯：龐桂玉
來源：
Java技術(shù)棧
