MySQL的監控方式也有很多種：
慢查詢日誌slow_log
優點：MySQL自帶，記錄的慢SQL語句完整；
缺點：需要登錄mysql服務器；如果slow_log文件太大，還需要利用其他工具分析日誌，比如mysqldumpslow；
performance_shema
優點：MySQL自帶，只要有查詢權限即可；
缺點：記錄的SQL語句可能不完整（SQL語句過長，依稀記得是這樣）
授權語句：grant select on performance_schema.* to 'test'@'%';常用查詢語句：
****查詢平均響應時間最多****
SELECT AVG_TIMER_WAIT/1000000000000 as AVG_TIMER_WAIT_S,essbd.*
FROM performance_schema.events_statements_summary_by_digest essbd
ORDER BY AVG_TIMER_WAIT DESC limit 100;
****查詢行讀最多****
SELECT SUM_ROWS_EXAMINED/COUNT_STAR as AVG_ROWS_EXAMINED,essbd.*
FROM performance_schema.events_statements_summary_by_digest essbd
ORDER BY SUM_ROWS_EXAMINED/COUNT_STAR DESC limit 100;
**** 查詢執行次數最多 ****
SELECT *
FROM performance_schema.events_statements_summary_by_digest
ORDER BY COUNT_STAR DESC limit 100;
**** 查詢排序次數最多 ****
SELECT SUM_SORT_ROWS/COUNT_STAR as AVG_SORT_ROWS,essbd.*
FROM performance_schema.events_statements_summary_by_digest essbd
ORDER BY SUM_SORT_ROWS/COUNT_STAR DESC limit 100;
**** 查詢返回結果集最多 ****
SELECT SUM_ROWS_SENT/COUNT_STAR as AVG_ROWS_SENT, essbd.*
FROM performance_schema.events_statements_summary_by_digest essbd
ORDER BY SUM_ROWS_SENT/COUNT_STAR DESC limit 100;
**** 查詢是否無索引 ****
SELECT SUM_NO_INDEX_USED/COUNT_STAR as AVG_NO_INDEX_USED, essbd.*
FROM performance_schema.events_statements_summary_by_digest essbd
ORDER BY SUM_NO_INDEX_USED/COUNT_STAR DESC limit 100;
**** 查詢鎖定時間最多 ****
SELECT SUM_LOCK_TIME/COUNT_STAR/1000000000000 as AVG_LOCK_TIME, essbd.*
FROM performance_schema.events_statements_summary_by_digest essbd
ORDER BY SUM_LOCK_TIME/COUNT_STAR DESC limit 100;
**** 查詢IO最多 ****
SELECT AVG_TIMER_READ/1000000000000 as AVG_TIMER_READ_S,
AVG_TIMER_FETCH /1000000000000 as AVG_TIMER_FETCH_S,tiwsbtt.*
FROM performance_schema.table_io_waits_summary_by_table tiwsbtt
order by AVG_TIMER_READ desc limit 100;druid monitor
如果服務端是用的druid連接池，那麼可以配置druid monitor來進行監控。
優點：從應用層直接進行監控，還可以看到連接池的使用情況；
缺點：需要額外配置druid monitor，如果是微服務框架，貌似每個服務都需要獨立去查看監控數據；