A troubleshooting of website crash due to high CPU

problem ： The website has been circling and can't be accessed

screening ：

1： Log in to alicloud to view the server status , According to the normal 【 Running 】
2： View Alibaba cloud servers 【 Monitoring information 】 Show cpu The usage rate is as high as 60%
3：Xshell Connect to server using 【top】 Command view cpu Usage display 【mysql Occupy cpu the height is 280%】
4： Use navicat Connect to the database using 【show full processlist;】 command , List all in progress sql sentence
6： Through analysis, it is found that there are a large number of slow statements with long execution time

Conclusion ：

1：sql The statement execution is too slow and needs to be optimized
2： The size of the temporary table is too low and needs to be reallocated

Emergency treatment ：

Use mysql【kill id;】 The command kills the executing thread

Final treatment ：

1： Re optimize statements , Remove useless linked tables , Precise query conditions
2： Optimize database configuration etc/my.cnf【 There is no need to restart after modification 】
The size of the temporary watch ：【tmp_table_size=200M】
Maximum upper limit of temporary table ：【max_heap_table_size=200M】
join Join table query cache performance ：【join_buffer_size=8M】

mysql Query result annotation ：

Id： Connect mysql Server threads id, Can pass kill Kill the thread .

User： Database user connected to the current thread

Host： The user who executed the statement IP

db: Threaded database , If not, it is null

Command: Displays the command executed by the current connection , It's usually dormant or idle （sleep）, Inquire about （query）, Connect （connect）

Time: When the thread is in its current state , The unit is seconds

State： Shows the... Using the current connection sql The state of the statement

Info: thread-executed sql sentence （ For analysis and troubleshooting sql sentence ）, If there is no statement execution null.