解决 无法连接数据库:Lost connection to MySQL server at 'reading initial communication packet', system error: 111

报错现象：

无法连接数据库:Lost connection to MySQL server at 'reading initial communication packet', system error: 111

数据库错误日志：

InnoDB: mmap(274726912 bytes) failed; errno 12

解决方案，调整以下参数：

pm = ondemand

; The number of child processes to be created when pm is set to 'static' and the

; maximum number of child processes to be created when pm is set to 'dynamic'.

; This value sets the limit on the number of simultaneous requests that will be

; served. Equivalent to the ApacheMaxClients directive with mpm_prefork.

; Equivalent to the PHP_FCGI_CHILDREN environment variable in the original PHP

; CGI.

; Note: Used when pm is set to either 'static' or 'dynamic'

; Note: This value is mandatory.

pm.max_children = 100

; The number of requests each child process should execute before respawning.

; This can be useful to work around memory leaks in 3rd party libraries. For

; endless request processing specify '0'. Equivalent to PHP_FCGI_MAX_REQUESTS.

; Default Value: 0

;pm.max_requests = 500

pm.max_requests =5000