Three little-known modes of FPM

We often use php-fpm, but not everyone knows that fpm has three modes. Today Xiaonian will take you to understand the three modes of fpm. You can refer to it if you need it.

; Choose how the process manager will control the number of child processes.
; Possible Values:
;   static  - a fixed number (pm.max_children) of child processes;
;   dynamic - the number of child processes are set dynamically based on the
;             following directives. With this process management, there will be
;             always at least 1 children.
;             pm.max_children      - the maximum number of children that can
;                                    be alive at the same time.
;             pm.start_servers     - the number of children created on startup.
;             pm.min_spare_servers - the minimum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is less than this
;                                    number then some children will be created.
;             pm.max_spare_servers - the maximum number of children in 'idle'
;                                    state (waiting to process). If the number
;                                    of 'idle' processes is greater than this
;                                    number then some children will be killed.
;  ondemand - no children are created at startup. Children will be forked when
;             new requests will connect. The following parameter are used:
;             pm.max_children           - the maximum number of children that
;                                         can be alive at the same time.
;             pm.process_idle_timeout   - The number of seconds after which
;                                         an idle process will be killed.
; Note: This value is mandatory.

pm has three modes: static, dynamic and ondemand

static

This method is relatively simple , at startup, the master forks out a corresponding number of worker processes according to the pm.max_children configuration, that is, the number of worker processes is fixed.

dynamic

Dynamic process management, first initialize a certain number of workers according to pm.start_servers when fpm starts.

During operation, if the master finds that the number of idle workers is lower than the number of pm.min_spare_servers configured (indicating that there are too many requests and the workers cannot handle them), it will fork the worker process, but the total number of workers cannot exceed pm.max_children.

If the master finds that the number of idle workers exceeds pm.max_spare_servers (indicating that there are too many idle workers), it will kill some workers to avoid taking up too many resources. The master controls the number of workers through these 4 values. .

ondemand

This method is generally rarely used. The worker process is not allocated at startup, and the master process is notified to fork the worker process after there is a request. The total number of workers does not exceed pm. max_children, the worker process will not exit immediately after the processing is completed, and will exit after the idle time exceeds pm.process_idle_timeout.

pm.max_children: The number of php-fpm processes opened in static mode.

pm.start_servers: The number of starting php-fpm processes in dynamic mode.

pm.min_spare_servers: The minimum number of php-fpm processes in dynamic mode.

pm.max_spare_servers: The maximum number of php-fpm processes in dynamic mode.

FPM’s signal processing

php-fpm reload

php-fpm stop

kill SIGUSR1 php-fpm Reuse the new file and complete the log cutting

kill SIGUSR2 php-fpm Restart the work process and reload the configuration file

Q1: After starting the php-fpm process and killing the php-fpm master process number, can the service continue? A: No (all php-fpm processes are shut down)

Q2: After starting the php-fpm process, kill -9 php-fpm master process number, can the service continue? A: Yes (only the master process is killed, the work process is still working)

Q2: After starting the php-fpm process, kill the php-fpm work process number, can the service continue? A: Yes (after the work process is killed, a new work process is started)

Life cycle of FPM

php_module_startup()

fcgi_accept_request()

php_request_startup()

fmp_request_executing()

php_execute_script ()

fpm_requset_end()

php_request_shutdown()

Because fpm is a resident process, so in php_request_shutdown()Then the cycle will start from fcgi_accept_request().

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