How php manages processes

Process Management-Preventing Processes from Becoming Zombie Processes

After the process is created, how do you manage the child processes?

Using signals to manage child processes, there are generally two situations: (Recommended learning: PHP programming from entry to proficiency)

posix_kill() : This function does not, as the name suggests, operate the child process by sending a signal to the child process. When necessary, you can choose to send a process termination signal to the child process to terminate the child process;

pcntl_waitpid(): Wait for or return the child process status of fork. If the specified child process has exited when this function is called (commonly known as a zombie process), this function will return immediately and release all system resources of the child process. This The process can prevent the child process from becoming a zombie process, causing a waste of system resources;

Orphan process: The parent process hangs up, and the child process is taken over by the init process with pid=1 (wait/waitpid) , until the child process's own life cycle ends and the system reclaims resources and the parent process takes relevant recycling operations

Zombie process:The child process exits, and the parent process does not obtain the child process through wait/waitpid Status, process number occupied by the child process and other resource descriptors still exist, causing harm: for example, the process number is limited, and the process number cannot be released, resulting in that there may be no process number available in the future

**Used in the parent process: pcntl_wait Or the purpose of pcntl_waitpid is to prevent the worker from becoming a zombie process

Function: After using pcntl_wait(), after the child process dies, the parent process will also be stopped**

Finally we pass the picture below Let’s briefly summarize and describe the process of multi-process implementation:

Process Management-Inter-process Communication

Queue: such as Redis , Recommended

socket: Recommended

Pipeline: The implementation is complex, and the pipe (pipe) exists in the form of a file, and there is a hard disk IO performance bottleneck

Signal: The amount of information carried is small , difficult to manage

Process management-switch to daemon process

Use & implement

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