Traditional architecture

NginxDeveloping in + PHP-Fpm mode is very simple without worrying about memory leaks.

phpThe fastcgi Process Manager php-fpm and nginx the mate are already running well enough, but because php-fpm it is itself a synchronous blocking process Model , all resources are released after the request ends, including a series of objects created by THE framework initialization, causing the PHP process to idling (Create a The "_ _ Destruction of the _ _ created) consumes a lot of CPU resources, resulting in limited throughput capacity for a single machine. Request tamping, will result in the CPU inability to release resources, greatly wasted the CPU use rate.

Php-fpm

The PHP-FPM process model is also very simple and belongs to the pre-derived child process pattern You must know that the early Apache was using this pattern to a request on fork a process, the cost of the process is very large. This can significantly reduce throughput, and the number of concurrency is determined by the number of processes.fpm

Pre-derived child process mode

After the program starts, N a process is created. Each child process enters Accept , waiting for the new connection to enter. When a client connects to the server, one of the child processes wakes up, begins processing client requests, and no longer accepts new TCP连接 . When this connection is closed, the child processes are released, re-entered Accept , and participate in the processing of the new connection.

Advantage

The advantage of this model is that it is perfectly possible to reuse processes and does not require much context switching.

Disadvantage

This model relies heavily on the number of processes to solve concurrency problems, a client connection needs to occupy a process, the number of worker processes, and how much concurrent processing power. The number of processes that the operating system can create is limited.

PHP framework initialization consumes a lot of compute resources, and each request needs to be initialized.

Starting a large number of processes can result in additional process scheduling consumption. When hundreds of processes, process context switching scheduling consumption accounts for less than 1% of the CPU is negligible, and if you start thousands of or even tens of thousands of processes, the consumption will rise in a straight line. Scheduling consumption may account for percent or even 100% of the CPU.

If requesting a third-party request is very slow, the request process will always consume CPU resources and waste expensive hardware resources

For example, an instant chat program, a server may have to maintain a hundreds of thousands of connection, then start hundreds of thousands of of the process to hold. It's obviously not possible.

Is there a technology that can handle all concurrency within a process IO ? The answer is yes, this is IO multiplexing technology.

The problem of PHP-FPM working mode

模型

  • nginxBased on epoll the event model, one worker can handle multiple requests at the same time

  • fpm-workerA request can be processed at the same time

  • fpm-workerThe framework needs to be reinitialized before each processing mvc of the request, and then the resource is freed

  • High concurrency requests, fpm-worker insufficient use, nginx direct response 502

  • Large switching consumption between fpm-worker processes

So what other solutions do we have?

We analyze our business. It is not difficult to find that 90% the above business Is IO Intensive Business , we only need to improve THE ability of IO reuse can improve the ability of single- php-fpm machine throughput, in addition to the need to replace synchronous blocking mode with Asynchronous non-blocking mode , asynchronous opening mode is more complex and not easy to maintain, of course php-fpm , it can not be used, it will solve our core problem-performance.

In IO intensive business We need frequent context switching, which is too complex to develop in thread mode.

The number of threads that can be opened in a process is also limited, too many threads will also increase CPU the load and memory resources, threads do not block state , IO blocking can not actively cede CPU resources, belongs to the preemptive scheduling model . Not very suitable for PHP development.

The swoole 4.+ full-collaboration mode is turned on to allow synchronous code to execute asynchronously. For more information, see Why you want to use Swoole

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