Common interview questions about swoole

One 、 Why do you use swoole, What pain points in your project can be solved ？

swoole Is a network communication and asynchronous IO The engine of , A basic library ;

swoole Compared with apache/fpm, Major savings PHP The performance overhead of each creation and destruction of framework and global objects , It is a process resident memory type .

Two 、 How did you get through swoole Performance enhancing , How to do it? ？

1. Process resident memory ：

   swoole Itself is a process resident memory , When the process starts PHP The framework and other codes are read and compiled , You don't need to perform the compilation step every time you start , Greatly reduce the running time of the script ;

2. Connection pool

   php-fpm The pattern of php Because all resources are destroyed at the end of each request , Therefore, connection pooling cannot be used ; And based on swoole Process resident memory mode , You can speed up the program through connection pooling ,

   Using connection pooling can reduce the response time of programs , It can also effectively protect back-end resources .

3. Asynchrony can be handled using a coroutine IO

   When you need to request multiple data in development , It takes a long time for each piece of data to be requested separately , The conventional php-fpm It's blocking operation , This type of data processing cannot be accelerated ; And based on swoole The program , This kind of business can be parallelized , Request the data source of the back end in parallel , It can greatly optimize the running time of this kind of business .

3、 ... and 、swoole What is the collaboration process in , How to use it? ？ Why can synergy improve concurrency ？

Cooperative processes are switched through cooperation rather than preemption , It creates and switches resources such as memory, which is much smaller than threads ( It can be understood as smaller threads );

The use of synergy is through Swoole\Coroutine perhaps Co\ Namespace short names simplify class names to create ;

A coroutine can process tasks asynchronously , Support concurrency , And the resource consumption is small .

Four 、 It was used swoole in the future , Will there be a memory leak ？ If something happens, how to solve it ？

swoole Because it is resident memory , Once the resource is loaded, enter , Will always exist in memory . For local variables ,swoole It will be released automatically after the callback function ends ; For global variables (lobal Declared variables ,

static Declared object properties or static variables and super global variables in functions ),swoole It doesn't automatically release ; Therefore, bad operation will lead to memory leakage .

solve ：

• stay onClose Clean up variables in callback ;

• swoole Provides max_request and max_task_request Mechanism : After the process completes the specified number of tasks , Will automatically exit , Achieve the purpose of releasing resources and memory ; Then manager The process will start again worker/task Process to continue processing tasks .

      Usage restriction ：
  
     max_request Can only be used for synchronous blocking 、 Stateless request response server program ;
  
      Pure asynchronous Server Should not be set max_request
  
      Use Base Mode time max_request It's invalid 
  

5、 ... and 、swoole and php-fpm The difference between

PHP-FPM:

Early versions of PHP There's no built-in WEB The server , It provides SAPI(Server API) Connect with the third party . It's very popular now php-fpm It is through FastCGI Agreement to deal with PHP With a third party WEB Communication between servers . such as Nginx + php-fpm The combination of , It works this way fpm yes Master/Worker Pattern , Start a Master Process listening from Nginx Request , Again fork Multiple Worker The process processes the request . Every Worker The process can only handle one request , The life cycle of a single process is roughly as follows ：

1. Initialization module .

2. Initialization request . The request here is a request PHP The meaning of executing code , Is not HTTP Request .

3. perform PHP Script .

4. End request .

5. Close the module .

The multi process model depends on the number of processes to solve the concurrency problem , A process can only handle one connection , When starting a large number of processes , Process scheduling consumption may account for CPU Tens of percent or even 100%, such as C10K problem , The multi process model is not enough .

Swoole:

Swoole The same is true of Master/Worker Pattern , The difference is Master There are multiple processes Reactor Threads ,Master It's just an event generator , Responsible for monitoring Socket Event change of handle .Worker Run as a multiprocess , Receive from Reactor Thread request , And execute the callback function (PHP Compiling ). start-up Master The process flow is roughly ：

1. Initialization module .

2. Initialization request . because swoole Need to pass through cli How to run , So when initializing the request , Will not initialize PHP Global variable of , Such as $_SERVER, $_POST, $_GET etc. .

3. perform PHP Script . Including the lexical 、 Syntax analysis , Variable 、 function 、 Class initialization, etc ,Master Enter monitor state , It doesn't end the process .

Swoole The principle of acceleration

• from Reactor(epoll Of IO Reuse mode ) Responsible for monitoring Socket Event change of handle , Solve the problem of high concurrency .

• Save... By resident memory PHP Code initialization time , When using heavy frames , use swoole The acceleration effect is very obvious .

The contrast is different

PHP-FPM

• Master The main process / Worker Multi process mode .

• start-up Master, adopt FastCGI Protocol listening from Nginx Requests for transmission .

• Every Worker The process corresponds to only one connection , Used to perform complete PHP Code .

• PHP Code execution completed , The occupied memory will be destroyed , The next request requires re initialization and other cumbersome operations .

• Used only for HTTP Server.

Swoole

• Master The main process ( By multiple Reactor Thread composition )/ Worker Multi process ( Or multithreading ) Pattern

• start-up Master, initialization PHP Code , from Reactor monitor Socket Event change of handle .

• Reactor The main thread is responsible for the balance of sub threads ,Manager Process management Worker Multi process , Include TaskWorker The process of .

• Every Worker from Reactor Request , You only need to execute the part of the callback function PHP Code .

• Only in Master Execute once at startup PHP Initialization code ,Master Enter monitor state , It doesn't end the process .

• Not only for HTTP Server, You can also create TCP Connect 、WebSocket Connect .