[Reading Notes] A preliminary exploration of nginx architecture 1_Process model

Original text: http://tengine.taobao.org/book/chapter_02.html%20ngx

After nginx is started, the process background contains a master process and multiple worker processes.
(Terminal nginx command interacts with master)

The master process is used to manage the worker process, including

• receiving signals from the outside world
• sending signals to each worker process
• monitoring the running status of the worker process
• when the worker process exits ( Under abnormal circumstances), a new worker process will be automatically restarted

Basic network events are handled in the worker process. Multiple worker processes are peer-to-peer. They compete equally for requests from clients, and each process is independent of each other. A request can only be processed in one worker process, and a worker process cannot process requests from other processes.

Processing process

1. Each worker process is forked from the master process. In the master process, first establish the socket (listenfd) that needs to be listened, and then fork out multiple worker processes
2. All worker processes listenfd will become readable when a new connection arrives. To ensure that only one process handles the connection, all worker processes grab accept_mutex before registering the listenfd read event
3. The process that grabs the mutex lock registers the listenfd read event. In the read event Call accept to accept the connection. After a worker process accepts the connection, it starts to read the request, parse the request, process the request, generate data, and then return it to the client, and finally disconnect the connection

Benefits of this process model

• For each worker process, it is an independent process and does not need to be locked, so the overhead caused by locks is saved.
• It will also be much more convenient when programming and problem finding.
• Using independent processes can make They will not affect each other. After one process exits, other processes are still working and the service will not be interrupted. The master process will quickly start a new worker process

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