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One nginx: master process will be started at the same time, and several nginx: worker processes
Nginx will run multiple processes at the same time as needed: A master process (master) and several worker processes (workers). When the cache is configured, there will also be a cache loader process (cache loader) and a cache manager process (cache manager). (Recommended learning:nginx tutorial)
All processes contain only one thread, and inter-process communication is mainly achieved through the "shared memory" mechanism. The main process runs as the root user, while the workers, cache loader and cache manager should all run as unprivileged users.
Through ps –ef | grep nginx, you can see that there are three processes, one master process and two worker processes.
nginx is a multi-process structure. The multi-process structure is designed to ensure the high availability and reliability of nginx, including:
Master Process
Mainly completes the following tasks:
Read and verify configuration information;
Create, Bind and close sockets;
Start, terminate and maintain the number of worker processes;
Reconfigure work characteristics without stopping the service;
Control non-interruption Program upgrade, enable new binary programs and roll back to old versions when needed;
Reopen log files to achieve log rolling;
Compile embedded perl script;
Worker Process
Receives, incoming and processes connections from clients;
Provides reverse proxy and filtering functions;
Any other tasks that nginx can complete;
Cache index reconstruction and process management (Cache Loader & Cache Manager)
Cache module, mainly composed of cache index reconstruction (Cache Loader ) and cache index management (Cache Manager) two types of processes complete the work. The cache index reconstruction process is generated by the main process after the Nginx service is started for a period of time (default is 1 minute), and will automatically exit after the cache metadata reconstruction is completed; the cache index management process generally exists throughout the life cycle of the main process and is responsible for Cache index management.
The main tasks completed by the cache loader process include:
Check cache objects in cache storage;
Use cache metadata to establish an in-memory database;
cache The main tasks of the manager process:
Cache invalidation and expiration check;
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