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Why Is Architecture Important?

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The fundamental basis of any Unix application is the thread or process. (From the Linux OS perspective, threads and processes are mostly identical; the major difference is the degree to which they share memory.) A thread or process is a self‑contained set of instructions that the operating system can schedule to run on a CPU core. Most complex applications run multiple threads or processes in parallel for two reasons:

• They can use more compute cores at the same time.
• Threads and processes make it very easy to do operations in parallel (for example, to handle multiple connections at the same time).

Processes and threads consume resources. They each use memory and other OS resources, and they need to be swapped on and off the cores (an operation called a context switch). Most modern servers can handle hundreds of small, active threads or processes simultaneously, but performance degrades seriously once memory is exhausted or when high I/O load causes a large volume of context switches.

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Setting the Scene – The NGINX Process Model

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Master Process (root user)

To better understand this design, you need to understand how NGINX runs. NGINX has a master process (which performs the privileged operations such as reading configuration and binding to ports) and a number of worker and helper processes.

• Only master runs with root privileges.
• Spawns unprivileged children (worker, cache processes).

• Reads and parses nginx.conf
• Loads dynamic modules and manages sockets.
• Starts worker processes