Can you explain what Netpoller is and how it works in network applications?

Netpoller is a mechanism in network applications that allows efficient monitoring of multiple network connections and input-output events without constantly polling each connection.

It is based on system calls such as epoll (Linux), kqueue (BSD), or IOCP (Windows), which notify the application when sockets are ready for reading or writing.

In Go, netpoller is used within the runtime to implement non-blocking input-output and manage a large number of network connections using goroutines. This enables the creation of high-performance network servers that scale without creating a separate thread for each connection.

It works roughly as follows:

• The application registers sockets with the netpoller.
• The netpoller waits for readiness events.
• When an event occurs, the netpoller notifies the runtime, which wakes up the corresponding goroutine to handle it.

Thus, the netpoller provides efficient multiplexing of network events.