How to Fork a Go Process and Retrieve Its PID?

Forking a Go Process and Retrieving Its ID

Question:

How to fork a Go process and get a new process ID?

Answer:

To fork a Go process and get the ID of the new process, you can use the syscall.ForkExec() function, which is located in the syscall package.

It should be noted that the fork() function in the Go library cannot meet your needs.

When the fork() function was first invented, threads were not used, and the process always had only one execution thread, so forking was safe. However, Go's heavy use of operating system-level threads to drive goroutine scheduling changes the situation fundamentally.

Undecorated fork(2) on Linux now only causes the child process to have a single thread that calls fork(2) in the parent process, while all threads used by the Go runtime (including some critical threads) Not among them. Basically this means that you cannot expect the child process to continue executing Go code, the only thing you can reasonably do is to execute exec(2) immediately. Note that this is what syscall.ForkExec() is supposed to be used for.

Now think about this further. I think the only thing that is useful right now for calling fork(2) directly is a "best effort asynchronous process state snapshot" like the one used by Redis. This technique relies on the fact that the child process inherits all memory data pages of its parent process, but the operating system uses copy-on-write technique without actually copying all the data, so the child process can stop there and save all the data structures to disk while its parent process is modifying data in its own address space. And any other possible use of fork() would mean instant exec(), which is what functions like exec.Command() are for, so why use fork() at all?

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