Fix child process termination in containerized environments

[Copilot]

Summary

This PR fixes child process termination issues in containerized environments, addressing resource leaks (especially GPU memory) when stopping processes. Fixes mudler/LocalAI#7958.

Changes Implemented

• 1. Add GracefulTimeout (default 15s) and KillProcessGroup (default true) config options
• 2. Add WithGracefulTimeout() and WithKillProcessGroup() option functions
• 3. Create process groups with Setpgid: true in Run() (Unix/Linux)
• 4. Kill entire process group using negative PID in Stop() (Unix/Linux)
• 5. Add graceful timeout: wait between SIGTERM and SIGKILL
• 6. Add SetSubreaper() function for Linux (using prctl)
• 7. Add no-op stub for non-Linux platforms
• 8. Add test verifying child processes are killed when parent stops
• 9. Create platform-specific implementations (Unix vs Windows)
• 10. Actually call SetSubreaper() in Run() and implement child reaping
• 11. Add reapChildren() to wait for and reap orphaned child processes
• 12. Improve error handling in Stop() with proper context and wrapping

Root Causes Addressed

✅ No process group handling → Added Setpgid: true for Unix/Linux
✅ Signals only sent to direct child → Sending to entire process group via negative PID
✅ Immediate SIGKILL after SIGTERM → Added 15-second graceful timeout
✅ No subreaper in containers → Linux-specific subreaper support via prctl + child reaping

Subreaper Implementation

The subreaper functionality now properly:

• Calls SetSubreaper() when starting a process to mark the current process as a subreaper
• Spawns a reapChildren() goroutine that continuously waits for and reaps orphaned child processes
• Prevents zombie processes from accumulating when child processes terminate
• Handles platform differences (Unix vs Windows)

Error Handling Improvements

The Stop() method now provides better error context:

• Wraps errors with fmt.Errorf and %w to preserve error chains
• Includes contextual information (PID values, signal types) in error messages
• Checks and reports errors from killProcess() calls
• Provides specific error messages for different failure scenarios

Testing

• All 6 tests passing (including new process group termination test)
• Builds successfully on Linux, macOS, and Windows
• No race conditions detected
• No security vulnerabilities (CodeQL clean)

Files Changed

• config.go: Added new config fields with defaults
• options.go: Added option functions
• process.go: Updated Run() to call SetSubreaper(), monitor() to spawn reaper, improved Stop() error handling
• process_unix.go: Unix-specific process group handling + reapChildren() implementation
• process_windows.go: Windows-specific process handling + no-op reapChildren()
• subreaper_linux.go: Linux subreaper support
• subreaper_other.go: No-op for non-Linux platforms
• process_test.go: Added process group termination test

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[mudler]

@copilot seems you forgot to actually set the process as subreaper and waiting for its childs

[Copilot]

This has been addressed in commit c1a9ec4. The process is now properly set as a subreaper by calling SetSubreaper() in Run(), and reapChildren() continuously waits for and reaps orphaned child processes using Wait4(-1, ...) with WNOHANG.

[mudler]

@copilot since we are here at touching Stop(), let's improve errors that are returned such as we can identify better where they are coming from, and don't shadow errors, but wrap them where necessary.

[Copilot]

Improved in 2b22273. The Stop() method now:

• Wraps errors with fmt.Errorf and %w to preserve error chains
• Includes contextual information (PID values, signal types) in error messages
• Checks and reports errors from killProcess() calls instead of ignoring them
• Provides specific error messages for each failure scenario (read PID, parse PID, send signal)