shm

shm

Accessing system shared memory from Go applications. I use it to share host state (ACTIVE or STANDBY) between SCADA applications running on the same host. This is required for compatibility with legacy modules.

How to use

var hostState unsafe.Pointer
...

// HostState connect to shared memory to retrieve the host state
func HostState() (unsafe.Pointer, error) {
	segment, err := shm.OpenSegment()

	if err != nil {
		return nil, err
	}

	return segment.Attach()
}

// IsCurrentHostStateActive checking current host state. Server sends data only in the active state.
func IsCurrentHostStateActive() bool {
	if hostState == nil {
		return true
	}

	if *(*uint16)(hostState) != 2 {
		return true
	}

	return false
}

...

hostState, err = HostState()
	if err != nil {
		log.Errorf("Failed to get host state shared memory: %v", err)
	}

	if IsCurrentHostStateActive() {
    ...