1 files changed, 138 insertions, 0 deletions
diff --git a/pkg/worker_watcher/stack.go b/pkg/worker_watcher/stack.go
new file mode 100644
index 00000000..55f1f52a
--- /dev/null
+++ b/pkg/worker_watcher/stack.go
@@ -0,0 +1,138 @@
+package worker_watcher //nolint:golint,stylecheck
+import (
+	"context"
+	"runtime"
+	"sync"
+	"time"
+
+	"github.com/spiral/roadrunner/v2/interfaces/worker"
+	"github.com/spiral/roadrunner/v2/internal"
+)
+
+type Stack struct {
+	workers            []worker.BaseProcess
+	mutex              sync.RWMutex
+	destroy            bool
+	actualNumOfWorkers int64
+}
+
+func NewWorkersStack() *Stack {
+	w := runtime.NumCPU()
+	return &Stack{
+		workers:            make([]worker.BaseProcess, 0, w),
+		actualNumOfWorkers: 0,
+	}
+}
+
+func (stack *Stack) Reset() {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+	stack.actualNumOfWorkers = 0
+	stack.workers = nil
+}
+
+// Push worker back to the stack
+// If stack in destroy state, Push will provide 100ms window to unlock the mutex
+func (stack *Stack) Push(w worker.BaseProcess) {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+	stack.actualNumOfWorkers++
+	stack.workers = append(stack.workers, w)
+}
+
+func (stack *Stack) IsEmpty() bool {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+	return len(stack.workers) == 0
+}
+
+func (stack *Stack) Pop() (worker.BaseProcess, bool) {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+
+	// do not release new stack
+	if stack.destroy {
+		return nil, true
+	}
+
+	if len(stack.workers) == 0 {
+		return nil, false
+	}
+
+	// move worker
+	w := stack.workers[len(stack.workers)-1]
+	stack.workers = stack.workers[:len(stack.workers)-1]
+	stack.actualNumOfWorkers--
+	return w, false
+}
+
+func (stack *Stack) FindAndRemoveByPid(pid int64) bool {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+	for i := 0; i < len(stack.workers); i++ {
+		// worker in the stack, reallocating
+		if stack.workers[i].Pid() == pid {
+			stack.workers = append(stack.workers[:i], stack.workers[i+1:]...)
+			stack.actualNumOfWorkers--
+			// worker found and removed
+			return true
+		}
+	}
+	// no worker with such ID
+	return false
+}
+
+// Workers return copy of the workers in the stack
+func (stack *Stack) Workers() []worker.BaseProcess {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+	workersCopy := make([]worker.BaseProcess, 0, 1)
+	// copy
+	for _, v := range stack.workers {
+		workersCopy = append(workersCopy, v)
+	}
+
+	return workersCopy
+}
+
+func (stack *Stack) isDestroying() bool {
+	stack.mutex.Lock()
+	defer stack.mutex.Unlock()
+	return stack.destroy
+}
+
+// we also have to give a chance to pool to Push worker (return it)
+func (stack *Stack) Destroy(ctx context.Context) {
+	stack.mutex.Lock()
+	stack.destroy = true
+	stack.mutex.Unlock()
+
+	tt := time.NewTicker(time.Millisecond * 100)
+	for {
+		select {
+		case <-tt.C:
+			stack.mutex.Lock()
+			// that might be one of the workers is working
+			if len(stack.workers) != int(stack.actualNumOfWorkers) {
+				stack.mutex.Unlock()
+				continue
+			}
+			stack.mutex.Unlock()
+			// unnecessary mutex, but
+			// just to make sure. All stack at this moment are in the stack
+			// Pop operation is blocked, push can't be done, since it's not possible to pop
+			stack.mutex.Lock()
+			for i := 0; i < len(stack.workers); i++ {
+				// set state for the stack in the stack (unused at the moment)
+				stack.workers[i].State().Set(internal.StateDestroyed)
+				// kill the worker
+				_ = stack.workers[i].Kill()
+			}
+			stack.mutex.Unlock()
+			tt.Stop()
+			// clear
+			stack.Reset()
+			return
+		}
+	}
+}