add docker specific columns to server table

local/utl/network/port_pool.go

@@ -0,0 +1,72 @@
+package network
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"strconv"
+	"sync"
+
+	"gorm.io/gorm"
+)
+
+const (
+	defaultPortPoolMin = 9600
+	defaultPortPoolMax = 9700
+)
+
+type PortPoolManager struct {
+	mu    sync.Mutex
+	min   int
+	max   int
+	inUse map[int]struct{}
+}
+
+func NewPortPoolManager(db *gorm.DB) (*PortPoolManager, error) {
+	min := portEnvInt("PORT_POOL_MIN", defaultPortPoolMin)
+	max := portEnvInt("PORT_POOL_MAX", defaultPortPoolMax)
+
+	var ports []int
+	if err := db.Raw("SELECT port FROM servers WHERE platform = 'docker' AND port > 0").Scan(&ports).Error; err != nil {
+		return nil, fmt.Errorf("failed to seed port pool from database: %v", err)
+	}
+
+	inUse := make(map[int]struct{}, len(ports))
+	for _, p := range ports {
+		inUse[p] = struct{}{}
+	}
+
+	return &PortPoolManager{
+		min:   min,
+		max:   max,
+		inUse: inUse,
+	}, nil
+}
+
+func (p *PortPoolManager) Acquire(_ context.Context) (int, error) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	for port := p.min; port <= p.max; port++ {
+		if _, used := p.inUse[port]; !used {
+			p.inUse[port] = struct{}{}
+			return port, nil
+		}
+	}
+	return 0, fmt.Errorf("no available ports in pool [%d-%d]", p.min, p.max)
+}
+
+func (p *PortPoolManager) Release(_ context.Context, port int) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	delete(p.inUse, port)
+}
+
+func portEnvInt(key string, defaultVal int) int {
+	if v := os.Getenv(key); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			return n
+		}
+	}
+	return defaultVal
+}