增加当前节点本地定时缓存，修改部分潜在BUG，启动时Mongo或者redis无法正常连接时，进入启动等待

backend/services/local_node/local_node.go

@@ -0,0 +1,72 @@
+package local_node
+
+import (
+	"crawlab/model"
+	"github.com/apex/log"
+	"github.com/cenkalti/backoff/v4"
+	"go.uber.org/atomic"
+	"sync"
+	"time"
+)
+
+var localNode *LocalNode
+var locker atomic.Int32
+var once sync.Once
+
+type LocalNode struct {
+	node *model.Node
+	sync.RWMutex
+}
+
+func (n *LocalNode) load(retry bool) (err error) {
+	n.Lock()
+	defer n.Unlock()
+	var node model.Node
+	if retry {
+		b := backoff.NewConstantBackOff(1 * time.Second)
+		err = backoff.Retry(func() error {
+			node, err = model.GetCurrentNode()
+			if err != nil {
+				log.WithError(err).Warnf("Get current node info from database failed.  Will after %f seconds, try again.", b.NextBackOff().Seconds())
+			}
+			return err
+		}, b)
+	} else {
+		node, err = model.GetCurrentNode()
+	}
+
+	if err != nil {
+		return
+	}
+	n.node = &node
+	return nil
+}
+func (n *LocalNode) watch() {
+	timer := time.NewTicker(time.Second * 5)
+	for range timer.C {
+		if locker.CAS(0, 1) {
+
+			err := n.load(false)
+
+			if err != nil {
+				log.WithError(err).Errorf("load current node from database failed,")
+			}
+			locker.Store(0)
+		}
+		continue
+	}
+}
+
+func (n *LocalNode) Current() *model.Node {
+	n.RLock()
+	defer n.RUnlock()
+	return n.node
+}
+func CurrentNode() *model.Node {
+	once.Do(func() {
+		localNode = &LocalNode{}
+		_ = localNode.load(true)
+		go localNode.watch()
+	})
+	return localNode.Current()
+}