les: fix issue

les/server_handler.go

@@ -127,25 +127,26 @@ func (h *serverHandler) handle(p *peer) error {
 	}
 	defer p.fcClient.Disconnect()
 
+	// Disconnect the inbound peer if it's rejected by clientPool
+	if !h.server.clientPool.connect(p, 0) {
+		p.Log().Debug("Light Ethereum peer registration failed", "err", errFullClientPool)
+		return errFullClientPool
+	}
 	// Register the peer locally
 	if err := h.server.peers.Register(p); err != nil {
+		h.server.clientPool.disconnect(p)
 		p.Log().Error("Light Ethereum peer registration failed", "err", err)
 		return err
 	}
-	// Disconnect the inbound peer if it's rejected by clientPool
-	if h.server.clientPool.connect(p, 0) {
-		p.Log().Debug("Light Ethereum peer registration failed", "err", errFullClientPool)
-		return errFullClientPool
-	}
 	clientConnectionGauge.Update(int64(h.server.peers.Len()))
 
 	var wg sync.WaitGroup // Wait group used to track all in-flight task routines.
 
 	connectedAt := mclock.Now()
 	defer func() {
 		wg.Wait() // Ensure all background task routines have exited.
-		h.server.clientPool.disconnect(p)
 		h.server.peers.Unregister(p.id)
+		h.server.clientPool.disconnect(p)
 		clientConnectionGauge.Update(int64(h.server.peers.Len()))
 		connectionTimer.Update(time.Duration(mclock.Now() - connectedAt))
 	}()

les/test_helper.go

@@ -281,6 +281,7 @@ func newTestServerHandler(blocks int, indexers []*core.ChainIndexer, db ethdb.Da
 	server.costTracker, server.freeCapacity = newCostTracker(db, server.config)
 	server.costTracker.testCostList = testCostList(0) // Disable flow control mechanism.
 	server.clientPool = newClientPool(db, 1, 10000, clock, nil)
+	server.clientPool.setLimits(10000, 10000) // Assign enough capacity for clientpool
 	server.handler = newServerHandler(server, simulation.Blockchain(), db, txpool, func() bool { return true })
 	if server.oracle != nil {
 		server.oracle.start(simulation)