diff --git a/oap-server/exporter/src/main/java/org/apache/skywalking/oap/server/exporter/provider/grpc/GRPCExporter.java b/oap-server/exporter/src/main/java/org/apache/skywalking/oap/server/exporter/provider/grpc/GRPCExporter.java
index 53fc7e99535981369596ee9a66435c30233673ea..fd6d28e65c8e1f8f1f65fef4d983117292619814 100644
--- a/oap-server/exporter/src/main/java/org/apache/skywalking/oap/server/exporter/provider/grpc/GRPCExporter.java
+++ b/oap-server/exporter/src/main/java/org/apache/skywalking/oap/server/exporter/provider/grpc/GRPCExporter.java
@@ -104,8 +104,8 @@ public class GRPCExporter extends MetricFormatter implements MetricValuesExportS
     public void fetchSubscriptionList() {
         final long currentTimeMillis = System.currentTimeMillis();
         if (currentTimeMillis - lastFetchTimestamp > FETCH_SUBSCRIPTION_PERIOD) {
+            fetchListLock.lock();
             try {
-                fetchListLock.lock();
                 if (currentTimeMillis - lastFetchTimestamp > FETCH_SUBSCRIPTION_PERIOD) {
                     lastFetchTimestamp = currentTimeMillis;
                     SubscriptionsResp subscription = blockingStub.withDeadlineAfter(10, TimeUnit.SECONDS)