补充提交，修复unusedServerAddresses的数量小于1的情况，防止unusedServerAddresses.size为0时，连接巡检线程异常。

skywalking-api/pom.xml

@@ -134,4 +134,12 @@
 			</plugin>
 		</plugins>
 	</build>
+	
+	<distributionManagement>
+		<snapshotRepository>
+			<id>company-private-nexus-library-snapshots</id>
+			<name>company-private-nexus-library-snapshots</name>
+			<url>http://10.1.228.199:18081/nexus/content/repositories/snapshots/</url>
+		</snapshotRepository>
+	</distributionManagement>
 </project>

skywalking-api/src/main/java/com/ai/cloud/skywalking/sender/DataSenderFactoryWithBalance.java

@@ -135,7 +135,7 @@ public class DataSenderFactoryWithBalance {
                     }
 
                     // try to fill up senders. if size is not enough.
-                    while (usingDataSender.size() < maxKeepConnectingSenderSize) {
+                    while (unusedServerAddresses.size() > 0 && usingDataSender.size() < maxKeepConnectingSenderSize) {
                         if ((newSender = findReadySender()) == null) {
                             // no available sender. ignore.
                             break;
@@ -145,7 +145,7 @@ public class DataSenderFactoryWithBalance {
                     }
 
                     // try to switch.
-                    if (sleepTime >= SWITCH_SENDER_INTERVAL) {
+                    if (sleepTime >= SWITCH_SENDER_INTERVAL && unusedServerAddresses.size() > 0) {
                         // if sender is enough, go to switch for balancing.
                         if (usingDataSender.size() >= maxKeepConnectingSenderSize) {
                             DataSender toBeSwitchSender;