add user loadbalance extension

workspace-gateway/src/main/java/com/aliware/tianchi/UserLoadBalance.java

+package com.aliware.tianchi;
+
+import org.apache.dubbo.common.URL;
+import org.apache.dubbo.rpc.Invocation;
+import org.apache.dubbo.rpc.Invoker;
+import org.apache.dubbo.rpc.RpcException;
+import org.apache.dubbo.rpc.cluster.LoadBalance;
+
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+
+/**
+ * @author daofeng.xjf
+ */
+public class UserLoadBalance implements LoadBalance {
+
+    @Override
+    public <T> Invoker<T> select(List<Invoker<T>> invokers, URL url, Invocation invocation) throws RpcException {
+        System.out.println("use user loadbalance");
+        return invokers.get(ThreadLocalRandom.current().nextInt(invokers.size()));
+    }
+}

workspace-gateway/src/main/resources/META-INF/services/org.apache.dubbo.rpc.cluster.LoadBalance

+com.aliware.tianchi.UserLoadBalance
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