Endpoint port validation in GrpcTransport

core/src/main/java/tech/ydb/core/impl/YdbTransportImpl.java

@@ -126,6 +126,11 @@ static EndpointRecord getDiscoveryEndpoint(GrpcTransportBuilder builder) {
                     + "endpoint " + builder.getEndpoint() + " and empty host " + builder.getHost());
         }
 
+        if (endpointURI.getPort() < 0) {
+            throw new IllegalArgumentException("Can't create discovery rpc, port is not specified for "
+                    + "endpoint " + builder.getEndpoint());
+        }
+
         return new EndpointRecord(endpointURI.getHost(), endpointURI.getPort());
     }
 

core/src/test/java/tech/ydb/core/grpc/GrpcTransportTest.java

@@ -0,0 +1,31 @@
+package tech.ydb.core.grpc;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * @author Mikhail Firsov
+ */
+public class GrpcTransportTest {
+
+    @Test
+    public void failFastOnMissingPort() {
+        String endpoint = "127.1.2.3";
+        try {
+            GrpcTransport.forEndpoint(endpoint, "test").build().close();
+            Assert.fail("Exception expected");
+        } catch (IllegalArgumentException e) {
+            Assert.assertEquals("Can't create discovery rpc, port is not specified for endpoint 127.1.2.3", e.getMessage());
+        }
+    }
+
+    @Test
+    public void doNotFailIfEndpointHasPort() {
+        String endpoint = "127.1.2.3:12345";
+        GrpcTransport
+                .forEndpoint(endpoint, "test")
+                .withInitMode(GrpcTransportBuilder.InitMode.ASYNC)
+                .build()
+                .close();
+    }
+}