fix: make the client closeable

Author: tadayosi

src/main/java/com/github/tadayosi/tensorflow/serving/client/TensorFlowServingClient.java

@@ -1,5 +1,6 @@
 package com.github.tadayosi.tensorflow.serving.client;
 
+import java.io.Closeable;
 import java.util.Optional;
 
 import io.grpc.ChannelCredentials;
@@ -14,15 +15,16 @@
 import tensorflow.serving.PredictionServiceGrpc;
 import tensorflow.serving.RegressionOuterClass;
 
-public class TensorFlowServingClient implements TensorFlowServingApi {
+public class TensorFlowServingClient implements TensorFlowServingApi, Closeable {
 
     private static final String DEFAULT_TARGET = "localhost:8500";
 
+    private final ManagedChannel channel;
     private final ModelServiceGrpc.ModelServiceBlockingStub modelService;
     private final PredictionServiceGrpc.PredictionServiceBlockingStub predictionService;
 
     private TensorFlowServingClient(String target, ChannelCredentials credentials) {
-        ManagedChannel channel = Grpc.newChannelBuilder(target, credentials).build();
+        this.channel = Grpc.newChannelBuilder(target, credentials).build();
         this.modelService = ModelServiceGrpc.newBlockingStub(channel);
         this.predictionService = PredictionServiceGrpc.newBlockingStub(channel);
     }
@@ -35,6 +37,11 @@ public static Builder builder() {
         return new Builder();
     }
 
+    @Override
+    public void close() {
+        channel.shutdown();
+    }
+
     @Override
     public GetModelStatus.GetModelStatusResponse getModelStatus(GetModelStatus.GetModelStatusRequest request) {
         return modelService.getModelStatus(request);

src/test/java/com/github/tadayosi/tensorflow/serving/client/ConfigurationTest.java

@@ -24,11 +24,9 @@ void testLoad() {
     @SuppressWarnings("OptionalGetWithoutIsPresent")
     void testSystemProperties() {
         System.setProperty("tfsc4j.target", "dns:///test.com:8501");
-        System.setProperty("tfsc4j.credentials", "aaaaa");
 
         var config = Configuration.load();
 
         assertEquals("dns:///test.com:8501", config.getTarget().get());
-        assertEquals("aaaaa", config.getCredentials().get());
     }
 }

src/test/java/com/github/tadayosi/tensorflow/serving/client/TensorFlowServingTestSupport.java

@@ -1,5 +1,6 @@
 package com.github.tadayosi.tensorflow.serving.client;
 
+import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.containers.wait.strategy.Wait;
@@ -29,4 +30,9 @@ void setUp() {
             .target("localhost:" + tensorflowServing.getMappedPort(8500))
             .build();
     }
+
+    @AfterEach
+    void tearDown() {
+        client.close();
+    }
 }