Close HTTP client owned by MinioClient

MinioClient builder and MinioAsyncClient builder allocate a new
OkHttpClient instance. OkHttpClient manages internal resources such as
dispatcher thread pool for executing HTTP requests and should be closed
to dispose of these resources.

api/src/main/java/io/minio/MinioAsyncClient.java

@@ -139,7 +139,8 @@ private MinioAsyncClient(
       boolean useVirtualStyle,
       String region,
       Provider provider,
-      OkHttpClient httpClient) {
+      OkHttpClient httpClient,
+      boolean closeHttpClient) {
     super(
         baseUrl,
         awsS3Prefix,
@@ -148,7 +149,8 @@ private MinioAsyncClient(
         useVirtualStyle,
         region,
         provider,
-        httpClient);
+        httpClient,
+        closeHttpClient);
   }
 
   protected MinioAsyncClient(MinioAsyncClient client) {
@@ -3338,10 +3340,12 @@ public MinioAsyncClient build() {
             "Region missing in Amazon S3 China endpoint " + this.baseUrl);
       }
 
+      boolean closeHttpClient = false;
       if (this.httpClient == null) {
         this.httpClient =
             HttpUtils.newDefaultHttpClient(
                 DEFAULT_CONNECTION_TIMEOUT, DEFAULT_CONNECTION_TIMEOUT, DEFAULT_CONNECTION_TIMEOUT);
+        closeHttpClient = true;
       }
 
       return new MinioAsyncClient(
@@ -3352,7 +3356,8 @@ public MinioAsyncClient build() {
           useVirtualStyle,
           region,
           provider,
-          httpClient);
+          httpClient,
+          closeHttpClient);
     }
   }
 }

api/src/main/java/io/minio/MinioClient.java

@@ -95,7 +95,7 @@
  *         .build();
  * }</pre>
  */
-public class MinioClient {
+public class MinioClient implements AutoCloseable {
   private MinioAsyncClient asyncClient = null;
 
   private MinioClient(MinioAsyncClient asyncClient) {
@@ -2450,6 +2450,13 @@ public void setAwsS3Prefix(String awsS3Prefix) {
     asyncClient.setAwsS3Prefix(awsS3Prefix);
   }
 
+  @Override
+  public void close() throws Exception {
+    if (asyncClient != null) {
+      asyncClient.close();
+    }
+  }
+
   public static Builder builder() {
     return new Builder();
   }

api/src/main/java/io/minio/S3Base.java

@@ -99,7 +99,7 @@
 import okhttp3.ResponseBody;
 
 /** Core S3 API client. */
-public abstract class S3Base {
+public abstract class S3Base implements AutoCloseable {
   static {
     try {
       RequestBody.create(new byte[] {}, null);
@@ -136,6 +136,7 @@ public abstract class S3Base {
   protected String region;
   protected Provider provider;
   protected OkHttpClient httpClient;
+  protected boolean closeHttpClient;
 
   protected S3Base(
       HttpUrl baseUrl,
@@ -145,7 +146,8 @@ protected S3Base(
       boolean useVirtualStyle,
       String region,
       Provider provider,
-      OkHttpClient httpClient) {
+      OkHttpClient httpClient,
+      boolean closeHttpClient) {
     this.baseUrl = baseUrl;
     this.awsS3Prefix = awsS3Prefix;
     this.awsDomainSuffix = awsDomainSuffix;
@@ -154,6 +156,7 @@ protected S3Base(
     this.region = region;
     this.provider = provider;
     this.httpClient = httpClient;
+    this.closeHttpClient = closeHttpClient;
   }
 
   /** @deprecated This method is no longer supported. */
@@ -182,6 +185,7 @@ protected S3Base(
     this.region = region;
     this.provider = provider;
     this.httpClient = httpClient;
+    this.closeHttpClient = false;
   }
 
   protected S3Base(S3Base client) {
@@ -193,6 +197,7 @@ protected S3Base(S3Base client) {
     this.region = client.region;
     this.provider = client.provider;
     this.httpClient = client.httpClient;
+    this.closeHttpClient = false;
   }
 
   /** Check whether argument is valid or not. */
@@ -3757,4 +3762,12 @@ protected CompletableFuture<UploadPartCopyResponse> uploadPartCopyAsync(
               }
             });
   }
+
+  @Override
+  public void close() throws Exception {
+    if (closeHttpClient) {
+      httpClient.dispatcher().executorService().shutdown();
+      httpClient.connectionPool().evictAll();
+    }
+  }
 }