fix: ensure OkHttp threads are daemon to allow clean JVM shutdown

src/main/java/com/tencentcloudapi/common/http/HttpConnection.java

@@ -19,12 +19,15 @@
 
 import com.tencentcloudapi.common.exception.TencentCloudSDKException;
 import okhttp3.*;
+import okhttp3.internal.Util;
 
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLSocketFactory;
 import javax.net.ssl.X509TrustManager;
 import java.io.IOException;
 import java.net.Proxy;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
 public class HttpConnection {
@@ -33,7 +36,7 @@ public class HttpConnection {
     // https://github.com/square/okhttp/issues/3372
     // Creating dispatcher and connectionPool is expensive.
     // Share them between OkHttpClients by singleton's Builder.
-    private static final OkHttpClient clientSingleton = new OkHttpClient();
+    private static final OkHttpClient clientSingleton = newOkhttpClient();
     private OkHttpClient client;
 
     public HttpConnection(Integer connTimeout, Integer readTimeout, Integer writeTimeout) {
@@ -150,4 +153,11 @@ public void setHttpClient(Object httpClient) {
     public Object getHttpClient() {
         return client;
     }
+
+    private static OkHttpClient newOkhttpClient() {
+        ThreadPoolExecutor executor = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60, TimeUnit.SECONDS,
+                new SynchronousQueue<Runnable>(), Util.threadFactory("OkHttp Dispatcher", true));
+        Dispatcher dispatcher = new Dispatcher(executor);
+        return new OkHttpClient.Builder().dispatcher(dispatcher).build();
+    }
 }

src/test/java/com/tencentcloudapi/integration/common/DaemonThreadTest.java

@@ -0,0 +1,33 @@
+package com.tencentcloudapi.integration.common;
+
+import com.tencentcloudapi.common.CommonClient;
+import com.tencentcloudapi.common.Credential;
+import org.junit.Test;
+
+import static org.junit.Assert.fail;
+
+public class DaemonThreadTest {
+
+    @Test
+    // ensure OkHttp threads are daemon to allow clean JVM shutdown
+    public void testOkhttpUseDaemonThread() {
+        Credential cred = new Credential(
+                System.getenv("TENCENTCLOUD_SECRET_ID"),
+                System.getenv("TENCENTCLOUD_SECRET_KEY")
+        );
+        CommonClient client = new CommonClient("cvm", "2017-03-12", cred, "ap-guangzhou");
+        try {
+            client.call(
+                    "DescribeInstances",
+                    "{\"Limit\": 1, \"Filters\":[{\"Name\":\"zone\",\"Values\":[\"ap-guangzhou-1\"]}]}");
+        } catch (Exception e) {
+            fail(e.toString());
+        }
+
+        for (Thread t : Thread.getAllStackTraces().keySet()) {
+            if (t.getName().startsWith("OkHttp") && !t.isDaemon()) {
+                fail("thread should be daemon: " + t.getName());
+            }
+        }
+    }
+}