HttpGet:add http time out

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/remote/DiscoveryRestServiceClient.java

@@ -26,6 +26,7 @@ import java.io.IOException;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Random;
+import org.apache.http.client.config.RequestConfig;
 import org.apache.http.client.methods.CloseableHttpResponse;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.impl.client.CloseableHttpClient;
@@ -46,6 +47,9 @@ import static org.apache.skywalking.apm.agent.core.conf.RemoteDownstreamConfig.C
  */
 public class DiscoveryRestServiceClient implements Runnable {
     private static final ILog logger = LogManager.getLogger(DiscoveryRestServiceClient.class);
+    private static final int HTTP_CONNECT_TIMEOUT = 2000;
+    private static final int HTTP_CONNECTION_REQUEST_TIMEOUT = 1000;
+    private static final int HTTP_SOCKET_TIMEOUT = 2000;
     private String[] serverList;
     private volatile int selectedServer = -1;
 
@@ -133,7 +137,11 @@ public class DiscoveryRestServiceClient implements Runnable {
             return null;
         }
         HttpGet httpGet = new HttpGet("http://" + serverList[selectedServer] + Config.Collector.DISCOVERY_SERVICE_NAME);
-
+        RequestConfig requestConfig = RequestConfig.custom()
+            .setConnectTimeout(HTTP_CONNECT_TIMEOUT)
+            .setConnectionRequestTimeout(HTTP_CONNECTION_REQUEST_TIMEOUT)
+            .setSocketTimeout(HTTP_SOCKET_TIMEOUT).build();
+        httpGet.setConfig(requestConfig);
         return httpGet;
     }