fix bug (#1633)

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/utils/EnterpriseWeChatUtils.java
      https://sonarcloud.io/project/issues?id=apache-dolphinscheduler&issues=AW9PvkP_YzPBRjkobY7y&open=AW9PvkP_YzPBRjkobY7y
      https://sonarcloud.io/project/issues?id=apache-dolphinscheduler&issues=AW9PvkP_YzPBRjkobY7z&open=AW9PvkP_YzPBRjkobY7z

    dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/AlertServer.java
      https://sonarcloud.io/project/issues?id=apache-dolphinscheduler&issues=AW9PvkRwYzPBRjkobY87&open=AW9PvkRwYzPBRjkobY87

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/AlertServer.java

@@ -39,20 +39,16 @@ public class AlertServer {
 
     private AlertSender alertSender;
 
-    private static volatile AlertServer instance;
+    private static AlertServer instance;
 
     public AlertServer() {
 
     }
 
-    public static AlertServer getInstance(){
+    public synchronized static AlertServer getInstance(){
-        if (null == instance) {
-            synchronized (AlertServer.class) {
         if (null == instance) {
             instance = new AlertServer();
         }
-            }
-        }
         return instance;
     }
 
@@ -63,6 +59,7 @@ public class AlertServer {
                 Thread.sleep(Constants.ALERT_SCAN_INTERVEL);
             } catch (InterruptedException e) {
                 logger.error(e.getMessage(),e);
+                Thread.currentThread().interrupt();
             }
             List<Alert> alerts = alertDao.listWaitExecutionAlert();
             alertSender = new AlertSender(alerts, alertDao);

dolphinscheduler-alert/src/main/java/org/apache/dolphinscheduler/alert/utils/EnterpriseWeChatUtils.java

@@ -86,6 +86,7 @@ public class EnterpriseWeChatUtils {
         String resp;
 
         CloseableHttpClient httpClient = HttpClients.createDefault();
+        try {
             HttpGet httpGet = new HttpGet(enterpriseWeChatTokenUrlReplace);
             CloseableHttpResponse response = httpClient.execute(httpGet);
             try {
@@ -100,6 +101,9 @@ public class EnterpriseWeChatUtils {
                     new TypeToken<Map<String, Object>>() {
                     }.getType());
             return map.get("access_token").toString();
+        } finally {
+            httpClient.close();
+        }
     }
 
     /**
@@ -167,10 +171,11 @@ public class EnterpriseWeChatUtils {
     public static String sendEnterpriseWeChat(String charset, String data, String token) throws IOException {
         String enterpriseWeChatPushUrlReplace = enterpriseWeChatPushUrl.replaceAll("\\$token", token);
 
-        CloseableHttpClient httpclient = HttpClients.createDefault();
+        CloseableHttpClient httpClient = HttpClients.createDefault();
+        try {
             HttpPost httpPost = new HttpPost(enterpriseWeChatPushUrlReplace);
             httpPost.setEntity(new StringEntity(data, charset));
-        CloseableHttpResponse response = httpclient.execute(httpPost);
+            CloseableHttpResponse response = httpClient.execute(httpPost);
             String resp;
             try {
                 HttpEntity entity = response.getEntity();
@@ -179,8 +184,12 @@ public class EnterpriseWeChatUtils {
             } finally {
                 response.close();
             }
-        logger.info("Enterprise WeChat send [{}], param:{}, resp:{}", enterpriseWeChatPushUrl, data, resp);
+            logger.info("Enterprise WeChat send [{}], param:{}, resp:{}", 
+                enterpriseWeChatPushUrl, data, resp);
             return resp;
+        } finally {
+            httpClient.close();
+        }
     }
 
     /**