YARN-4668. Reuse objectMapper instance in Yarn. (Yiqun Lin via gtcarrera9)

(cherry picked from commit 221582c4ab0ff1d5936f754f23da140aac656654)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/client/api/impl/TimelineClientImpl.java

@@ -85,6 +85,7 @@ public class TimelineClientImpl extends TimelineClient {
 
   private static final Log LOG = LogFactory.getLog(TimelineClientImpl.class);
   private static final String RESOURCE_URI_STR = "/ws/v1/timeline/";
+  private static final ObjectMapper MAPPER = new ObjectMapper();
   private static final Joiner JOINER = Joiner.on("");
   public final static int DEFAULT_SOCKET_TIMEOUT = 1 * 60 * 1000; // 1 minute
 
@@ -563,15 +564,14 @@ public class TimelineClientImpl extends TimelineClient {
       LOG.error("File [" + jsonFile.getAbsolutePath() + "] doesn't exist");
       return;
     }
-    ObjectMapper mapper = new ObjectMapper();
-    YarnJacksonJaxbJsonProvider.configObjectMapper(mapper);
+    YarnJacksonJaxbJsonProvider.configObjectMapper(MAPPER);
     TimelineEntities entities = null;
     TimelineDomains domains = null;
     try {
       if (type.equals(ENTITY_DATA_TYPE)) {
-        entities = mapper.readValue(jsonFile, TimelineEntities.class);
+        entities = MAPPER.readValue(jsonFile, TimelineEntities.class);
       } else if (type.equals(DOMAIN_DATA_TYPE)){
-        domains = mapper.readValue(jsonFile, TimelineDomains.class);
+        domains = MAPPER.readValue(jsonFile, TimelineDomains.class);
       }
     } catch (Exception e) {
       LOG.error("Error when reading  " + e.getMessage());