HDFS-9768. Reuse ObjectMapper instance in HDFS to improve the performance. Contributed by Lin Yiqun.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/oauth2/ConfRefreshTokenBasedAccessTokenProvider.java

@@ -29,6 +29,7 @@ import org.apache.hadoop.hdfs.web.URLConnectionFactory;
 import org.apache.hadoop.util.Timer;
 import org.apache.http.HttpStatus;
 import org.codehaus.jackson.map.ObjectMapper;
+import org.codehaus.jackson.map.ObjectReader;
 
 import java.io.IOException;
 import java.util.Map;
@@ -54,6 +55,8 @@ import static org.apache.hadoop.hdfs.web.oauth2.Utils.notNull;
 @InterfaceStability.Evolving
 public class ConfRefreshTokenBasedAccessTokenProvider
     extends AccessTokenProvider {
+  private static final ObjectReader READER =
+      new ObjectMapper().reader(Map.class);
 
   public static final String OAUTH_REFRESH_TOKEN_KEY
       = "dfs.webhdfs.oauth2.refresh.token";
@@ -126,10 +129,7 @@ public class ConfRefreshTokenBasedAccessTokenProvider
             + responseBody.code() + ", text = " + responseBody.toString());
       }
 
-      ObjectMapper mapper = new ObjectMapper();
-      Map<?, ?> response = mapper.reader(Map.class)
-          .readValue(responseBody.body().string());
-
+      Map<?, ?> response = READER.readValue(responseBody.body().string());
 
       String newExpiresIn = response.get(EXPIRES_IN).toString();
       accessTokenTimer.setExpiresIn(newExpiresIn);

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/oauth2/CredentialBasedAccessTokenProvider.java

@@ -29,6 +29,7 @@ import org.apache.hadoop.hdfs.web.URLConnectionFactory;
 import org.apache.hadoop.util.Timer;
 import org.apache.http.HttpStatus;
 import org.codehaus.jackson.map.ObjectMapper;
+import org.codehaus.jackson.map.ObjectReader;
 
 import java.io.IOException;
 import java.util.Map;
@@ -54,6 +55,9 @@ import static org.apache.hadoop.hdfs.web.oauth2.Utils.notNull;
 @InterfaceStability.Evolving
 public abstract class CredentialBasedAccessTokenProvider
     extends AccessTokenProvider {
+  private static final ObjectReader READER =
+      new ObjectMapper().reader(Map.class);
+
   public static final String OAUTH_CREDENTIAL_KEY
       = "dfs.webhdfs.oauth2.credential";
 
@@ -119,9 +123,7 @@ public abstract class CredentialBasedAccessTokenProvider
             + responseBody.code() + ", text = " + responseBody.toString());
       }
 
-      ObjectMapper mapper = new ObjectMapper();
-      Map<?, ?> response = mapper.reader(Map.class)
-          .readValue(responseBody.body().string());
+      Map<?, ?> response = READER.readValue(responseBody.body().string());
 
       String newExpiresIn = response.get(EXPIRES_IN).toString();
       timer.setExpiresIn(newExpiresIn);

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -1978,6 +1978,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9686. Remove useless boxing/unboxing code.
     (Kousuke Saruta via aajisaka)
 
+    HDFS-9768. Reuse ObjectMapper instance in HDFS to improve the performance.
+    (Lin Yiqun via aajisaka)
+
   BUG FIXES
 
     HDFS-7501. TransactionsSinceLastCheckpoint can be negative on SBNs.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java

@@ -62,6 +62,8 @@ import org.apache.hadoop.util.Time;
 import org.apache.hadoop.util.Timer;
 import org.codehaus.jackson.annotate.JsonProperty;
 import org.codehaus.jackson.map.ObjectMapper;
+import org.codehaus.jackson.map.ObjectReader;
+import org.codehaus.jackson.map.ObjectWriter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -80,6 +82,10 @@ import com.google.common.util.concurrent.ThreadFactoryBuilder;
 public class FsVolumeImpl implements FsVolumeSpi {
   public static final Logger LOG =
       LoggerFactory.getLogger(FsVolumeImpl.class);
+  private static final ObjectWriter WRITER =
+      new ObjectMapper().writerWithDefaultPrettyPrinter();
+  private static final ObjectReader READER =
+      new ObjectMapper().reader(BlockIteratorState.class);
 
   private final FsDatasetImpl dataset;
   private final String storageID;
@@ -708,10 +714,9 @@ public class FsVolumeImpl implements FsVolumeSpi {
     public void save() throws IOException {
       state.lastSavedMs = Time.now();
       boolean success = false;
-      ObjectMapper mapper = new ObjectMapper();
       try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(
                 new FileOutputStream(getTempSaveFile(), false), "UTF-8"))) {
-        mapper.writerWithDefaultPrettyPrinter().writeValue(writer, state);
+        WRITER.writeValue(writer, state);
         success = true;
       } finally {
         if (!success) {
@@ -725,17 +730,16 @@ public class FsVolumeImpl implements FsVolumeSpi {
           StandardCopyOption.ATOMIC_MOVE);
       if (LOG.isTraceEnabled()) {
         LOG.trace("save({}, {}): saved {}", storageID, bpid,
-            mapper.writerWithDefaultPrettyPrinter().writeValueAsString(state));
+            WRITER.writeValueAsString(state));
       }
     }
 
     public void load() throws IOException {
-      ObjectMapper mapper = new ObjectMapper();
       File file = getSaveFile();
-      this.state = mapper.reader(BlockIteratorState.class).readValue(file);
+      this.state = READER.readValue(file);
       LOG.trace("load({}, {}): loaded iterator {} from {}: {}", storageID,
           bpid, name, file.getAbsoluteFile(),
-          mapper.writerWithDefaultPrettyPrinter().writeValueAsString(state));
+          WRITER.writeValueAsString(state));
     }
 
     File getSaveFile() {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -248,6 +248,7 @@ import org.apache.hadoop.hdfs.server.protocol.NamespaceInfo;
 import org.apache.hadoop.hdfs.server.protocol.StorageReceivedDeletedBlocks;
 import org.apache.hadoop.hdfs.server.protocol.StorageReport;
 import org.apache.hadoop.hdfs.server.protocol.VolumeFailureSummary;
+import org.apache.hadoop.hdfs.web.JsonUtil;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.ipc.CallerContext;
@@ -275,7 +276,6 @@ import org.apache.hadoop.util.VersionInfo;
 import org.apache.log4j.Appender;
 import org.apache.log4j.AsyncAppender;
 import org.apache.log4j.Logger;
-import org.codehaus.jackson.map.ObjectMapper;
 import org.mortbay.util.ajax.JSON;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -4557,9 +4557,8 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     Map<String, Object> topMap = new TreeMap<String, Object>();
     topMap.put("windows", topWindows);
     topMap.put("timestamp", DFSUtil.dateToIso8601String(now));
-    ObjectMapper mapper = new ObjectMapper();
     try {
-      return mapper.writeValueAsString(topMap);
+      return JsonUtil.toJsonString(topMap);
     } catch (IOException e) {
       LOG.warn("Failed to fetch TopUser metrics", e);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/FSImageLoader.java

@@ -54,7 +54,6 @@ import org.apache.hadoop.hdfs.web.JsonUtil;
 import org.apache.hadoop.hdfs.web.resources.XAttrEncodingParam;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.util.LimitInputStream;
-import org.codehaus.jackson.map.ObjectMapper;
 
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
@@ -263,10 +262,9 @@ class FSImageLoader {
    * @throws IOException if failed to serialize fileStatus to JSON.
    */
   String getFileStatus(String path) throws IOException {
-    ObjectMapper mapper = new ObjectMapper();
     FsImageProto.INodeSection.INode inode = fromINodeId(lookup(path));
     return "{\"FileStatus\":\n"
-        + mapper.writeValueAsString(getFileStatus(inode, false)) + "\n}\n";
+        + JsonUtil.toJsonString(getFileStatus(inode, false)) + "\n}\n";
   }
 
   /**
@@ -277,7 +275,6 @@ class FSImageLoader {
    */
   String listStatus(String path) throws IOException {
     StringBuilder sb = new StringBuilder();
-    ObjectMapper mapper = new ObjectMapper();
     List<Map<String, Object>> fileStatusList = getFileStatusList(path);
     sb.append("{\"FileStatuses\":{\"FileStatus\":[\n");
     int i = 0;
@@ -285,7 +282,7 @@ class FSImageLoader {
       if (i++ != 0) {
         sb.append(',');
       }
-      sb.append(mapper.writeValueAsString(fileStatusMap));
+      sb.append(JsonUtil.toJsonString(fileStatusMap));
     }
     sb.append("\n]}}\n");
     return sb.toString();
@@ -318,9 +315,8 @@ class FSImageLoader {
    * @throws IOException if failed to serialize ContentSummary to JSON.
    */
   String getContentSummary(String path) throws IOException {
-    ObjectMapper mapper = new ObjectMapper();
     return "{\"ContentSummary\":\n"
-        + mapper.writeValueAsString(getContentSummaryMap(path)) + "\n}\n";
+        + JsonUtil.toJsonString(getContentSummaryMap(path)) + "\n}\n";
   }
 
   private Map<String, Object> getContentSummaryMap(String path)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/JsonUtil.java

@@ -389,4 +389,8 @@ public class JsonUtil {
     return MAPPER.writeValueAsString(finalMap);
   }
 
+  public static String toJsonString(Object obj) throws IOException {
+    return MAPPER.writeValueAsString(obj);
+  }
+
 }