HDFS-17083. Support getErasureCodeCodecs API in WebHDFS (#5836). Contributed by Hualong Zhang.

Reviewed-by: Shilun Fan <slfan1989@apache.org>
Signed-off-by: Ayush Saxena <ayushsaxena@apache.org>

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

@@ -75,6 +75,7 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.EnumSet;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -867,6 +868,15 @@ public class JsonUtilClient {
     return new ErasureCodingPolicyInfo(ecPolicy, ecPolicyState);
   }
 
+  public static Map<String, String> getErasureCodeCodecs(Map<?, ?> json) {
+    Map<String, String> map = new HashMap<>();
+    Map<?, ?> m = (Map<?, ?>) json.get("ErasureCodingCodecs");
+    m.forEach((key, value) -> {
+      map.put((String) key, (String) value);
+    });
+    return map;
+  }
+
   private static List<SnapshotDiffReport.DiffReportEntry> toDiffList(
       List<?> objs) {
     if (objs == null) {

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

@@ -2206,6 +2206,19 @@ public class WebHdfsFileSystem extends FileSystem
     }.run();
   }
 
+  public Map<String, String> getAllErasureCodingCodecs()
+      throws IOException {
+    statistics.incrementReadOps(1);
+    storageStatistics.incrementOpCounter(OpType.GET_EC_CODECS);
+    final HttpOpParam.Op op = GetOpParam.Op.GETECCODECS;
+    return new FsPathResponseRunner<Map<String, String>>(op, null) {
+      @Override
+      Map<String, String> decodeResponse(Map<?, ?> json) {
+        return JsonUtilClient.getErasureCodeCodecs(json);
+      }
+    }.run();
+  }
+
   @VisibleForTesting
   InetSocketAddress[] getResolvedNNAddr() {
     return nnAddrs;

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/resources/GetOpParam.java

@@ -68,6 +68,7 @@ public class GetOpParam extends HttpOpParam<GetOpParam.Op> {
     GETFILELINKSTATUS(false, HttpURLConnection.HTTP_OK),
     GETSTATUS(false, HttpURLConnection.HTTP_OK),
     GETECPOLICIES(false, HttpURLConnection.HTTP_OK),
+    GETECCODECS(false, HttpURLConnection.HTTP_OK),
     GETSNAPSHOTLIST(false, HttpURLConnection.HTTP_OK);
 
     final boolean redirect;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/web/resources/NamenodeWebHdfsMethods.java

@@ -33,6 +33,7 @@ import java.util.Base64.Encoder;
 import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.ExecutionException;
 
 import javax.servlet.ServletContext;
@@ -1413,6 +1414,11 @@ public class NamenodeWebHdfsMethods {
       final String js = JsonUtil.toJsonString(ecPolicyInfos);
       return Response.ok(js).type(MediaType.APPLICATION_JSON).build();
     }
+    case GETECCODECS: {
+      Map<String, String> ecCodecs = cp.getErasureCodingCodecs();
+      final String js = JsonUtil.toJsonString("ErasureCodingCodecs", ecCodecs);
+      return Response.ok(js).type(MediaType.APPLICATION_JSON).build();
+    }
     default:
       throw new UnsupportedOperationException(op + " is not supported");
     }

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/WebHDFS.md

@@ -62,6 +62,7 @@ The HTTP REST API supports the complete [FileSystem](../../api/org/apache/hadoop
     * [`GETFILELINKSTATUS`](#Get_File_Link_Status) (see [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getFileLinkStatus)
     * [`GETSTATUS`](#Get_Status) (see [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getStatus)
     * [`GETECPOLICIES`](#Get_EC_Policies)
+    * [`GETECCODECS`](#Get_EC_Codecs)
 *   HTTP PUT
     * [`CREATE`](#Create_and_Write_to_a_File) (see [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).create)
     * [`MKDIRS`](#Make_a_Directory) (see [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).mkdirs)
@@ -1252,6 +1253,26 @@ See also: [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getFileLi
 
 See also: [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getStatus
 
+### Get EC Codecs
+
+* Submit a HTTP GET request.
+
+        curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=GETALLECCODECS"
+
+  The client receives a response with a [`ECCodecs` JSON object](#EC_Codecs_JSON_Schema):
+
+        HTTP/1.1 200 OK
+        Content-Type: application/json
+        Transfer-Encoding: chunked
+
+        {
+            "ErasureCodeCodecs": {
+                "rs": "rs_native, rs_java",
+                "rs-legacy": "rs-legacy_java",
+                "xor":"xor_native, xor_java"
+            }
+        }
+
 Storage Policy Operations
 -------------------------
 
@@ -3244,6 +3265,18 @@ var blockLocationProperties =
 }
 ```
 
+### EC Codecs JSON Schema
+
+```json
+{
+  "ErasureCodingCodecs": {
+    "rs": "rs_native, rs_java",
+    "rs-legacy": "rs-legacy_java",
+    "xor": "xor_native, xor_java"
+  }
+}
+```
+
 HTTP Query Parameter Dictionary
 -------------------------------
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestWebHDFS.java

@@ -2318,6 +2318,30 @@ public class TestWebHDFS {
     }
   }
 
+  @Test
+  public void getAllErasureCodingCodecs() throws Exception {
+    final Configuration conf = WebHdfsTestUtil.createConf();
+    cluster = new MiniDFSCluster.Builder(conf).build();
+    try {
+      cluster.waitActive();
+
+      final WebHdfsFileSystem webHdfs =
+          WebHdfsTestUtil.getWebHdfsFileSystem(conf,
+              WebHdfsConstants.WEBHDFS_SCHEME);
+
+      final DistributedFileSystem dfs = cluster.getFileSystem();
+
+      Map<String, String> webHdfsEcCodecs = webHdfs.getAllErasureCodingCodecs();
+
+      Map<String, String> dfsEcCodecs = dfs.getAllErasureCodingCodecs();
+
+      //Validate erasureCodingCodecs are the same as DistributedFileSystem
+      assertEquals(webHdfsEcCodecs, dfsEcCodecs);
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
   /**
    * Get FileStatus JSONObject from ListStatus response.
    */