HDFS-17029. Support getECPolices API in WebHDFS (#5698). Contributed by Hualong Zhang.

Reviewed-by: Shilun Fan <slfan1989@apache.org>
Reviewed-by: Tao Li <tomscut@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

@@ -42,6 +42,8 @@ import org.apache.hadoop.hdfs.DFSUtilClient;
 import org.apache.hadoop.hdfs.protocol.BlockStoragePolicy;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicy;
+import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicyInfo;
+import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicyState;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReportListing;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReportListing.DiffReportListingEntry;
@@ -835,6 +837,36 @@ public class JsonUtilClient {
     return new FsStatus(capacity, used, remaining);
   }
 
+  public static Collection<ErasureCodingPolicyInfo> getAllErasureCodingPolicies(
+      Map<?, ?> json) {
+    Map<?, ?> erasureCodingPoliciesJson = (Map<?, ?>) json.get("ErasureCodingPolicies");
+    if (erasureCodingPoliciesJson != null) {
+      List<?> objs = (List<?>) erasureCodingPoliciesJson.get(ErasureCodingPolicyInfo.class
+          .getSimpleName());
+      if (objs != null) {
+        ErasureCodingPolicyInfo[] erasureCodingPolicies = new ErasureCodingPolicyInfo[objs
+            .size()];
+        for (int i = 0; i < objs.size(); i++) {
+          final Map<?, ?> m = (Map<?, ?>) objs.get(i);
+          ErasureCodingPolicyInfo erasureCodingPolicyInfo = toECPolicyInfo(m);
+          erasureCodingPolicies[i] = erasureCodingPolicyInfo;
+        }
+        return Arrays.asList(erasureCodingPolicies);
+      }
+    }
+    return new ArrayList<ErasureCodingPolicyInfo>(0);
+  }
+
+  public static ErasureCodingPolicyInfo toECPolicyInfo(Map<?, ?> m) {
+    if (m == null) {
+      return null;
+    }
+    ErasureCodingPolicy ecPolicy = toECPolicy((Map<?, ?>) m.get("policy"));
+    String state = getString(m, "state", "DISABLE");
+    final ErasureCodingPolicyState ecPolicyState = ErasureCodingPolicyState.valueOf(state);
+    return new ErasureCodingPolicyInfo(ecPolicy, ecPolicyState);
+  }
+
   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

@@ -100,6 +100,7 @@ import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.protocol.BlockStoragePolicy;
 import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicy;
+import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicyInfo;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
@@ -2192,6 +2193,19 @@ public class WebHdfsFileSystem extends FileSystem
     }.run();
   }
 
+  public Collection<ErasureCodingPolicyInfo> getAllErasureCodingPolicies()
+      throws IOException {
+    statistics.incrementReadOps(1);
+    storageStatistics.incrementOpCounter(OpType.GET_EC_POLICIES);
+    final GetOpParam.Op op = GetOpParam.Op.GETECPOLICIES;
+    return new FsPathResponseRunner<Collection<ErasureCodingPolicyInfo>>(op, null) {
+      @Override
+      Collection<ErasureCodingPolicyInfo> decodeResponse(Map<?, ?> json) {
+        return JsonUtilClient.getAllErasureCodingPolicies(json);
+      }
+    }.run();
+  }
+
   @VisibleForTesting
   InetSocketAddress[] getResolvedNNAddr() {
     return nnAddrs;

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

@@ -67,6 +67,7 @@ public class GetOpParam extends HttpOpParam<GetOpParam.Op> {
     GETLINKTARGET(false, HttpURLConnection.HTTP_OK),
     GETFILELINKSTATUS(false, HttpURLConnection.HTTP_OK),
     GETSTATUS(false, HttpURLConnection.HTTP_OK),
+    GETECPOLICIES(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

@@ -85,6 +85,7 @@ import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.EncryptionZone;
 import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicy;
+import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicyInfo;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
@@ -1407,6 +1408,11 @@ public class NamenodeWebHdfsMethods {
       final String js = JsonUtil.toJsonString(status);
       return Response.ok(js).type(MediaType.APPLICATION_JSON).build();
     }
+    case GETECPOLICIES: {
+      ErasureCodingPolicyInfo[] ecPolicyInfos = cp.getErasureCodingPolicies();
+      final String js = JsonUtil.toJsonString(ecPolicyInfos);
+      return Response.ok(js).type(MediaType.APPLICATION_JSON).build();
+    }
     default:
       throw new UnsupportedOperationException(op + " is not supported");
     }

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

@@ -741,4 +741,27 @@ public class JsonUtil {
     m.put("remaining", status.getRemaining());
     return m;
   }
+
+  public static Map<String, Object> toJsonMap(ErasureCodingPolicyInfo ecPolicyInfo) {
+    if (ecPolicyInfo == null) {
+      return null;
+    }
+    Map<String, Object> m = new HashMap<>();
+    m.put("policy", ecPolicyInfo.getPolicy());
+    m.put("state", ecPolicyInfo.getState());
+    return m;
+  }
+
+  public static String toJsonString(ErasureCodingPolicyInfo[] ecPolicyInfos) {
+    final Map<String, Object> erasureCodingPolicies = new HashMap<>();
+    Object[] erasureCodingPolicyInfos = null;
+    if (ecPolicyInfos != null && ecPolicyInfos.length > 0) {
+      erasureCodingPolicyInfos = new Object[ecPolicyInfos.length];
+      for (int i = 0; i < ecPolicyInfos.length; i++) {
+        erasureCodingPolicyInfos[i] = toJsonMap(ecPolicyInfos[i]);
+      }
+    }
+    erasureCodingPolicies.put("ErasureCodingPolicyInfo", erasureCodingPolicyInfos);
+    return toJsonString("ErasureCodingPolicies", erasureCodingPolicies);
+  }
 }

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

@@ -61,6 +61,7 @@ The HTTP REST API supports the complete [FileSystem](../../api/org/apache/hadoop
     * [`GETLINKTARGET`](#Get_Link_Target) (see [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getLinkTarget)
     * [`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)
 *   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)
@@ -1191,6 +1192,44 @@ See also: [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getLinkTa
 
 See also: [FileSystem](../../api/org/apache/hadoop/fs/FileSystem.html).getFileLinkInfo
 
+### Get EC Policies
+
+* Submit a HTTP GET request.
+
+        curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=GETECPOLICIES"
+
+  The client receives a response with a [`ECPolicies` JSON object](#EC_Policies_JSON_Schema):
+
+        HTTP/1.1 200 OK
+        Content-Type: application/json
+        Transfer-Encoding: chunked
+
+        {
+          "ErasureCodingPolicies": {
+            "ErasureCodingPolicyInfo": [
+              {
+                "state": "ENABLED",
+                "policy": {
+                  "name": "RS-6-3-1024k",
+                  "schema": {
+                    "codecName": "rs",
+                    "numDataUnits": 6,
+                    "numParityUnits": 3,
+                    "extraOptions": {}
+                  },
+                  "cellSize": 1048576,
+                  "id": 1,
+                  "replicationPolicy": false,
+                  "codecName": "rs",
+                  "numDataUnits": 6,
+                  "numParityUnits": 3,
+                  "systemPolicy": true
+                }
+              }
+            ]
+          }
+        }
+
 ### Get Status
 
 * Submit a HTTP GET request.
@@ -3175,6 +3214,35 @@ var blockLocationProperties =
   }
 }
 ```
+### EC Policies JSON Schema
+
+```json
+{
+  "ErasureCodingPolicies": {
+    "ErasureCodingPolicyInfo": [
+      {
+        "state": "ENABLED",
+        "policy": {
+          "name": "RS-6-3-1024k",
+          "schema": {
+            "codecName": "rs",
+            "numDataUnits": 6,
+            "numParityUnits": 3,
+            "extraOptions": {}
+          },
+          "cellSize": 1048576,
+          "id": 1,
+          "replicationPolicy": false,
+          "codecName": "rs",
+          "numDataUnits": 6,
+          "numParityUnits": 3,
+          "systemPolicy": true
+        }
+      }
+    ]
+  }
+}
+```
 
 HTTP Query Parameter Dictionary
 -------------------------------

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

@@ -2291,6 +2291,33 @@ public class TestWebHDFS {
     }
   }
 
+  @Test
+  public void testGetErasureCodingPolicies() 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();
+
+      Collection<ErasureCodingPolicyInfo> webHdfsEcPolicyInfos =
+          webHdfs.getAllErasureCodingPolicies();
+
+      Collection<ErasureCodingPolicyInfo> dfsEcPolicyInfos =
+          dfs.getAllErasureCodingPolicies();
+
+      //Validate erasureCodingPolicyInfos are the same as DistributedFileSystem
+      assertEquals(dfsEcPolicyInfos.size(), webHdfsEcPolicyInfos.size());
+      assertTrue(dfsEcPolicyInfos.containsAll(webHdfsEcPolicyInfos));
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
   /**
    * Get FileStatus JSONObject from ListStatus response.
    */