WebHDFS REST API

The HTTP REST API supports the complete FileSystem interface for HDFS. The operations and the corresponding FileSystem methods are shown in the next section. The Section HTTP Query Parameter Dictionary specifies the parameter details such as the defaults and the valid values.

Operations

• HTTP GET
  • OPEN (see FileSystem.open)
  • GETFILESTATUS (see FileSystem.getFileStatus)
  • LISTSTATUS (see FileSystem.listStatus)
  • GETCONTENTSUMMARY (see FileSystem.getContentSummary)
  • GETFILECHECKSUM (see FileSystem.getFileChecksum)
  • GETHOMEDIRECTORY (see FileSystem.getHomeDirectory)
  • GETDELEGATIONTOKEN (see FileSystem.getDelegationToken)
• HTTP PUT
  • CREATE (see FileSystem.create)
  • MKDIRS (see FileSystem.mkdirs)
  • RENAME (see FileSystem.rename)
  • SETREPLICATION (see FileSystem.setReplication)
  • SETOWNER (see FileSystem.setOwner)
  • SETPERMISSION (see FileSystem.setPermission)
  • SETTIMES (see FileSystem.setTimes)
  • RENEWDELEGATIONTOKEN (see DistributedFileSystem.renewDelegationToken)
  • CANCELDELEGATIONTOKEN (see DistributedFileSystem.cancelDelegationToken)
• HTTP POST
  • APPEND (see FileSystem.append)
• HTTP DELETE
  • DELETE (see FileSystem.delete)

FileSystem URIs vs HTTP URLs

The FileSystem scheme of WebHDFS is "webhdfs://". A WebHDFS FileSystem URI has the following format.

  webhdfs://<HOST>:<HTTP_PORT>/<PATH>

The above WebHDFS URI corresponds to the below HDFS URI.

  hdfs://<HOST>:<RPC_PORT>/<PATH>

In the REST API, the prefix "/webhdfs/v1" is inserted in the path and a query is appended at the end. Therefore, the corresponding HTTP URL has the following format.

  http://<HOST>:<HTTP_PORT>/webhdfs/v1/<PATH>?op=...

HDFS Configuration Options

Below are the HDFS configuration options for WebHDFS.

When security is off, the authenticated user is the username specified in the user.name query parameter. If the user.name parameter is not set, the server may either set the authenticated user to a default web user, if there is any, or return an error response.

When security is on, authentication is performed by either Hadoop delegation token or Kerberos SPNEGO. If a token is set in the delegation query parameter, the authenticated user is the user encoded in the token. If the delegation parameter is not set, the user is authenticated by Kerberos SPNEGO.

Below are examples using the curl command tool.

1. Authentication when security is off:

   curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?[user.name=<USER>&]op=..."
       

2. Authentication using Kerberos SPNEGO when security is on:

   curl -i --negotiate -u : "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=..."
       

3. Authentication using Hadoop delegation token when security is on:

   curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?delegation=<TOKEN>&op=..."
       

When the proxy user feature is enabled, a proxy user P may submit a request on behalf of another user U. The username of U must be specified in the doas query parameter unless a delegation token is presented in authentication. In such case, the information of both users P and U must be encoded in the delegation token.

1. A proxy request when security is off:

   curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?[user.name=<USER>&]doas=<USER>&op=..."
       

2. A proxy request using Kerberos SPNEGO when security is on:

   curl -i --negotiate -u : "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?doas=<USER>&op=..."
       

3. A proxy request using Hadoop delegation token when security is on:

   curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?delegation=<TOKEN>&op=..."
       

Create and Write to a File

• Step 1: Submit a HTTP PUT request without automatically following redirects and without sending the file data.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=CREATE
                      [&overwrite=<true|false>][&blocksize=<LONG>][&replication=<SHORT>]
                      [&permission=<OCTAL>][&buffersize=<INT>]"
      

  The request is redirected to a datanode where the file data is to be written:

  HTTP/1.1 307 TEMPORARY_REDIRECT
  Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=CREATE...
  Content-Length: 0
      

• Step 2: Submit another HTTP PUT request using the URL in the Location header with the file data to be written.

  curl -i -X PUT -T <LOCAL_FILE> "http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=CREATE..."
      

  The client receives a 201 Created response with zero content length and the WebHDFS URI of the file in the Location header:

  HTTP/1.1 201 Created
  Location: webhdfs://<HOST>:<PORT>/<PATH>
  Content-Length: 0
      

Note that the reason of having two-step create/append is for preventing clients to send out data before the redirect. This issue is addressed by the "Expect: 100-continue" header in HTTP/1.1; see RFC 2616, Section 8.2.3. Unfortunately, there are software library bugs (e.g. Jetty 6 HTTP server and Java 6 HTTP client), which do not correctly implement "Expect: 100-continue". The two-step create/append is a temporary workaround for the software library bugs.

See also: overwrite, blocksize, replication, permission, buffersize, FileSystem.create

Append to a File

• Step 1: Submit a HTTP POST request without automatically following redirects and without sending the file data.

  curl -i -X POST "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=APPEND[&buffersize=<INT>]"
      

  The request is redirected to a datanode where the file data is to be appended:

  HTTP/1.1 307 TEMPORARY_REDIRECT
  Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=APPEND...
  Content-Length: 0
      

• Step 2: Submit another HTTP POST request using the URL in the Location header with the file data to be appended.

  curl -i -X POST -T <LOCAL_FILE> "http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=APPEND..."
      

  The client receives a response with zero content length:

  HTTP/1.1 200 OK
  Content-Length: 0
      

See the note in the previous section for the description of why this operation requires two steps.

See also: buffersize, FileSystem.append

Open and Read a File

• Submit a HTTP GET request with automatically following redirects.

  curl -i -L "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=OPEN
                      [&offset=<LONG>][&length=<LONG>][&buffersize=<INT>]"
      

  The request is redirected to a datanode where the file data can be read:

  HTTP/1.1 307 TEMPORARY_REDIRECT
  Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=OPEN...
  Content-Length: 0
      

  The client follows the redirect to the datanode and receives the file data:

  HTTP/1.1 200 OK
  Content-Type: application/octet-stream
  Content-Length: 22
  
  Hello, webhdfs user!
      

See also: offset, length, buffersize, FileSystem.open

Make a Directory

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/<PATH>?op=MKDIRS[&permission=<OCTAL>]"
      

  The client receives a response with a boolean JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {"boolean": true}
      

See also: permission, FileSystem.mkdirs

Rename a File/Directory

• Submit a HTTP PUT request.

  curl -i -X PUT "<HOST>:<PORT>/webhdfs/v1/<PATH>?op=RENAME&destination=<PATH>"
      

  The client receives a response with a boolean JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {"boolean": true}
      

See also: destination, FileSystem.rename

Delete a File/Directory

• Submit a HTTP DELETE request.

  curl -i -X DELETE "http://<host>:<port>/webhdfs/v1/<path>?op=DELETE
                                [&recursive=<true|false>]"
      

  The client receives a response with a boolean JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {"boolean": true}
      

See also: recursive, FileSystem.delete

Status of a File/Directory

• Submit a HTTP GET request.

  curl -i  "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=GETFILESTATUS"
      

  The client receives a response with a FileStatus JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {
    "FileStatus":
    {
      "accessTime"      : 0,
      "blockSize"       : 0,
      "group"           : "supergroup",
      "length"          : 0,             //in bytes, zero for directories
      "modificationTime": 1320173277227,
      "owner"           : "webuser",
      "pathSuffix"      : "",
      "permission"      : "777",
      "replication"     : 0,
      "type"            : "DIRECTORY"    //enum {FILE, DIRECTORY}
    }
  }
      

See also: FileSystem.getFileStatus

List a Directory

• Submit a HTTP GET request.

  curl -i  "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=LISTSTATUS"
      

  The client receives a response with a FileStatuses JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Content-Length: 427
  
  {
    "FileStatuses":
    {
      "FileStatus":
      [
        {
          "accessTime"      : 1320171722771,
          "blockSize"       : 33554432,
          "group"           : "supergroup",
          "length"          : 24930,
          "modificationTime": 1320171722771,
          "owner"           : "webuser",
          "pathSuffix"      : "a.patch",
          "permission"      : "644",
          "replication"     : 1,
          "type"            : "FILE"
        },
        {
          "accessTime"      : 0,
          "blockSize"       : 0,
          "group"           : "supergroup",
          "length"          : 0,
          "modificationTime": 1320895981256,
          "owner"           : "szetszwo",
          "pathSuffix"      : "bar",
          "permission"      : "711",
          "replication"     : 0,
          "type"            : "DIRECTORY"
        },
        ...
      ]
    }
  }
      

See also: FileSystem.listStatus

Get Content Summary of a Directory

• Submit a HTTP GET request.

  curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=GETCONTENTSUMMARY"
      

  The client receives a response with a ContentSummary JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {
    "ContentSummary":
    {
      "directoryCount": 2,
      "fileCount"     : 1,
      "length"        : 24930,
      "quota"         : -1,
      "spaceConsumed" : 24930,
      "spaceQuota"    : -1
    }
  }
      

See also: FileSystem.getContentSummary

Get File Checksum

• Submit a HTTP GET request.

  curl -i "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=GETFILECHECKSUM"
      

  The request is redirected to a datanode:

  HTTP/1.1 307 TEMPORARY_REDIRECT
  Location: http://<DATANODE>:<PORT>/webhdfs/v1/<PATH>?op=GETFILECHECKSUM...
  Content-Length: 0
      

  The client follows the redirect to the datanode and receives a FileChecksum JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {
    "FileChecksum":
    {
      "algorithm": "MD5-of-1MD5-of-512CRC32",
      "bytes"    : "eadb10de24aa315748930df6e185c0d ...",
      "length"   : 28
    }
  }
      

See also: FileSystem.getFileChecksum

Get Home Directory

• Submit a HTTP GET request.

  curl -i "http://<HOST>:<PORT>/webhdfs/v1/?op=GETHOMEDIRECTORY"
      

  The client receives a response with a Path JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {"Path": "/user/szetszwo"}
      

See also: FileSystem.getHomeDirectory

Set Permission

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=SETPERMISSION
                                [&permission=<OCTAL>]"
      

  The client receives a response with zero content length:

  HTTP/1.1 200 OK
  Content-Length: 0
      

See also: permission, FileSystem.setPermission

Set Owner

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=SETOWNER
                                [&owner=<USER>][&group=<GROUP>]"
      

  The client receives a response with zero content length:

  HTTP/1.1 200 OK
  Content-Length: 0
      

See also: owner, group, FileSystem.setOwner

Set Replication Factor

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=SETREPLICATION
                                [&replication=<SHORT>]"
      

  The client receives a response with a boolean JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {"boolean": true}
      

See also: replication, FileSystem.setReplication

Set Access or Modification Time

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/<PATH>?op=SETTIMES
                                [&modificationtime=<TIME>][&accesstime=<TIME>]"
      

  The client receives a response with zero content length:

  HTTP/1.1 200 OK
  Content-Length: 0
      

See also: modificationtime, accesstime, FileSystem.setTimes

Get Delegation Token

• Submit a HTTP GET request.

  curl -i "http://<HOST>:<PORT>/webhdfs/v1/?op=GETDELEGATIONTOKEN&renewer=<USER>"
      

  The client receives a response with a Token JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {
    "Token":
    {
      "urlString": "JQAIaG9y..."
    }
  }
      

See also: renewer, FileSystem.getDelegationToken

Renew Delegation Token

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/?op=RENEWDELEGATIONTOKEN&token=<TOKEN>"
      

  The client receives a response with a long JSON object:

  HTTP/1.1 200 OK
  Content-Type: application/json
  Transfer-Encoding: chunked
  
  {"long": 1320962673997}           //the new expiration time
      

See also: token, DistributedFileSystem.renewDelegationToken

Cancel Delegation Token

• Submit a HTTP PUT request.

  curl -i -X PUT "http://<HOST>:<PORT>/webhdfs/v1/?op=CANCELDELEGATIONTOKEN&token=<TOKEN>"
      

  The client receives a response with zero content length:

  HTTP/1.1 200 OK
  Content-Length: 0
      

See also: token, DistributedFileSystem.cancelDelegationToken

When an operation fails, the server may throw an exception. The JSON schema of error responses is defined in RemoteException JSON schema. The table below shows the mapping from exceptions to HTTP response codes.

HTTP Response Codes

Below are examples of exception responses.

Illegal Argument Exception

HTTP/1.1 400 Bad Request
Content-Type: application/json
Transfer-Encoding: chunked

{
  "RemoteException":
  {
    "exception"    : "IllegalArgumentException",
    "javaClassName": "java.lang.IllegalArgumentException",
    "message"      : "Invalid value for webhdfs parameter \"permission\": ..."
  }
}

Security Exception

HTTP/1.1 401 Unauthorized
Content-Type: application/json
Transfer-Encoding: chunked

{
  "RemoteException":
  {
    "exception"    : "SecurityException",
    "javaClassName": "java.lang.SecurityException",
    "message"      : "Failed to obtain user group information: ..."
  }
}

Access Control Exception

HTTP/1.1 403 Forbidden
Content-Type: application/json
Transfer-Encoding: chunked

{
  "RemoteException":
  {
    "exception"    : "AccessControlException",
    "javaClassName": "org.apache.hadoop.security.AccessControlException",
    "message"      : "Permission denied: ..."
  }
}

File Not Found Exception

HTTP/1.1 404 Not Found
Content-Type: application/json
Transfer-Encoding: chunked

{
  "RemoteException":
  {
    "exception"    : "FileNotFoundException",
    "javaClassName": "java.io.FileNotFoundException",
    "message"      : "File does not exist: /foo/a.patch"
  }
}

All operations, except for OPEN, either return a zero-length response or a JSON response . For OPEN, the response is an octet-stream. The JSON schemas are shown below. See draft-zyp-json-schema-03 for the syntax definitions of the JSON schemas.

Boolean JSON Schema

{
  "name"      : "boolean",
  "properties":
  {
    "boolean":
    {
      "description": "A boolean value",
      "type"       : "boolean",
      "required"   : true
    }
  }
}

See also: MKDIRS, RENAME, DELETE, SETREPLICATION

ContentSummary JSON Schema

{
  "name"      : "ContentSummary",
  "properties":
  {
    "ContentSummary":
    {
      "type"      : "object",
      "properties":
      {
        "directoryCount":
        {
          "description": "The number of directories.",
          "type"       : "integer",
          "required"   : true
        },
        "fileCount":
        {
          "description": "The number of files.",
          "type"       : "integer",
          "required"   : true
        },
        "length":
        {
          "description": "The number of bytes used by the content.",
          "type"       : "integer",
          "required"   : true
        },
        "quota":
        {
          "description": "The namespace quota of this directory.",
          "type"       : "integer",
          "required"   : true
        },
        "spaceConsumed":
        {
          "description": "The disk space consumed by the content.",
          "type"       : "integer",
          "required"   : true
        },
        "spaceQuota":
        {
          "description": "The disk space quota.",
          "type"       : "integer",
          "required"   : true
        }
      }
    }
  }
}

See also: GETCONTENTSUMMARY

FileChecksum JSON Schema

{
  "name"      : "FileChecksum",
  "properties":
  {
    "FileChecksum":
    {
      "type"      : "object",
      "properties":
      {
        "algorithm":
        {
          "description": "The name of the checksum algorithm.",
          "type"       : "string",
          "required"   : true
        },
        "bytes":
        {
          "description": "The byte sequence of the checksum in hexadecimal.",
          "type"       : "string",
          "required"   : true
        },
        "length":
        {
          "description": "The length of the bytes (not the length of the string).",
          "type"       : "integer",
          "required"   : true
        }
      }
    }
  }
}

See also: GETFILECHECKSUM

FileStatus JSON Schema

{
  "name"      : "FileStatus",
  "properties":
  {
    "FileStatus": fileStatusProperties      //See FileStatus Properties
  }
}

See also: GETFILESTATUS, FileStatus

FileStatus Properties

JavaScript syntax is used to define fileStatusProperties so that it can be referred in both FileStatus and FileStatuses JSON schemas.

var fileStatusProperties =
{
  "type"      : "object",
  "properties":
  {
    "accessTime":
    {
      "description": "The access time.",
      "type"       : "integer",
      "required"   : true
    },
    "blockSize":
    {
      "description": "The block size of a file.",
      "type"       : "integer",
      "required"   : true
    },
    "group":
    {
      "description": "The group owner.",
      "type"       : "string",
      "required"   : true
    },
    "length":
    {
      "description": "The number of bytes in a file.",
      "type"       : "integer",
      "required"   : true
    },
    "modificationTime":
    {
      "description": "The modification time.",
      "type"       : "integer",
      "required"   : true
    },
    "owner":
    {
      "description": "The user who is the owner.",
      "type"       : "string",
      "required"   : true
    },
    "pathSuffix":
    {
      "description": "The path suffix.",
      "type"       : "string",
      "required"   : true
    },
    "permission":
    {
      "description": "The permission represented as a octal string.",
      "type"       : "string",
      "required"   : true
    },
    "replication":
    {
      "description": "The number of replication of a file.",
      "type"       : "integer",
      "required"   : true
    },
   "type":
    {
      "description": "The type of the path object.",
      "enum"       : ["FILE", "DIRECTORY"],
      "required"   : true
    }
  }
};

FileStatuses JSON Schema

A FileStatuses JSON object represents an array of FileStatus JSON objects.

{
  "name"      : "FileStatuses",
  "properties":
  {
    "FileStatuses":
    {
      "type"      : "object",
      "properties":
      {
        "FileStatus":
        {
          "description": "An array of FileStatus",
          "type"       : "array",
          "items"      : fileStatusProperties      //See FileStatus Properties
        }
      }
    }
  }
}

See also: LISTSTATUS, FileStatus

Long JSON Schema

{
  "name"      : "long",
  "properties":
  {
    "long":
    {
      "description": "A long integer value",
      "type"       : "integer",
      "required"   : true
    }
  }
}

See also: RENEWDELEGATIONTOKEN,

Path JSON Schema

{
  "name"      : "Path",
  "properties":
  {
    "Path":
    {
      "description": "The string representation a Path.",
      "type"       : "string",
      "required"   : true
    }
  }
}

See also: GETHOMEDIRECTORY, Path

RemoteException JSON Schema

{
  "name"      : "RemoteException",
  "properties":
  {
    "RemoteException":
    {
      "type"      : "object",
      "properties":
      {
        "exception":
        {
          "description": "Name of the exception",
          "type"       : "string",
          "required"   : true
        },
        "message":
        {
          "description": "Exception message",
          "type"       : "string",
          "required"   : true
        },
        "javaClassName":                                     //an optional property
        {
          "description": "Java class name of the exception",
          "type"       : "string",
        }
      }
    }
  }
}

Token JSON Schema

{
  "name"      : "Token",
  "properties":
  {
    "Token":
    {
      "type"      : "object",
      "properties":
      {
        "urlString":
        {
          "description": "A delegation token encoded as a URL safe string.",
          "type"       : "string",
          "required"   : true
        }
      }
    }
  }
}

See also: GETDELEGATIONTOKEN, the note in Delegation.

Access Time

See also: SETTIMES

Block Size

See also: CREATE

Buffer Size

See also: CREATE, APPEND, OPEN

Delegation

Note that delegation tokens are encoded as a URL safe string; see encodeToUrlString() and decodeFromUrlString(String) in org.apache.hadoop.security.token.Token for the details of the encoding.

See also: Authentication

Destination

See also: RENAME

Do As

See also: Proxy Users

Group

See also: SETOWNER

Length

See also: OPEN

Modification Time

See also: SETTIMES

Offset

See also: OPEN

Op

See also: Operations

Overwrite

See also: CREATE

Owner

See also: SETOWNER

Permission

See also: CREATE, MKDIRS, SETPERMISSION

Recursive

See also: RENAME

Renewer

See also: GETDELEGATIONTOKEN

Replication

See also: CREATE, SETREPLICATION

Token

See also: RENEWDELEGATIONTOKEN, CANCELDELEGATIONTOKEN

Username

See also: Authentication