Applying Metadata to HDFS and Hive Entities using the API

Using the Navigator API and JSON formatted metadata definition files, entities can be assigned properties in bulk, prior to extraction.

Metadata Definition Files

You can add tags and properties to HDFS entities using metadata files. With metadata files, you can assign metadata to entities in bulk and create metadata before it is extracted. A metadata file is a JSON file with the following structure:

{
  "name" : "name",
  "description" : "description",
  "properties" : {
    "key_name_1" : "value_1", 
        "key_name_2" : "value_2"
  },
  "tags" : [ "tag_1" ]
}
To add metadata files to files and directories, create a metadata file with the extension .navigator, naming the files as follows:
  • File - The path of the metadata file must be .filename.navigator. For example, to apply properties to the file /user/test/file1.txt, the metadata file path is /user/test/.file1.txt.navigator.
  • Directory - The path of the metadata file must be dirpath/.navigator. For example, to apply properties to the directory /user, the metadata path must be /user/.navigator.
The metadata file is applied to the entity metadata when the extractor runs.

Applying HDFS and Hive Metadata

The Navigator APIs can be used modify metadata of HDFS or Hive entities before or after entity extraction.
  • If an entity has been extracted when the API is called, the metadata is applied immediately.
  • If the entity has not been extracted, you can preregister metadata, which is then applied once the entity is extracted.

Metadata is saved regardless of whether or not a matching entity is extracted. Cloudera Navigator does not perform any cleanup of unused metadata.

If you call the API before the entity is extracted, the custom metadata is stored with the entity's:
  • Identity
  • Source ID
  • Metadata fields (name, description, tags, properties)
  • Fields relevant to the identifier
Other fields (attributes) for the entity, such as Type, are not present.
To view all stored metadata, use the API to search for entities without an internal type, specifically the entities endpoint with the GET method:
http://fqdn-n.example.com:port/api/APIversion/entities/ 

where fqdn-n.example.com is the host running the Navigator Metadata Server role instance listening for HTTP connections at the specified port number (7187 is the default port number). APIversion is the running version of the API as indicated in the footer of the API documentation (available from the Help menu in the Navigator console) or by calling http://fqdn-n.example.com:port/api/version.

For example:

curl http://node1.example.com:7187/api/v13/entities/?query=-internalType:* \
-u username:password -X GET

Custom metadata provided through the API overwrites existing metadata. For example, passing empty name and description fields with an empty array for tags and empty property dictionary with the API call removes the metadata. If you omit the tags or properties fields, the existing values remain unchanged.

Modifying custom metadata using metadata files and the metadata API at the same time is not supported. You must use one or the other, because the two methods work differently.

Metadata specified in JSON files is merged with existing metadata, whereas the API overwrites metadata. Also, the updates provided by metadata files wait in a queue before being merged, but API changes are committed immediately. Some inconsistency can occur if a metadata file is merged when the API is in use.

Metadata is modified using either the PUT or POST method. Use the PUT method if the entity has been extracted, and the POST method to preregister metadata. Use the following syntax:
  • PUT
    curl http://fqdn-n.example.com:port/api/APIversion/entities/identity \
    -u username:password \
    -X PUT \
    -H "Content-Type: application/json" \
    -d '{properties}'
    where identity is an entity ID and properties are:
    • name - Name metadata.
    • description - Description metadata.
    • tags - Tag metadata.
    • properties - Custom metadata properties. The format is {key: value}.
    • customProperties - Managed metadata properties. The format is {namespace: {key: value}}. If a property is assigned a value that does not conform to type constraints, an error is returned.
    All existing naming rules apply, and if any value is invalid, the entire request is denied.
  • POST
    curl http://fqdn-n.example.com:port/api/APIversion/entities/ \
    -u username:password \
    -X POST \
    -H "Content-Type: application/json" \
    -d '{properties}'
    where properties are:
    • sourceId (required) - An existing source ID. After the first extraction, you can retrieve source IDs using the call:
      curl http://fqdn-n.example.com:port/api/APIversion/entities/?query=type:SOURCE \
      -u username:password -X GET
      For example:
      [ ...
      {  {
      "identity": "61cfefd303d4284b7f5014b701f2c76d",
      "originalName": "source.listing",
      "originalDescription": null,
      "sourceId": "012437f9eeb3c23dc69e679ac94a7fa2",
      "firstClassParentId": null,
      "parentPath": "/user/hdfs/.cm/distcp/2016-02-03_487",
      ...
      "properties": {
      "__cloudera_internal__hueLink":
      "http://fqdn-2.example.com:8888/filebrowser/#/user/hdfs/.cm/distcp/2016-02-03_487/source.listing"
       },
      "technicalProperties": null,
      "fileSystemPath": "/user/hdfs/.cm/distcp/2016-02-03_487/source.listing",
      "type": "FILE",
      "size": 92682,
      "created": "2016-02-03T21:12:16.587Z",
      "lastModified": "2016-02-03T21:12:16.587Z",
      "lastAccessed": "2016-02-03T21:12:16.587Z",
      "permissions": "rw-r--r--",
      "owner": "hdfs",
      "group": "supergroup",
      "blockSize": 134217728,
      "mimeType": "application/octet-stream",
      "replication": 3,
      "userEntity": false,
      "deleted": false,
      "sourceType": "HDFS",
      "metaClassName": "fselement",
      "packageName": "nav",
      "internalType": "fselement"
      }, ...
      If you have multiple services of a given type, you must specify the source ID that contains the entity you expect it to match.
    • parentPath - The path of the parent entity, defined as:
      • HDFS file or directory - fileSystemPath of the parent directory. (Do not provide this field if the entity affected is the root directory.) Example parentPath for /user/admin/input_dir: /user/admin. If you add metadata to a directory, the metadata does not propagate to any files or folders in that directory.
      • Hive database - If you are updating database metadata, do not specify this field.
      • Hive table or view - The name of database containing the table or view. Example for a table in the default database: default.
      • Hive column - database name/table name/view name. Example for a column in the sample_07 table: default/sample_07.
    • originalName (required) - The name as defined by the source system.
      • HDFS file or directory- Name of file or directory (ROOT if the entity is the root directory). Example originalName for /user/admin/input_dir: input_dir.
      • Hive database, table, view, or column - The name of the database, table, view, or column.
        • Example for default database: default
        • Example for sample_07 table: sample_07
    • identity
    • Metadata fields (name, description, tags, properties)
    • Fields relevant to the identifier
All existing naming rules apply, and if any value is invalid, the entire request is denied.

API Usage Examples

HDFS PUT Custom Metadata Example for /user/admin/input_dir Directory

curl http://node1.example.com:7187/api/v13/entities/e461de8de38511a3ac6740dd7d51b8d0 \
-u username:password \
-X PUT \
-H "Content-Type: application/json"\
-d '{"name":"my_name",
   "description":"My description",
   "tags":["tag1","tag2"],
   "properties":{"property1":"value1","property2":"value2"}}'

HDFS POST Custom Metadata Example for /user/admin/input_dir Directory

curl http://node1.example.com:7187/api/v13/entities/ \
-u username:password \
-X POST \
-H "Content-Type: application/json" \
-d '{"sourceId":"a09b0233cc58ff7d601eaa68673a20c6",
     "parentPath":"/user/admin",
     "originalName":"input_dir",
     "name":"my_name",
     "description":"My description",
     "tags":["tag1","tag2"],
     "properties":{"property1":"value1","property2":"value2"}}'

Hive POST Custom Metadata Example for total_emp Column

curl http://node1.example.com:7187/api/v13/entities/\
-u username:password \
-X POST \
-H "Content-Type: application/json" \
-d '{"sourceId":"4fbdadc6899638782fc8cb626176dc7b",
     "parentPath":"default/sample_07",
     "originalName":"total_emp",
     "name":"my_name",
     "description":"My description",
     "tags":["tag1","tag2"],
     "properties":{"property1":"value1","property2":"value2"}}'

HDFS PUT Managed Metadata Example

This example adds two new properties to the MailAnnotation namespace. The emailTo property is multivalued to handle multiple addressees, while the emailFrom property supports a single value:
curl http://node1.example.com:7187/api/v13/entities/87afcb92d5de856c7e8292e2e12cf1ea \
-u username:password \
-X PUT \
-H "Content-Type: application/json" \
-d '{"customProperties":{"MailAnnotation":
    {"emailTo":["lee@example.com","dana@example.com"],
     "emailFrom":"terry@email.com"}}}'
The server responds:
{
  "identity" : "87afcb92d5de856c7e8292e2e12cf1ea",
  "originalName" : "years",
  "originalDescription" : null,
  "sourceId" : "012437f9eeb3c23dc69e679ac94a7fa2",
  "firstClassParentId" : null,
  "parentPath" : "/user/admin",
  "extractorRunId" : "012437f9eeb3c23dc69e679ac94a7fa2##1",
  "customProperties" : {
    "MailAnnotation" : {
      "emailTo" : [ "lee@example.com", "dana@example.com" ],
      "emailFrom" : "terry@email.com"
    }
  },
  "name" : null,
  "description" : null,
  "tags" : null,
  "properties" : {
    "__cloudera_internal__hueLink" : "hue_server_host:8888/filebrowser/#/user/admin/years"
  },
  "technicalProperties" : null,
  "fileSystemPath" : "/user/admin/years",
  "type" : "DIRECTORY",
  "size" : null,
  "created" : "2016-03-22T17:55:31.902Z",
  "lastModified" : "2016-03-22T17:59:14.065Z",
  "lastAccessed" : null,
  "permissions" : "rwxr-xr-x",
  "owner" : "hdfs",
  "group" : "admin",
  "blockSize" : null,
  "mimeType" : null,
  "replication" : null,
  "sourceType" : "HDFS",
  "metaClassName" : "fselement",
  "userEntity" : false,
  "deleted" : false,
  "packageName" : "nav",
  "internalType" : "fselement"
}

Using the Cloudera Navigator SDK for Metadata Management

To facilitate working with metadata using the Cloudera Navigator APIs, Cloudera provides the Cloudera Navigator SDK. Cloudera Navigator SDK is a client library that provides functionality for extracting and enriching metadata with custom models, entities, and relationships. See GitHub cloudera/navigator-sdk for details.