FetchHDFS

Description:

Retrieves a file from HDFS. The content of the incoming FlowFile is replaced by the content of the file in HDFS. The file in HDFS is left intact without any changes being made to it.

Tags:

hadoop, hdfs, get, ingest, fetch, source, restricted

Properties:

In the list below, the names of required properties appear in bold. Any other properties (not in bold) are considered optional. The table also indicates any default values, and whether a property supports the NiFi Expression Language.

NameDefault ValueAllowable ValuesDescription
Hadoop Configuration ResourcesA file or comma separated list of files which contains the Hadoop file system configuration. Without this, Hadoop will search the classpath for a 'core-site.xml' and 'hdfs-site.xml' file or will revert to a default configuration.
Kerberos PrincipalKerberos principal to authenticate as. Requires nifi.kerberos.krb5.file to be set in your nifi.properties
Kerberos KeytabKerberos keytab associated with the principal. Requires nifi.kerberos.krb5.file to be set in your nifi.properties
Kerberos Relogin Period4 hoursPeriod of time which should pass before attempting a kerberos relogin
Additional Classpath ResourcesA comma-separated list of paths to files and/or directories that will be added to the classpath. When specifying a directory, all files with in the directory will be added to the classpath, but further sub-directories will not be included.
HDFS Filename${path}/${filename}The name of the HDFS file to retrieve
Supports Expression Language: true
Compression codecNONE
  • NONE No compression
  • DEFAULT Default ZLIB compression
  • BZIP BZIP compression
  • GZIP GZIP compression
  • LZ4 LZ4 compression
  • LZO LZO compression - it assumes LD_LIBRARY_PATH has been set and jar is available
  • SNAPPY Snappy compression
  • AUTOMATIC Will attempt to automatically detect the compression codec.
No Description Provided.

Relationships:

NameDescription
successFlowFiles will be routed to this relationship once they have been updated with the content of the HDFS file
comms.failureFlowFiles will be routed to this relationship if the content of the HDFS file cannot be retrieve due to a communications failure. This generally indicates that the Fetch should be tried again.
failureFlowFiles will be routed to this relationship if the content of the HDFS file cannot be retrieved and trying again will likely not be helpful. This would occur, for instance, if the file is not found or if there is a permissions issue

Reads Attributes:

None specified.

Writes Attributes:

NameDescription
hdfs.failure.reasonWhen a FlowFile is routed to 'failure', this attribute is added indicating why the file could not be fetched from HDFS

State management:

This component does not store state.

Restricted:

Provides operator the ability to retrieve any file that NiFi has access to in HDFS or the local filesystem.

Input requirement:

This component requires an incoming relationship.

See Also:

ListHDFS, GetHDFS, PutHDFS