ListAzureDataLakeStorage

Description:

Lists directory in an Azure Data Lake Storage Gen 2 filesystem

Tags:

azure, microsoft, cloud, storage, adlsgen2, datalake

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
ADLS CredentialsController Service API:
ADLSCredentialsService
Implementation: ADLSCredentialsControllerService
Controller Service used to obtain Azure Credentials.
Filesystem NameName of the Azure Storage File System. It is assumed to be already existing.
Supports Expression Language: true (will be evaluated using variable registry only)
Directory NameName of the Azure Storage Directory. The Directory Name cannot contain a leading '/'. The root directory can be designated by the empty string value. In case of the PutAzureDataLakeStorage processor, the directory will be created if not already existing.
Supports Expression Language: true (will be evaluated using variable registry only)
Recurse Subdirectoriestrue
  • true
  • false
Indicates whether to list files from subdirectories of the directory
File FilterOnly files whose names match the given regular expression will be listed
Supports Expression Language: true (will be evaluated using variable registry only)
Path FilterWhen 'Recurse Subdirectories' is true, then only subdirectories whose paths match the given regular expression will be scanned
Supports Expression Language: true (will be evaluated using variable registry only)
Record WriterController Service API:
RecordSetWriterFactory
Implementations: FreeFormTextRecordSetWriter
AvroRecordSetWriter
ParquetRecordSetWriter
ScriptedRecordSetWriter
JsonRecordSetWriter
RecordSetWriterLookup
CSVRecordSetWriter
XMLRecordSetWriter
Specifies the Record Writer to use for creating the listing. If not specified, one FlowFile will be created for each entity that is listed. If the Record Writer is specified, all entities will be written to a single FlowFile instead of adding attributes to individual FlowFiles.
Listing Strategytimestamps
  • Tracking Timestamps This strategy tracks the latest timestamp of listed entity to determine new/updated entities. Since it only tracks few timestamps, it can manage listing state efficiently. However, any newly added, or updated entity having timestamp older than the tracked latest timestamp can not be picked by this strategy. For example, such situation can happen in a file system if a file with old timestamp is copied or moved into the target directory without its last modified timestamp being updated. Also may miss files when multiple subdirectories are being written at the same time while listing is running.
  • Tracking Entities This strategy tracks information of all the listed entities within the latest 'Entity Tracking Time Window' to determine new/updated entities. This strategy can pick entities having old timestamp that can be missed with 'Tracing Timestamps'. Works even when multiple subdirectories are being written at the same time while listing is running. However additional DistributedMapCache controller service is required and more JVM heap memory is used. See the description of 'Entity Tracking Time Window' property for further details on how it works.
  • No Tracking This strategy lists an entity without any tracking. The same entity will be listed each time on executing this processor. It is recommended to change the default run schedule value. Any property that related to the persisting state will be disregarded.
Specify how to determine new/updated entities. See each strategy descriptions for detail.
Entity Tracking State CacheController Service API:
DistributedMapCacheClient
Implementations: HazelcastMapCacheClient
CouchbaseMapCacheClient
CassandraDistributedMapCache
HBase_1_1_2_ClientMapCacheService
RedisDistributedMapCacheClientService
DistributedMapCacheClientService
HBase_2_ClientMapCacheService
Listed entities are stored in the specified cache storage so that this processor can resume listing across NiFi restart or in case of primary node change. 'Tracking Entities' strategy require tracking information of all listed entities within the last 'Tracking Time Window'. To support large number of entities, the strategy uses DistributedMapCache instead of managed state. Cache key format is 'ListedEntities::{processorId}(::{nodeId})'. If it tracks per node listed entities, then the optional '::{nodeId}' part is added to manage state separately. E.g. cluster wide cache key = 'ListedEntities::8dda2321-0164-1000-50fa-3042fe7d6a7b', per node cache key = 'ListedEntities::8dda2321-0164-1000-50fa-3042fe7d6a7b::nifi-node3' The stored cache content is Gzipped JSON string. The cache key will be deleted when target listing configuration is changed. Used by 'Tracking Entities' strategy.
Entity Tracking Time Window3 hoursSpecify how long this processor should track already-listed entities. 'Tracking Entities' strategy can pick any entity whose timestamp is inside the specified time window. For example, if set to '30 minutes', any entity having timestamp in recent 30 minutes will be the listing target when this processor runs. A listed entity is considered 'new/updated' and a FlowFile is emitted if one of following condition meets: 1. does not exist in the already-listed entities, 2. has newer timestamp than the cached entity, 3. has different size than the cached entity. If a cached entity's timestamp becomes older than specified time window, that entity will be removed from the cached already-listed entities. Used by 'Tracking Entities' strategy.
Supports Expression Language: true (will be evaluated using variable registry only)
Entity Tracking Initial Listing Targetall
  • Tracking Time Window Ignore entities having timestamp older than the specified 'Tracking Time Window' at the initial listing activity.
  • All Available Regardless of entities timestamp, all existing entities will be listed at the initial listing activity.
Specify how initial listing should be handled. Used by 'Tracking Entities' strategy.

Relationships:

NameDescription
successAll FlowFiles that are received are routed to success

Reads Attributes:

None specified.

Writes Attributes:

NameDescription
azure.filesystemThe name of the Azure File System
azure.filePathThe full path of the Azure File
azure.directoryThe name of the Azure Directory
azure.filenameThe name of the Azure File
azure.lengthThe length of the Azure File
azure.lastModifiedThe last modification time of the Azure File
azure.etagThe ETag of the Azure File

State management:

ScopeDescription
CLUSTERAfter performing a listing of files, the timestamp of the newest file is stored. This allows the Processor to list only files that have been added or modified after this date the next time that the Processor is run. State is stored across the cluster so that this Processor can be run on Primary Node only and if a new Primary Node is selected, the new node can pick up where the previous node left off, without duplicating the data.

Restricted:

This component is not restricted.

Input requirement:

This component does not allow an incoming relationship.

System Resource Considerations:

None specified.

See Also:

PutAzureDataLakeStorage, DeleteAzureDataLakeStorage, FetchAzureDataLakeStorage