SampleRecord

Description:

Samples the records of a FlowFile based on a specified sampling strategy (such as Reservoir Sampling). The resulting FlowFile may be of a fixed number of records (in the case of reservoir-based algorithms) or some subset of the total number of records (in the case of probabilistic sampling), or a deterministic number of records (in the case of interval sampling).

Additional Details...

Tags:

record, sample, reservoir, range, interval

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.

Display NameAPI NameDefault ValueAllowable ValuesDescription
Record Readerrecord-readerController Service API:
RecordReaderFactory
Implementations: CEFReader
Syslog5424Reader
ScriptedReader
SyslogReader
CSVReader
GrokReader
JsonTreeReader
XMLReader
AvroReader
ReaderLookup
WindowsEventLogReader
ParquetReader
JsonPathReader
Specifies the Controller Service to use for parsing incoming data and determining the data's schema
Record Writerrecord-writerController Service API:
RecordSetWriterFactory
Implementations: RecordSetWriterLookup
XMLRecordSetWriter
FreeFormTextRecordSetWriter
CSVRecordSetWriter
ScriptedRecordSetWriter
AvroRecordSetWriter
JsonRecordSetWriter
ParquetRecordSetWriter
Specifies the Controller Service to use for writing results to a FlowFile
Sampling Strategysample-record-sampling-strategyReservoir Sampling
  • Interval Sampling Selects every Nth record where N is the value of the 'Interval Value' property
  • Range Sampling Creates a sample of records based on the index (i.e. record number) of the records using the specified range. An example is '3,6-8,20-' which includes the third record, the sixth, seventh and eighth record, and all records from the twentieth record on. Commas separate intervals that don't overlap, and an interval can be between two numbers (i.e. 6-8) or up to a given number (i.e. -5), or from a number to the number of the last record (i.e. 20-).
  • Probabilistic Sampling Selects each record with probability P where P is the value of the 'Selection Probability' property
  • Reservoir Sampling Creates a sample of K records where each record has equal probability of being included, where K is the value of the 'Reservoir Size' property. Note that if the value is very large it may cause memory issues as the reservoir is kept in-memory.
Specifies which method to use for sampling records from the incoming FlowFile
Sampling Intervalsample-record-intervalSpecifies the number of records to skip before writing a record to the outgoing FlowFile. This property is only used if Sampling Strategy is set to Interval Sampling. A value of zero (0) will cause no records to be included in theoutgoing FlowFile, a value of one (1) will cause all records to be included, and a value of two (2) will cause half the records to be included, and so on.
Supports Expression Language: true (will be evaluated using flow file attributes and variable registry)

This Property is only considered if the [Sampling Strategy] Property has a value of "Interval Sampling".
Sampling Rangesample-record-rangeSpecifies the range of records to include in the sample, from 1 to the total number of records. An example is '3,6-8,20-' which includes the third record, the sixth, seventh and eighth records, and all records from the twentieth record on. Commas separate intervals that don't overlap, and an interval can be between two numbers (i.e. 6-8) or up to a given number (i.e. -5), or from a number to the number of the last record (i.e. 20-). If this property is unset, all records will be included.
Supports Expression Language: true (will be evaluated using flow file attributes and variable registry)

This Property is only considered if the [Sampling Strategy] Property has a value of "Range Sampling".
Sampling Probabilitysample-record-probabilitySpecifies the probability (as a percent from 0-100) of a record being included in the outgoing FlowFile. This property is only used if Sampling Strategy is set to Probabilistic Sampling. A value of zero (0) will cause no records to be included in theoutgoing FlowFile, and a value of 100 will cause all records to be included in the outgoing FlowFile..
Supports Expression Language: true (will be evaluated using flow file attributes and variable registry)

This Property is only considered if the [Sampling Strategy] Property has a value of "Probabilistic Sampling".
Reservoir Sizesample-record-reservoirSpecifies the number of records to write to the outgoing FlowFile. This property is only used if Sampling Strategy is set to reservoir-based strategies such as Reservoir Sampling.
Supports Expression Language: true (will be evaluated using flow file attributes and variable registry)

This Property is only considered if the [Sampling Strategy] Property has a value of "Reservoir Sampling".
Random Seedsample-record-random-seedSpecifies a particular number to use as the seed for the random number generator (used by probabilistic strategies). Setting this property will ensure the same records are selected even when using probabilistic strategies.
Supports Expression Language: true (will be evaluated using flow file attributes and variable registry)

This Property is only considered if the [Sampling Strategy] Property is set to one of the following values: [Probabilistic Sampling], [Reservoir Sampling]

Relationships:

NameDescription
successThe FlowFile is routed to this relationship if the sampling completed successfully
failureIf a FlowFile fails processing for any reason (for example, any record is not valid), the original FlowFile will be routed to this relationship
originalThe original FlowFile is routed to this relationship if sampling is successful

Reads Attributes:

None specified.

Writes Attributes:

NameDescription
mime.typeThe MIME type indicated by the record writer
record.countThe number of records in the resulting flow file

State management:

This component does not store state.

Restricted:

This component is not restricted.

Input requirement:

This component requires an incoming relationship.

System Resource Considerations:

ResourceDescription
MEMORYAn instance of this component can cause high usage of this system resource. Multiple instances or high concurrency settings may result a degradation of performance.