Splunk® Data Stream Processor

Function Reference

Acrobat logo Download manual as PDF

Acrobat logo Download topic as PDF

Write thru KV Store

This topic describes how to use the function in the Splunk Data Stream Processor.

Description

Writes data to a KV store collection that you specify. In the SPL2 Builder, this function must be used directly after thru.

To use this function, you must first connect to a Splunk Enterprise KV Store. See Connect DSP to a Splunk Enterprise KV Store.

Because this function is a passthrough (thru) function, it cannot be the last function in the pipeline. If it is the last function in the pipeline, then the pipeline fails to validate with error "Sink dataset [kvstore_lookup_sink] does not exist in registry".

Syntax

The required syntax is in bold.

kvstore_lookup_sink <lookup_dataset>
predicate:<boolean-expression>
lookup_fields:<fields>...
event_fields:<fields>...
mode=replace | append

Required arguments

lookup_dataset
Syntax: <string>
Description: The name of the connection to your KV Store collection. Before using this function, you must connect to a Splunk Enterprise KV Store. See Connect DSP to a Splunk Enterprise KV Store.
Example: my_kvstore_lookup
predicate
Syntax: expression<boolean>
Description: An SPL2 expression that returns a Boolean value. Data is written to the KV Store when the predicate evaluates to true. See Predicates in the Search Manual.
Example: isnotnull(timestamp)
lookup_fields
Syntax: <fields>
Description: The field names in the KV Store to match to the field names in the incoming records. The arguments lookup_fields and event_fields must contain the same number of entries and be in the same order for proper matching. If you are using the replace mode, you must explicitly specify the _key field since that is the primary key in Splunk Enterprise KV collection datasets.
Example: _key, date, source
event_fields
Syntax: <fields>
Description: The field names in the incoming records to match to the field names in the KV Store. The arguments lookup_fields and event_fields must contain the same number of entries and be in the same order for proper matching.
Example: id, timestamp, source

Optional arguments

mode
Syntax: replace or append
Description: Choose a mode to specify how DSP writes data to the KV Store.
Example: append
Write mode Description
replace In replace mode, incoming data from DSP replaces existing data in the KV Store collection using a defined primary key. The function takes two lists of the same length, lookup_fields and event_fields. event_fields contains field names of the incoming event, and lookup_fields contains the corresponding field names to update in the collection. One of the lookup_fields must be _key, and the corresponding field name in event_fields designates the primary key used to match records. See the SPL2 example below.

In replace mode, since you are overwriting rows in the database with the specified _key, a single version of the row will exist in the table, making it easy to see the most recent data.

append In append mode, since the primary key field _key is auto-generated, incoming data from DSP is appended to the designated KV Store. The KV Store's existing rows are not updated.

Usage

This section contains additional usage information about the Write Thru KV Store function.

Previewing the Write thru KV Store function

Because this function does not do any transformations on incoming streaming data, this function shows the same preview results as the function preceding it.

Performing lookups on large KV stores

When your KV Store collection is extremely large, performance can suffer when your lookups must search through the entire collection to retrieve matching field values. When you are writing data to a Splunk Enterprise KV Store, be mindful of your collection size and growth. If you are seeing performance issues on your lookup function, then your Splunk Enterprise KV Store collection might be reaching capacity and you might need to manually delete old entries from the collection. See Use the REST API to manage KV Store collections and data for information on how to delete records from a collection.

SPL2 examples

1. Replace data in a KV Store collection with data from DSP

This example writes incoming streaming data to the lookup dataset mylookupdataset.

...| thru kvstore_lookup_sink(lookup_dataset: "mylookupdataset", predicate: not(isnull('productId')), mode:"replace", lookup_fields: ["_key", "productId", "product_name", "price"], event_fields: ["id", "productId", "body", "sale_price"]);

Suppose your KV Store collection contains the following data:

_key productId product_name price
5f3f5454d240a1300236fec1 DB-SG-G01 Mediocre Kingdoms 24.99
5f3f5454d240a1300236fec2 DC-SG-G02 Dream Crusher 39.99
5f3f5454d240a1300236fec3 WC-SH-G04 World of Cheese 19.99

The incoming DSP records look something like this:

id productId body sale_price
5f3f5454d240a1300236fec1 DB-SG-G01 Mediocre Kingdoms 19.99
5f3f5454d240a1300236fec2 DB-SG-G02 Dream Crusher 14.99
5f3f5454d240a1300236fec3 DB-SG-G03 World of Cheese 9.99

After configuring the Write Thru KV Store function, the data in the KV Store collection is updated with data from DSP.

_key productId product_name price
5f3f5454d240a1300236fec1 DB-SG-G01 Mediocre Kingdoms 19.99
5f3f5454d240a1300236fec2 DB-SG-G02 Dream Crusher 14.99
5f3f5454d240a1300236fec3 DB-SG-G03 World of Cheese 9.99

2. Add data from DSP to the KV Store collection

This example writes incoming streaming data to the lookup dataset mylookupdataset.

...| thru kvstore_lookup_sink(lookup_dataset: "mylookupdataset", predicate: not(isnull(productId)), mode:"append", lookup_fields: ["productId", "product_name", "price"], event_fields: ["productId", "body", "sale_price"]);


Suppose your KV Store collection contains the following data:

_key productId product_name price
5f3f5454d240a1300236fec1 DB-SG-G01 Mediocre Kingdoms 24.99
5f3f5454d240a1300236fec2 DC-SG-G02 Dream Crusher 39.99
5f3f5454d240a1300236fec3 WC-SH-G04 World of Cheese 19.99

The incoming DSP records look something like this:

id productId body sale_price
2518594268716256 EW-SG-G04 Escape from Waterworld 35.00
2518594268716257 FT-SG-G05 Farm Town 19.99
2518594268716258 DB-SG-G06 Puzzle Solver 4.99

After configuring the Write Thru KV Store function, the data in the KV Store collection is now enriched with the incoming streaming data. Note that since _key was not present in DSP, the KV Store generated a primary key (_key) value. In addition, even though id was a field in DSP, it was not written to the KV Store collection because it wasn't specified in the event_fields argument.

_key productId product_name price
5f3f5454d240a1300236fec1 DB-SG-G01 Mediocre Kingdoms 24.99
5f3f5454d240a1300236fec2 DC-SG-G02 Dream Crusher 39.99
5f3f5454d240a1300236fec3 WC-SH-G04 World of Cheese 19.99
5f3f5454d240a1300236fec4 EW-SG-G04 Escape from Waterworld 35.00
5f3f5454d240a1300236fec5 FT-SG-G05 Farm Town 19.99
5f3f5454d240a1300236fec6 DB-SG-G06 Puzzle Solver 4.99
Last modified on 30 October, 2020
PREVIOUS
Thru
  NEXT
Get data from Splunk DSP Firehose

This documentation applies to the following versions of Splunk® Data Stream Processor: 1.2.0


Was this documentation topic helpful?

You must be logged into splunk.com in order to post comments. Log in now.

Please try to keep this discussion focused on the content covered in this documentation topic. If you have a more general question about Splunk functionality or are experiencing a difficulty with Splunk, consider posting a question to Splunkbase Answers.

0 out of 1000 Characters