Reverse

Mutate

Synopsis

Reverses the order of a field's contents: the characters of a string, or the elements of an array.

Schema

- reverse:
    field: <ident>
    description: <text>
    if: <script>
    ignore_failure: <boolean>
    ignore_missing: <boolean>
    on_failure: <processor[]>
    on_success: <processor[]>
    tag: <string>
    target_field: <ident>

Configuration

The following fields are used to define the processor:

Field	Required	Default	Description
field	Y	-	Field to reverse. Must hold a string or an array
description	N	-	Explanatory note
if	N	-	Condition to run
ignore_failure	N	false	See Handling Failures
ignore_missing	N	false	If true, quietly exit if field doesn't exist
on_failure	N	-	See Handling Failures
on_success	N	-	See Handling Success
tag	N	-	Identifier
disabled	N	false	When true, the processor is skipped and the event continues to the next one. Lets you take a processor out of the path without removing its configuration
target_field	N	field	Field to store the reversed value. Defaults to field, reversing in place

Details

A string is reversed by character, not by byte, so multi-byte text survives the operation intact. An array is reversed by element; the elements themselves are untouched, including nested objects and arrays.

Any other value — a number, an object, a boolean — is an error. There is no meaningful element order to reverse.

The reversed value is built as a new value rather than being rearranged in place, so a target_field that differs from field leaves the source exactly as it was.

Examples

Reversing a String

Reversing the characters of a string...	{ "domain": "example.com" } - reverse: field: domain target_field: domain_reversed
which is the form domain lookups often index on:	{ "domain": "example.com", "domain_reversed": "moc.elpmaxe" }

Reversing an Array

Reversing element order, newest event first...	{ "trace": ["dispatch", "validate", "receive"] } - reverse: field: trace
in place, since no target_field was given:	{ "trace": ["receive", "validate", "dispatch"] }

Non-ASCII Text

Reversal is by character, so accented and non-Latin text is not corrupted...	{ "label": "café" } - reverse: field: label target_field: label_reversed
and the accented character survives:	{ "label": "café", "label_reversed": "éfac" }