Filter Node
Quick Reference
- Filter: A FEEL expression that evaluates to boolean. Records where the expression returns
truepass through; others are dropped.
Configuration
Configuration keys below are relative to the node configuration. Use the field name in the panel when following instructions in the builder; required markers such as an asterisk are not part of the name.
| Field in the panel | Configuration key | Where to edit / when shown |
|---|---|---|
| Filter | expression | Node panel — A FEEL expression that evaluates to boolean. Records where the expression returns true pass through; others are dropped. Required: Yes. Placeholder: $.events. |
Relational comparisons (<, <=, >, >=) return null when either operand is null, including a missing field. For example, if the record has no severity field, $.severity >= 3 returns null, not false. Filter drops that record because only boolean true passes. This is different from an equality check such as $.severity == null, which returns true for that missing field.
Overview
The filter node allows you to selectively process records in your ZephFlow pipeline based on specific conditions. It evaluates each incoming record against an expression written in the Fleak Eval Expression Language (FEEL). Records that evaluate to true are passed to downstream nodes; otherwise, they are dropped from the pipeline.
Examples
In FEEL expressions, $ refers to the current record. Use dot-path notation (e.g. $.field) to access fields.
Relational comparisons (<, <=, >, >=) return null when either operand is null, including a missing field. For example, if the record has no severity field, $.severity >= 3 returns null, not false. Filter drops that record because only boolean true passes. This is different from an equality check such as $.severity == null, which returns true for that missing field.
Keep only error records:
$.level == "ERROR"
Filter by numeric threshold:
$.amount > 100 and $.status == "completed"
Check field existence:
$.email != null
Related nodes
- eval: Transform records using the same expression language