Template Reference

Templates let you generate dynamic subjects, headers, and payloads. Use them when static text is not enough.

Template Syntax

Use \{\{ ... \}\} expressions:

spec:
  subject:
    fromString: "orders.{{ msg_count() }}"
    parseAsTemplate: true

Functions are namespaced, for example:

• uuid.v4()
• time.rfc3339()
• strings.toUpper("abc")

Common Recipes

Correlation ID per message

headers:
  - key: X-Correlation-Id
    value: "{{ uuid.v7() }}"

Timestamp in payload

data:
  fromString: '{"sentAt":"{{ time.rfc3339() }}"}'
  parseAsTemplate: true

Subject with sequence number

subject:
  fromString: "orders.created.{{ msg_count() }}"
  parseAsTemplate: true

Randomized test data

data:
  fromString: '{"name":"{{ rand.person.firstName() }}","email":"{{ rand.person.email() }}"}'
  parseAsTemplate: true

Base64 encode payload field

data:
  fromString: '{"token":"{{ encode.base64(uuid.v4()) }}"}'
  parseAsTemplate: true

Runtime Variables

Variable	Available In	Description
msg_count()	subject, headers, data	1-based index of the current message/request iteration
msg_subject()	headers, data	The resolved subject of the current message

Where Templates Are Evaluated

Field	Flag	Default
spec.subject.fromString (Publish/Request)	parseAsTemplate	false
spec.data.fromString and spec.data.fromFile	parseAsTemplate	true when omitted
spec.headers[].key	parseKeyAsTemplate	true
spec.headers[].value	parseValueAsTemplate	true

If you need literal \{\{ ... \}\} text, disable parsing with the matching flag.

High-Value Namespaces

• uuid: request IDs and correlation keys
• time: timestamps and date partitioning
• rand: sample payload generation
• strings: formatting and normalization
• encode / hash: signing, encoding, and checksums

Troubleshooting

• Template not evaluated: check parse flags (parseAsTemplate, parseValueAsTemplate, etc.)
• Unknown function: verify namespace (for example uuid.v4() not uuid_v4())
• File templates: fromFile paths are relative to the collection directory
• Prefer smaller templates and keep complex payloads in files for readability