Luigi De Masi created CAMEL-23776:
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Summary: camel-a2a: Add a2aSubTask YAML route step for scoped
progress events
Key: CAMEL-23776
URL: https://issues.apache.org/jira/browse/CAMEL-23776
Project: Camel
Issue Type: Improvement
Environment: CAMEL-23063 introduces A2A progress event emission from
Camel routes through the Simple language function:
${a2a:emit('Searching docs...')}
This allows route authors to emit progress updates, but common use cases
require several explicit route steps around the actual work being performed.
For example, a route may need to
emit a progress event before a search, another event after the search
succeeds, and another event if the search fails.
This improvement proposes adding an `a2aSubTask` YAML route step in camel-a2a.
The `a2aSubTask` step should group one or more nested Camel route steps and
emit A2A progress events around that grouped work.
Example:
{code:yaml}
steps:
- a2aSubTask:
emitBefore: "Searching docs..."
emitAfter: "Docs found: ${body.size()}"
emitOnError: "Error searching docs: ${exception.message}"
steps:
- to:
uri: elasticsearch:docs?operation=Search
- a2aSubTask:
emitBefore: "Drafting answer..."
emitAfter: "Answer drafted: ${body}"
emitOnError: "Error drafting answer: ${exception.message}"
steps:
- bean:
ref: answerDraftingService
method: draft
- setBody:
simple: "Final answer: ${body}"
{code}
The emitted messages should support Simple expressions and should be
evaluated against the current Exchange at the time each event is emitted.
Expected behavior:
* `emitBefore` is evaluated and emitted before the nested steps are executed.
* `emitAfter` is evaluated and emitted after the nested steps complete
successfully.
* `emitOnError` is evaluated and emitted when the nested steps throw an
exception.
* `emitOnError` must not swallow, replace, or hide the original exception.
* All emit fields are optional.
* The step should support one or more nested Camel route steps.
* The nested steps should behave like normal route steps.
* Existing `${a2a:emit(...)}` support remains available and unchanged.
Implementation notes:
* This issue should add the A2A-specific route model/reifier/processor
support needed by `a2aSubTask`.
* The YAML parser integration should use the generic YAML DSL extension
mechanism tracked separately.
* The YAML DSL core should not hard-code the `a2aSubTask` step.
Non-goals:
* This issue should not implement the generic YAML DSL extension mechanism.
* This issue should not add Java DSL or XML DSL syntax for `a2aSubTask`.
* This issue should not change existing A2A progress emission semantics.
* This issue should not replace the existing `${a2a:emit(...)}` Simple
function.
* This issue should not introduce retry, cancellation, aggregation, or task
lifecycle behavior.
Acceptance criteria:
* `camel-a2a` provides an `a2aSubTask` YAML route step.
* `a2aSubTask` supports nested `steps`.
* `emitBefore`, `emitAfter`, and `emitOnError` are optional.
* Emit message templates are evaluated as Simple expressions.
* `emitOnError` can access the exception through `${exception.message}`.
* Exceptions from nested steps continue to propagate normally.
* Tests cover successful execution, failure execution, no emit fields, only
one emit field, and multiple nested steps.
* Documentation includes the new YAML syntax and at least one full route
example.
Reporter: Luigi De Masi
Assignee: Luigi De Masi
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