WF-IMPL-077: DaprActivityRuntimeClient.cancel_activity adapter

[toddysm]

Summary

Closes #488. Implements the production DaprActivityRuntimeClient.cancel_activity HTTP adapter against the local Dapr sidecar's Service Invocation API. Cancellation is idempotent end-to-end: 404 (ARM has no record) and 409 (already terminated) collapse to a silent no-op with an INFO-level breadcrumb so operators can trace the cancel without it looking like an error.

Changes

Source — src/services/workflow-service/src/custos_workflow/clients/activity_runtime.py

• New constant CANCEL_ACTIVITY_DAPR_METHOD = "CancelActivity" (exported via __all__).
• Module-level _LOGGER = logging.getLogger(__name__) for the cancel-path INFO breadcrumbs.
• DaprActivityRuntimeClient.cancel_activity replaces the WF-IMPL-076 NotImplementedError placeholder with an async POST that:
  • 200 / 204 → return.
  • 404 → INFO log + return (ARM has no record of the step).
  • 409 → INFO log + return (ARM reports step already terminated).
  • Any other 4xx or 5xx → raise OutboundRpcStatusError with the observed status_code so RunController can surface it via RunControllerError.
  • httpx.HTTPError → raise OutboundRpcTransportError, with the underlying httpx exception preserved on __cause__.
• No envelope mapping: cancel_activity returns None per the Protocol surface; callers distinguish success from failure by whether an exception escapes.
• No Idempotency-Key header: cancellation is idempotent on ARM via 404/409, so retries are byte-identical without keying. This is asserted in the test suite.
• Updated DaprActivityRuntimeClient docstring to reflect that both methods are now async.

Tests — tests/clients/test_dapr_activity_runtime.py

17 new tests covering the full status-code matrix:

• 200 / 204 success returns None.
• 404 idempotent no-op + caplog-asserted INFO breadcrumb with run_id / step_id extras.
• 409 idempotent no-op + caplog-asserted INFO breadcrumb.
• 400 / 401 / 403 / 422 raise OutboundRpcStatusError with status_code echoed.
• 500 / 502 / 503 / 504 raise OutboundRpcStatusError with status_code echoed.
• httpx.ConnectTimeout and httpx.ConnectError raise OutboundRpcTransportError; original exception preserved on __cause__.
• URL targets /v1.0/invoke/<arm-app-id>/method/CancelActivity (not ScheduleActivity).
• Body uses camelCase: {"runId": ..., "stepId": ...}.
• No Idempotency-Key header is attached (asserted via case-insensitive header set diff).
• Per-call timeout propagates to req.extensions["timeout"].

Quality

• ruff check / ruff format --check clean.
• mypy --strict clean (158 source files).
• 1802 passed, 1 pre-existing flake (tests/test_observability.py::test_module_imports_under_noop_providers).
• activity_runtime.py: 100 % coverage; full-suite 98.97 %.

Design references

• Workflow service: design/components/workflow-service/design.md § Internal RPC outbound — CancelActivity.
• ARM: design/components/activity-runtime-manager/design.md § Internal RPCs.
• Protocol contract: ActivityRuntimeClient.cancel_activity (idempotency contract).

Tracker

• WF-IMPL-000-ARM-CONNECTOR-ADAPTERS (WF-IMPL-000-ARM-CONNECTOR-ADAPTERS: workflow-service Real ARM Client + Connector Client adapters implementation tracker #495).

[Copilot]

Pull request overview

Implements the production DaprActivityRuntimeClient.cancel_activity adapter in workflow-service, calling ARM via the local Dapr sidecar’s Service Invocation API and enforcing the idempotent cancellation contract (404/409 treated as no-ops).

Changes:

• Added CANCEL_ACTIVITY_DAPR_METHOD and implemented DaprActivityRuntimeClient.cancel_activity as an async HTTP POST with the specified status/transport error taxonomy and INFO breadcrumbs for idempotent no-ops.
• Expanded the test_dapr_activity_runtime suite to cover the cancel status-code matrix, wire shape (URL + camelCase body), timeout propagation, and header invariants (no Idempotency-Key for cancel).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/services/workflow-service/src/custos_workflow/clients/activity_runtime.py	Adds CancelActivity method constant + logger and implements the cancel adapter with idempotent 404/409 handling and error mapping.
src/services/workflow-service/tests/clients/test_dapr_activity_runtime.py	Adds comprehensive unit tests for cancel_activity behavior, including logging breadcrumbs, wire contract, and error taxonomy.

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