feat(nexus): add async, cancellation, failure and parallel features by xepozz · Pull Request #871 · temporalio/features

xepozz · 2026-08-19T06:11:22Z

Four Nexus scenarios implemented in Go and Java: an async workflow-run operation, cancelling a running async operation, a sync operation that fails with an application error, and three parallel sync operations.

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Four Nexus scenarios implemented in Go and Java: an async workflow-run operation, cancelling a running async operation, a sync operation that fails with an application error, and three parallel sync operations.

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chatgpt-codex-connector · 2026-08-19T06:15:37Z

+		}
+		return runner.Client.ExecuteWorkflow(ctx, opts, Workflow, runner.NexusEndpoint)
+	},
+	CheckHistory: func(ctx context.Context, runner *harness.Runner, run client.WorkflowRun) error {


Preserve default replay in Go history checks

When this feature runs, assigning CheckHistory replaces the harness path that calls Runner.CheckHistoryDefault (harness/go/harness/runner.go lines 151-157), so neither the current executions—including the backing workflow—nor stored histories are replayed. Run the default checker after the event assertion; the same omission occurs in the other three newly added Go Nexus features.

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chatgpt-codex-connector · 2026-08-19T06:15:37Z

+    }
+
+    @Override
+    public void checkHistory(Runner runner, Run run) throws Exception {


Preserve default replay in Java history checks

Overriding checkHistory here bypasses the default implementation in Feature.java, which calls runner.checkCurrentAndPastHistories(run). Consequently this feature never replay-checks its caller or backing workflow and cannot detect compatibility regressions against saved histories; invoke the default replay helper after the custom assertion. The other three new Java Nexus features have the same omission.

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chatgpt-codex-connector · 2026-08-19T06:15:37Z

+                    .getResult()
+                    .handle(
+                        (value, failure) -> {
+                          resultHolder[0] = failure == null ? "completed" : "cancelled";


Verify that the operation actually reports cancellation

When the operation result fails for any reason after scope.cancel()—for example a timeout or backing-workflow application failure—this callback labels it "cancelled", and the workflow plus history assertion still pass. Since the feature specifically promises to observe a cancellation error, inspect the failure chain for CanceledFailure rather than treating every non-null failure as cancellation.

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This is a good flag, in the Go test we do check for this already

The java handler threw a bare application failure, which the SDK reports as a handler error, so the two languages were asserting different contracts.

Quinn-With-Two-Ns · 2026-08-21T15:24:31Z

+              .build();
+      TestService stub = Workflow.newNexusServiceStub(TestService.class, serviceOptions);
+
+      var resultHolder = new String[1];


Suggested change

var resultHolder = new String[1];

var resultHolder = Workflow.newPromise();

Quinn-With-Two-Ns · 2026-08-21T15:27:59Z

+      return OperationHandler.sync(
+          (context, details, name) -> {
+            throw OperationException.failure(
+                ApplicationFailure.newNonRetryableFailure("deliberate failure", "TestError"));


In the Go test temporal.NewApplicationError(ErrorMessage, ErrorType) this will return a retry able application error

The two tests should be consistent

Quinn-With-Two-Ns · 2026-08-21T15:30:39Z

@@ -0,0 +1,13 @@
+# Nexus sync operation fails
+
+A workflow invokes a synchronous Nexus operation that raises an application failure and


The Nexus operations you wrote do not "raises an application failure", they raise a OperationError. The OperationError happens to contain a application failure as a cause but from the SDKs perspective that is not relevant. What you have tested is fine, but I would correct the spec.

I'll note having a test where the Nexus operation DOES raise a application failure would also be a good test, but it doesn't have to be in this PR

Quinn-With-Two-Ns · 2026-08-21T15:31:30Z

@@ -0,0 +1,12 @@
+# Nexus operations run in parallel
+
+A workflow starts three synchronous Nexus operations in a single workflow task and awaits all


Can you please change the folder name to clarify this is parallel sync operations.

Keep the default history replay: the CheckHistory and checkHistory overrides now call CheckHistoryDefault and checkCurrentAndPastHistories, which the harness skips entirely when a feature supplies its own checker. Assert the contracts the features claim instead of proxies for them: the java caller looks for CanceledFailure in the cause chain rather than treating any failure as cancellation, both languages assert the NexusOperationCanceled event, and the parallel feature asserts that all three operations are scheduled by a single workflow task. Look up the application error by type rather than by cause-chain depth in both languages, and fail with a diagnostic when it is missing. Raise a retryable application error from the java handler so it matches the go one, and share the type and message through constants. Rename parallel_operations to parallel_sync_operations, align the workflow results and error type between go and java, use CompletablePromise instead of a mutable array in the java caller, and correct the sync_operation_error spec: the handler raises an operation error that carries an application error as its cause, not an application error directly. nexus/sync_success gets the same replay fix so the whole nexus family behaves alike; it is the only change outside the original diff of this PR.

feat(nexus): add async, cancellation, failure and parallel features

d5d438c

Four Nexus scenarios implemented in Go and Java: an async workflow-run operation, cancelling a running async operation, a sync operation that fails with an application error, and three parallel sync operations.

xepozz requested review from a team as code owners August 19, 2026 06:11

chatgpt-codex-connector Bot reviewed Aug 19, 2026

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fix(nexus): raise an operation error in the java failure feature

8e0324e

The java handler threw a bare application failure, which the SDK reports as a handler error, so the two languages were asserting different contracts.

Quinn-With-Two-Ns reviewed Aug 21, 2026

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Quinn-With-Two-Ns approved these changes Aug 23, 2026

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feat(nexus): add async, cancellation, failure and parallel features - #871

feat(nexus): add async, cancellation, failure and parallel features#871
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	var resultHolder = new String[1];
	var resultHolder = Workflow.newPromise();

		@@ -0,0 +1,13 @@
		# Nexus sync operation fails

		A workflow invokes a synchronous Nexus operation that raises an application failure and

		@@ -0,0 +1,12 @@
		# Nexus operations run in parallel

		A workflow starts three synchronous Nexus operations in a single workflow task and awaits all

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xepozz commented Aug 19, 2026

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