Add large payload support

[bachuv]

Issue describing the changes in this PR

Adding large payload support in the Java SDK.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes are added to the CHANGELOG.md
• I have added all required tests (Unit tests, E2E tests)

Additional information

Additional PR information

[Copilot]

Pull request overview

Adds large payload support to the Durable Task Java SDK by introducing an external payload store abstraction, wiring it into client/worker/runner execution paths, and providing an Azure Blob Storage-backed implementation for Azure Functions scenarios.

Changes:

• Introduces PayloadStore, LargePayloadOptions, and internal helpers to externalize/resolve payloads in protobuf messages.
• Updates worker/client/orchestration runner to resolve incoming tokens and externalize outgoing large payloads; adds orchestrator response chunking.
• Adds new azure-blob-payloads module with BlobPayloadStore + options, and wires it into the Azure Functions middleware.

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
settings.gradle	Registers the new :azure-blob-payloads Gradle module.
client/src/main/java/com/microsoft/durabletask/PayloadStore.java	Public interface for upload/download + token recognition.
client/src/main/java/com/microsoft/durabletask/LargePayloadOptions.java	Configures externalization thresholds and max externalized payload size.
client/src/main/java/com/microsoft/durabletask/PayloadHelper.java	Centralizes size checks + store delegation for externalize/resolve.
client/src/main/java/com/microsoft/durabletask/PayloadInterceptionHelper.java	Resolves/externalizes payload fields inside orchestration/activity protobufs.
client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcWorkerBuilder.java	Adds externalized payload configuration + response chunk-size configuration.
client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcWorker.java	Resolves incoming tokens, externalizes outputs, announces capability, and chunks orchestrator responses.
client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcClientBuilder.java	Adds externalized payload configuration for the client.
client/src/main/java/com/microsoft/durabletask/DurableTaskGrpcClient.java	Externalizes outgoing inputs/reasons and resolves tokens in returned metadata.
client/src/main/java/com/microsoft/durabletask/OrchestrationRunner.java	Adds overloads to run orchestrations with externalized payload support.
client/src/test/java/com/microsoft/durabletask/PayloadHelperTest.java	Unit tests for thresholding, max cap behavior, and resolve/externalize round trips.
client/src/test/java/com/microsoft/durabletask/PayloadInterceptionHelperTest.java	Unit tests verifying request/response interception resolves/externalizes expected fields.
client/src/test/java/com/microsoft/durabletask/LargePayloadOptionsTest.java	Unit tests for defaults and validation behavior.
client/src/test/java/com/microsoft/durabletask/OrchestrationRunnerPayloadTest.java	Tests runner load+run behavior with/without a store.
client/src/test/java/com/microsoft/durabletask/DurableTaskGrpcWorkerBuilderTest.java	Tests chunk-size validation and externalized payload builder configuration.
client/src/test/java/com/microsoft/durabletask/LargePayloadIntegrationTests.java	End-to-end integration tests for externalization + autochunk behavior.
client/build.gradle	Makes test Java executable selection Windows-aware.
azurefunctions/src/main/java/.../OrchestrationMiddleware.java	Initializes a blob-backed payload store from env vars and passes it to the runner.
azurefunctions/build.gradle	Adds dependency on the new :azure-blob-payloads module.
azure-blob-payloads/build.gradle	New module build + publish/sign/spotbugs configuration.
azure-blob-payloads/src/main/java/.../BlobPayloadStoreOptions.java	Config object for blob-based payload storage.
azure-blob-payloads/src/main/java/.../BlobPayloadStore.java	Azure Blob-backed PayloadStore implementation with optional gzip.
azure-blob-payloads/src/main/java/.../AzureBlobPayloadsExtensions.java	Convenience methods to configure builders with blob payload storage.
azure-blob-payloads/src/test/java/.../BlobPayloadStoreOptionsTest.java	Unit tests for options validation and defaults.
azure-blob-payloads/spotbugs-exclude.xml	SpotBugs exclusions for exposed Azure SDK client objects in options.

[YunchuWang]

Code Review: Large Payload Support

Good overall design — the PayloadStore abstraction, PayloadHelper threshold logic, and PayloadInterceptionHelper protobuf interception are well-structured. The response chunking implementation is solid. However, I found several issues that need attention.

Summary of Findings

Critical:

1. OrchestrationMiddleware silently enables blob storage for ALL Azure Functions apps (falls back to AzureWebJobsStorage)
2. OrchestrationMiddleware hardcodes BlobPayloadStore — violates the PayloadStore abstraction

Medium (Performance):
3. BlobPayloadStore.upload() makes 2 HTTP calls for compressed uploads (upload + setHttpHeaders)
4. BlobPayloadStore.download() makes 2 HTTP calls (downloadStream + getProperties)
5. PayloadHelper.maybeExternalize() allocates full UTF-8 byte array just to check size

Low / Design:
6. BlobPayloadStore.extractBlobName() ignores container name from token
7. PayloadStore interface has no delete() — externalized payloads accumulate forever
8. PayloadInterceptionHelper — field.isInitialized() is always true in proto3
9. BlobPayloadStore constructor makes network call (ensureContainerExists)