Upload oversized outbound Avro payloads through the namespace runtime

[rmcdaniel]

Evidence

The shared Rust request path in src/lib.rs still serializes the original body with request.json(body). src/runtime_payloads.rs implements response reference resolution and authenticated GET downloads, but no outbound upload/discovery path. This leaves the Rust SDK unable to submit values above the ordinary Server request limit even when the namespace advertises runtime-owned external payload storage. This is the Rust counterpart of durable-workflow/sdk-php#63, not a codec change. Source-confirmed gap; a native Rust reproduction remains required.

Required outcome

• Discover the namespace inline threshold, transport byte limit and availability; upload encoded Avro wire blobs through the authenticated namespace runtime, not provider credentials or URIs.
• Preserve worker/client role, namespace, checksum, exact byte size and content-addressed retry identity. Use bounded responses, timeouts and no redirects.
• Cover client and worker payload positions, including batches that exceed the ordinary JSON request limit, without interpreting arbitrary application maps as protocol metadata.
• Preserve typed Rust payload fidelity and existing inbound limits; reject unsupported or over-limit values meaningfully before sending an oversized ordinary request.
• Qualify against a published Server with a clean installed consumer, above-threshold workflow input, activity arguments/result, workflow result, exact transport maximum, and cold runtime/worker restart. Include focused failure, integrity, namespace and role tests.

Finish PHP SDK #63 and its Server protocol qualification first, then implement this parity work before claiming the external-payload path is complete across first-party SDKs.

[rmcdaniel]

Native reproduction is now confirmed with the released crate, not only source inspection.

A clean Cargo consumer installed durable-workflow = 2.0.3 on Rust 1.86.0 and connected to a disposable native Apache Server 2.3.3 / Workflow 2.0.7 / MySQL 8.0.46 fixture. It used the namespace operator credential. cluster_info() explicitly reported storage available, inline threshold 64 bytes, and transport maximum 67,108,864 bytes. Starting external-payload.proof with a 3,014,656-byte string via Client::start_workflow returned HTTP 413 payload_too_large, ordinary limit 2,097,152 bytes. No upload occurred through the shared request_json path. The same authored workflow and payload just passed with released PHP SDK 2.0.8 against this exact runtime.

Server image index: sha256:8bab27213a1a10740af9dd32f716b510d3c85a8b3eeeec197c6611aef06ce73e. Rust toolchain image: rust:1.86-bookworm at sha256:300ec56abce8cc9448ddea2172747d048ed902a3090e6b57babb2bf19f754081. The consumer has no source/path override. Its expected-failure assertion succeeded; this is a confirmed product failure, not a passing upload qualification.

PHP #63 and Server #143 are now released/closed. Implementation here is next. Preserve the existing worker storage-admission retry behavior when adding upload preparation: upload admission failures must not cause already-computed activity results or command identities to be discarded. No codec change or provider credentials are needed.

[rmcdaniel]

Fixed by #40 and published as Rust SDK 2.0.4 from 96f7515. Release: https://github.com/durable-workflow/sdk-rust/releases/tag/2.0.4 . Publication and registry verification: https://github.com/durable-workflow/sdk-rust/actions/runs/34221603598 . Crate checksum: fa3c917182474b1a3ddda02a4e4fe25169b69c05c3f7b8f8ac3fe7cfceea6363.

A new, separate Cargo consumer installed exactly 2.0.4 from crates.io, with no Git/path SDK override. Cargo metadata confirms registry source and the real Server worker roster reports durable-workflow-rust/2.0.4. On a fresh native Server 2.3.3 / Workflow 2.0.7 / MySQL 8.0.46 database, the installed consumer passed large typed workflow input, activity arguments/result, workflow result, committed condition wait, query/signal resume and an exactly 64 MiB encoded result. Both completed and waiting results plus the maximum result survived cold worker/Server/MySQL restart and fresh client processes. Original run IDs were 01m20d4m0e1w1rz1m5c6zp8k46 and 01m20d4tptfhzj2c715229bs9p.

Server request limit remains 2 MiB, upload limit 64 MiB, PHP heap 128 MiB and HTTP container 256 MiB. No OOM kills; worker SIGKILL was intentional, Server/MySQL stopped cleanly. No Cloud capacity or provider-storage claim follows from this fixture.

All 12 checks on merged source are green. Full tests: 208 unit plus 23 integration/corpus/compile tests. Focused tests cover 13 upload scenarios including roles/namespaces/cache expiry, aggregate limits, integrity failures, full discovery manifests, actual redirect rejection, bounded chunked responses, interruption and single activity execution while uploads are refused. Reproduction is retained in tests/runtime-payloads.md; generated run data is temporary. The previous released-crate HTTP 413 is now resolved without weakening Server admission or Avro semantics.