feat(framework:cc): Update C++ SDK for Flower 1.27.0 inflatable objects protocol#6913
feat(framework:cc): Update C++ SDK for Flower 1.27.0 inflatable objects protocol#6913uncleDecart wants to merge 2 commits intoflwrlabs:mainfrom
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…ts protocol The C++ SDK was stuck on the pre-1.13 protocol and could not communicate with modern Flower SuperLinks. This updates it to support the 1.27.0 "inflatable objects" protocol where message payloads are stored in an ObjectStore and transferred via PullObject/PushObject RPCs. Key changes: - Regenerate proto stubs from current .proto definitions (adds message, recorddict, heartbeat, run, fab protos; removes stale recordset/task) - Implement inflate/deflate in serde.cc for bottom-up object reconstruction and top-down serialization with SHA-256 object IDs - Rewrite communicator.cc to use PullMessages/PushMessages/PullObject/ PushObject/ConfirmMessageReceived Fleet API RPCs - Rewrite grpc_rere.cc with ECDSA node authentication and new RPC stubs - Update typing.h with Message/RecordDict/Array types matching Python SDK - Add Docker quickstart (Dockerfile, docker-compose.yml, pyproject.toml) for easy testing with SuperLink + 2 C++ clients + Python ServerApp - Update README with Docker instructions
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Pull request overview
This PR updates the Flower C++ SDK and quickstart example to interoperate with modern Flower SuperLinks (Flower 1.27.0), including the “inflatable objects” protocol and the Fleet API RPC set.
Changes:
- Regenerates/updates C++ protobuf and gRPC stubs for newer protocol definitions (message/recorddict/heartbeat/run/fab, updated node/transport).
- Reworks the C++ client runtime to use Fleet API node lifecycle, message pull/push, object pull/push, and message receipt confirmation.
- Updates the C++ quickstart example with Docker Compose-based end-to-end setup and a minimal Python app scaffold.
Reviewed changes
Copilot reviewed 40 out of 50 changed files in this pull request and generated 11 comments.
Show a summary per file
| File | Description |
|---|---|
| framework/cc/flwr/src/start.cc | Client startup flow updated (register/activate/heartbeat thread/message loop/cleanup). |
| framework/cc/flwr/src/message_handler.cc | Switch from TaskIns/TaskRes handling to Message/RecordDict-based handling. |
| framework/cc/flwr/src/grpc_rere.cc | Implements Fleet RPCs and node auth metadata signing. |
| framework/cc/flwr/src/communicator.cc | Implements PullMessages/PushMessages and inflatable object pull/push/inflate/deflate flow. |
| framework/cc/flwr/include/typing.h | Updates SDK typing to RecordDict/Message/Metadata and new record value variants. |
| framework/cc/flwr/include/start.h | Removes legacy transport gRPC include and aligns includes with new flow. |
| framework/cc/flwr/include/serde.h | Adds RecordDict/Message serde APIs + inflatable object helpers. |
| framework/cc/flwr/include/message_handler.h | Updates handler API to handle_message(Message). |
| framework/cc/flwr/include/grpc_rere.h | Updates communicator interface to Fleet RPCs + node auth support. |
| framework/cc/flwr/include/flwr/proto/transport.pb.h | Regenerated transport proto (adds Scalar uint64 oneof arm). |
| framework/cc/flwr/include/flwr/proto/transport.pb.cc | Regenerated transport proto implementation for Scalar changes. |
| framework/cc/flwr/include/flwr/proto/run.grpc.pb.h | Adds run gRPC stub header (regenerated). |
| framework/cc/flwr/include/flwr/proto/run.grpc.pb.cc | Adds run gRPC stub implementation (regenerated). |
| framework/cc/flwr/include/flwr/proto/recorddict.grpc.pb.h | Adds recorddict gRPC stub header (regenerated). |
| framework/cc/flwr/include/flwr/proto/recorddict.grpc.pb.cc | Adds recorddict gRPC stub implementation (regenerated). |
| framework/cc/flwr/include/flwr/proto/node.pb.h | Regenerated node proto (uint64 node_id, adds NodeInfo). |
| framework/cc/flwr/include/flwr/proto/node.pb.cc | Regenerated node proto implementation (adds NodeInfo). |
| framework/cc/flwr/include/flwr/proto/message.grpc.pb.h | Adds message gRPC stub header (regenerated). |
| framework/cc/flwr/include/flwr/proto/message.grpc.pb.cc | Adds message gRPC stub implementation (regenerated). |
| framework/cc/flwr/include/flwr/proto/heartbeat.pb.h | Adds heartbeat proto header (regenerated). |
| framework/cc/flwr/include/flwr/proto/heartbeat.pb.cc | Adds heartbeat proto implementation (regenerated). |
| framework/cc/flwr/include/flwr/proto/heartbeat.grpc.pb.h | Adds heartbeat gRPC stub header (regenerated). |
| framework/cc/flwr/include/flwr/proto/heartbeat.grpc.pb.cc | Fixes heartbeat gRPC stub source/header includes (regenerated). |
| framework/cc/flwr/include/flwr/proto/fab.pb.cc | Adds fab proto implementation (regenerated). |
| framework/cc/flwr/include/flwr/proto/fab.grpc.pb.h | Adds fab gRPC stub header (regenerated). |
| framework/cc/flwr/include/flwr/proto/fab.grpc.pb.cc | Adds fab gRPC stub implementation (regenerated). |
| framework/cc/flwr/include/communicator.h | Updates Communicator interface to Fleet API and Message-based exchange. |
| framework/cc/flwr/CMakeLists.txt | Adds new protos to generation and links ssl/crypto for node auth. |
| examples/quickstart-cpp/src/main.cc | Updates CLI help text and binary name. |
| examples/quickstart-cpp/README.md | Updates instructions (Docker Compose + local run) and binary naming. |
| examples/quickstart-cpp/pyproject.toml | Adds Python project metadata and flwr run app configuration. |
| examples/quickstart-cpp/Dockerfile | Adds Docker image to build C++ client + Python deps for quickstart. |
| examples/quickstart-cpp/docker-compose.yml | Adds Compose setup for SuperLink + two C++ clients + runner. |
| examples/quickstart-cpp/CMakeLists.txt | Updates build to link ssl/crypto and renames executable. |
| examples/quickstart-cpp/client.py | Adds placeholder Python ClientApp to satisfy app config. |
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- Don't confirm message receipt when objects fail to pull or inflate, preventing permanent message loss on incomplete object transfers - Fix stype parsing in serde.cc that extracted the next JSON key name instead of the actual stype value - Replace uninstantiable NumPyClient placeholder with error-raising client_fn in quickstart-cpp example - Add return value checks for all OpenSSL crypto APIs and validate EC private key scalar is in range [1, order-1] - Return error reply when train/evaluate messages have no content instead of silently sending empty responses - Use sleep_duration from handle_message for reconnect backoff
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| reply.metadata.reply_to_message_id = message.metadata.message_id; | ||
| reply.metadata.group_id = message.metadata.group_id; | ||
| reply.metadata.message_type = msg_type; | ||
| reply.metadata.ttl = 3600.0; |
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Setting every reply to a fixed ttl=3600 can make otherwise valid replies get dropped by SuperLink whenever the incoming message has a shorter remaining lifetime (or is already close to expiry). The reply validator in framework/py/flwr/server/superlink/linkstate/in_memory_linkstate.py rejects replies whose TTL exceeds the maximum allowed window, so this can cause PushMessages to store no result and leave rounds waiting indefinitely. The TTL should be derived from the incoming message (created_at + ttl - now) rather than hardcoded.
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| if (msg_type == "reconnect") { | ||
| keep_going = false; |
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The reconnect branch only flips keep_going and never populates reply content/error or sleep duration, so the client immediately exits without sending the expected disconnect acknowledgement payload (and without honoring server-requested reconnect delay). This produces an invalid/empty reconnect reply path and breaks reconnect semantics compared to the protocol’s control-message flow, which can leave the server side without a usable response for that instruction.
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Description
The C++ SDK was stuck on the pre-1.13 protocol and could not communicate with modern Flower SuperLinks. This updates it to support the 1.27.0 "inflatable objects" protocol where message payloads are stored in an ObjectStore and transferred via PullObject/PushObject RPCs.
Key changes:
Running example seems to work,
cd examples/quickstart-cpp docker compose up --buildNotes
Related issues/PRs
Checklist
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