Explore a Rust interface for CCF applications by achamayou · Pull Request #8200 · microsoft/CCF

Amaury Chamayou (achamayou) · 2026-08-24T13:47:04Z

Summary

This draft explores what it would take to support native CCF applications written in Rust while keeping the integration boundary small and explicit.

It introduces:

a C ABI bridge between the CCF host and Rust application code;
an initial ccf-app Rust crate for endpoint registration, request and response handling, authentication selection, and raw-byte KV access;
CMake support for building and packaging Rust applications alongside native CCF applications;
a basic Rust records application, end-to-end test coverage, and user documentation.

Goal

The goal is to evaluate the viability and ergonomics of Rust as another native CCF application language without exposing C++ implementation details across the boundary. The proposed API deliberately starts small so that ownership, lifetime, panic containment, transaction, concurrency, and packaging concerns can be reviewed before expanding the surface area.

Exploration status

This is exploratory work, not a commitment to a stable or production-supported Rust SDK. The current interface intentionally omits advanced endpoint configuration, custom authentication policies, historical queries, indexing, and commit callbacks. Feedback is especially welcome on the ABI design, safety guarantees, SDK ergonomics, and long-term maintenance implications.

This replays the work from achamayou/CCF#107 onto the current microsoft/CCF main branch so it can be discussed and evaluated in the upstream repository.

Copilot

Pull request overview

Introduces exploratory Rust support for native CCF applications through a C ABI bridge and Rust SDK.

Changes:

Adds endpoint, authentication, response, and raw KV APIs.
Adds Cargo/CMake integration and packaging.
Adds a sample application, E2E coverage, documentation, and changelog entry.

Custom instructions used

.github/copilot-instructions.md
.github/instructions/changelog.instructions.md
.github/instructions/reviewing.instructions.md

Reviewed changes

Copilot reviewed 17 out of 19 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
`CHANGELOG.md`	Announces Rust application support.
`CMakeLists.txt`	Installs Rust sources and registers the E2E test.
`cmake/ccf_app.cmake`	Adds the Rust application build helper.
`cmake/gersemi_definitions.cmake`	Registers the helper for CMake formatting.
`include/ccf/rust_ffi.h`	Defines the public C ABI.
`src/rust/app_bridge.cpp`	Implements the C++ bridge and endpoint registry.
`src/rust/ccf-app/Cargo.toml`	Defines the Rust SDK crate.
`src/rust/ccf-app/Cargo.lock`	Locks the SDK crate.
`src/rust/ccf-app/src/lib.rs`	Implements the Rust-facing API and handlers.
`samples/CMakeLists.txt`	Includes the Rust sample.
`samples/apps/basic_rust/CMakeLists.txt`	Builds the sample application.
`samples/apps/basic_rust/Cargo.toml`	Defines the sample crate.
`samples/apps/basic_rust/Cargo.lock`	Locks sample dependencies.
`samples/apps/basic_rust/rust-toolchain.toml`	Pins Rust 1.90.
`samples/apps/basic_rust/src/lib.rs`	Implements records and health endpoints.
`tests/basic_rust.py`	Exercises authentication and KV behavior.
`doc/build_apps/index.rst`	Adds Rust to the application overview.
`doc/build_apps/get_started.rst`	Links Rust build guidance.
`doc/build_apps/example_rust.rst`	Documents the initial Rust interface.

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Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Preserve compaction retry semantics, reject unsupported HTTP status codes, and keep the CI test bucket inventory in sync. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Stabilize the C ABI, preserve Cargo dependency tracking, register Rust unit tests, enforce unwind panics, and clarify native application trust semantics. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 20 out of 22 changed files in this pull request and generated 5 comments.

Copilot · 2026-08-29T08:53:53Z


 - C++ endpoints can now use `ccf::endpoints::Endpoint::add_openapi_response<Out>()` to document additional HTTP responses in their generated OpenAPI schema without changing the endpoint's primary success response (#8115).
 - New `ledger.max_transaction_size` node configuration option (default `32MB`), which caps the total serialised size of transactions written to the ledger. The limit covers the whole ledger entry: the fixed 8-byte ledger entry header, the ledger encryption header, public domain size field, public domain and encrypted private domain. It is checked before a transaction is applied, so an oversized transaction is now rejected with `413 Payload Too Large` and error code `TransactionTooLarge`, and subsequent transactions are unaffected, where previously an excessively large transaction could terminate the node. Reserved internal signature transactions are exempt because they must fill their reserved ledger version. The limit applies only to newly serialised non-reserved transactions; deserialising existing entries (including during recovery), historical queries and snapshots are unaffected, so entries written under a larger or unset limit remain readable. It must be smaller than `memory.max_msg_size` by at least the ring-buffer range response overhead, which is validated at node startup and by `--check` (#7992).
+- Native CCF applications can now be written in Rust through a minimal API for registering endpoints and accessing raw-byte KV maps (#8200).


Updated the release metadata to add the new unreleased 7.0.14 section above 7.0.13 and synced python/pyproject.toml to 7.0.14 (1019c22).

Copilot · 2026-08-29T09:00:02Z

+            status: if (400..=599).contains(&status) {
+                status
+            } else {
+                500
+            },


Addressed by validating status against the known HTTP error status set in HTTP_STATUS_MAP in EndpointError::new in 941258d.

+Request, response, transaction, and map values borrow the callback context and
+cannot be retained. The SDK requires Rust's ``unwind`` panic strategy so that
+panics are caught at the ABI boundary and become HTTP 500 errors. Builds using
+``panic = "abort"`` are rejected. C++ exceptions are also contained by the
+bridge.


Copilot · 2026-08-29T08:55:57Z

+    let endpoint_error = match result {
+        Ok(Ok(())) => return RawResult::Ok as i32,
+        Ok(Err(error)) => error,
+        Err(_) => EndpointError::internal("Rust endpoint panicked"),


Fixed in 005256d5c by adding a panic-triggering /app/panic sample endpoint and extending tests/basic_rust.py to assert a 500 from the panic path followed by a healthy /app/health response.

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Amaury Chamayou (achamayou) requested a balanced review from Copilot August 26, 2026 12:28

Copilot started reviewing on behalf of Amaury Chamayou (achamayou) August 26, 2026 12:29 View session

Amaury Chamayou (achamayou) force-pushed the achamayou-rust-interface-exploration branch from fc3606c to ae04da5 Compare August 26, 2026 12:31

Copilot AI reviewed Aug 26, 2026

View reviewed changes

Comment thread src/rust/app_bridge.cpp Outdated

Comment thread cmake/ccf_app.cmake Outdated

Comment thread src/rust/ccf-app/src/lib.rs

Comment thread doc/build_apps/example_rust.rst Outdated

Comment thread doc/build_apps/example_rust.rst Outdated

Comment thread include/ccf/rust_ffi.h Outdated

Amaury Chamayou (achamayou) force-pushed the achamayou-rust-interface-exploration branch from b50fb7c to 66b1b47 Compare August 26, 2026 14:42

Copilot AI and others added 11 commits August 28, 2026 15:05

Add Rust application ABI and SDK foundation

da93824

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Add Rust sample tests and documentation

fdd861a

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Finalize Rust SDK packaging and validation fixes

c946e2b

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Address Rust SDK review feedback

7a24948

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Separate Rust app SDK from core Rust archive

c2a4b41

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Address final Rust SDK review feedback

0cd4658

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Use public KV API in Rust bridge

4e6bf97

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Compile Rust bridge with public map type

71d8920

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Reference Rust exploration PR in changelog

99d8628

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Harden Rust bridge integration

8b91d0b

Preserve compaction retry semantics, reject unsupported HTTP status codes, and keep the CI test bucket inventory in sync. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Address Rust interface review feedback

30b12d6

Stabilize the C ABI, preserve Cargo dependency tracking, register Rust unit tests, enforce unwind panics, and clarify native application trust semantics. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Amaury Chamayou (achamayou) force-pushed the achamayou-rust-interface-exploration branch from fa47450 to 30b12d6 Compare August 28, 2026 14:05

Amaury Chamayou (achamayou) requested a review from cjen1-msft August 28, 2026 14:09

Merge branch 'main' into achamayou-rust-interface-exploration

cb80eac

Amaury Chamayou (achamayou) requested a balanced review from Copilot August 28, 2026 17:22

Copilot started reviewing on behalf of Amaury Chamayou (achamayou) August 28, 2026 17:22 View session

Copilot AI reviewed Aug 28, 2026

View reviewed changes

Copilot started work on behalf of Amaury Chamayou (achamayou) August 29, 2026 08:50 View session

Copilot started work on behalf of Amaury Chamayou (achamayou) August 29, 2026 08:51 View session

Copilot AI and others added 3 commits August 29, 2026 08:52

Update 7.0.14 changelog entry and package version

1019c22

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Align EndpointError status validation with HTTP_STATUS_MAP

04c7fd1

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Add Rust panic endpoint for app-boundary test coverage

005256d

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Copilot finished work on behalf of Amaury Chamayou (achamayou) August 29, 2026 08:56

Add comment linking is_known_error_status to HTTP_STATUS_MAP

941258d

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Finalize Rust panic-boundary validation and comment fix

7e966d2

Co-authored-by: achamayou <4016369+achamayou@users.noreply.github.com>

Copilot finished work on behalf of Amaury Chamayou (achamayou) August 29, 2026 09:02

Copilot finished work on behalf of Amaury Chamayou (achamayou) August 29, 2026 09:03

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Explore a Rust interface for CCF applications - #8200

Explore a Rust interface for CCF applications#8200
Amaury Chamayou (achamayou) wants to merge 17 commits into
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Amaury Chamayou (achamayou) commented Aug 24, 2026 •

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Amaury Chamayou (achamayou) commented Aug 24, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Amaury Chamayou (achamayou) commented Aug 24, 2026 •

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