Filecoin Proving Subsystem (FPS)

The Filecoin Proving Subsystem provides the storage proofs required by the Filecoin protocol. It is implemented entirely in Rust, as a series of partially inter-dependent crates – some of which export C bindings to the supported API. This decomposition into distinct crates/modules is relatively recent, and in some cases current code has not been fully refactored to reflect the intended eventual organization.

There are currently four different crates:

• Storage Proofs (storage-proofs) A library for constructing storage proofs – including non-circuit proofs, corresponding SNARK circuits, and a method of combining them.

  storage-proofs is intended to serve as a reference implementation for Proof-of-Replication (PoRep), while also performing the heavy lifting for filecoin-proofs.

  Primary Components:

  • PoR (Proof-of-Retrievability: Merkle inclusion proof)
  • DrgPoRep (Depth Robust Graph Proof-of-Replication)
  • ZigZagDrgPoRep (implemented as a specialized LayeredDrgPoRep)
  • PoSt (Proof-of-Spacetime)

• Filecoin Proofs (filecoin-proofs) A wrapper around storage-proofs, providing an FFI-exported API callable from C (and in practice called by go-filecoin via cgo). Filecoin-specific values of setup parameters are included here, and circuit parameters generated by Filecoin’s (future) trusted setup will also live here.

• Sector Base (sector-base) A sector database abstracting away underlying storage considerations. This abstraction will allow for alternate implementations mapping logical sectors to physical storage – facilitating both support for miner specialization, and configurable adaptation to a given miner’s physical hardware and preferences.

• Storage Backend (storage-backend) The storage-backend crate is intended to contain abstractions and implementations of non-Filecoin-specific storage mechanisms require by storage-proofs. However, for the sake of simplicity, it is currently an empty placeholder.

  

Design Notes

Earlier in the design process, we considered implementing what has become the FPS in Go – as a wrapper around potentially multiple SNARK circuit libraries. We eventually decided to use bellman – a library developed by Zcash, which supports efficient pedersen hashing inside of SNARKs. Having made that decision, it was natural and efficient to implement the entire subsystem in Rust. We considered the benefits (self-contained codebase, ability to rely on static typing across layers) and costs (developer ramp-up, sometimes unwieldiness of borrow-checker) as part of that larger decision and determined that the overall project benefits (in particular ability to build on Zcash’s work) outweighed the costs.

We also considered whether the FPS should be implemented as a standalone binary accessed from go-filecoin either as a single-invocation CLI or as a long-running daemon process. Bundling the FPS as an FFI dependency was chosen for both the simplicity of having a Filecoin node deliverable as a single monolithic binary, and for the (perceived) relative development simplicity of the API implementation.

If at any point it were to become clear that the FFI approach is irredeemably problematic, the option of moving to a standalone FPS remains. However, the majority of technical problems associated with calling from Go into Rust are now solved, even while allowing for a high degree of runtime configurability. Therefore, continuing down the same path we have already invested in, and have begun to reap rewards from, seems likely.

Install and configure Rust

NOTE: If you have installed rust-fil-proofs incidentally, as a submodule of go-filecoin, then you may already have installed Rust.

The instructions below assume you have independently installed rust-fil-proofs in order to test, develop, or experiment with it.

Install Rust.

Configure to use nightly:

> rustup default nightly

Build

> cargo build --release --all

Test

> cargo test --all

Examples

> cargo build --all --examples --release

Running them

> ./target/release/examples/merklepor
> ./target/release/examples/drgporep
> ./target/release/examples/drgporep-vanilla
> ./target/release/examples/drgporep-vanilla-disk

Benchmarks

> cargo bench --all

To benchmark the examples you can bencher.

# build the script
> cargo build
# run the benchmarks
> ./target/debug/bencher

The results are written into the .bencher directory, as JSON files. The benchmarks are controlled through the bench.config.toml file.

Note: On macOS you need gtime (brew install gnu-time), as the built in time command is not enough.

Logging

For better logging with backtraces on errors, developers should use expects rather than expect on Result<T, E> and Option<T>.

Developers can control rust-fil-proofs logging through environment variables:

• FIL_PROOFS_LOG_JSON

  Default: false

  Options: true, false

  This is used to enable or disable logging as JSON. If it is true, log entries will be sent to stdout as JSON. Otherwise, log entries will be sent to stdout as plain text.

• FIL_PROOFS_MIN_LOG_LEVEL

  Default: 4

  Options: 1, 2, 3, 4, 5, 6

  This is used to filter log entries. All log entries at the specified level or below will be sent to stdout.

  Logging Macro	Level Code	Description
  crit!	1	An error that should force shutdown of the application to prevent data loss (or further data loss). Reserved for situations in which there is guaranteed to have been data corruption or loss.
  error!	2	An error occurred, generally something you would consider asserting in a debug build.
  warning!	3	A warning often indicates an unexpected (but not fatal) state.
  info!	4	An informational message, often indicates the current program state.
  debug!	5	A debug message, useful for debugging but too verbose to be turned on normally.
  trace!	6	A message that will be printed a lot, useful for debugging program flow and will probably impact performance.

Memory Leak Detection

To run the leak detector against the FFI-exposed portion of libfilecoin_proofs, simply run the FFI example with leak detection enabled. On a Linux machine, you can run the following command:

RUSTFLAGS="-Z sanitizer=leak" cargo run --release --package filecoin-proofs --example ffi --target x86_64-unknown-linux-gnu

If using mac OS, you'll have to run the leak detection from within a Docker container. After installing Docker, run the following commands to build and run the proper Docker image and then the leak detector itself:

docker build -t foo -f ./Dockerfile-ci . && \
  docker run \
    -it \
    -e RUSTFLAGS="-Z sanitizer=leak" \
    --privileged \
    -w /mnt/crate \
    -v `pwd`:/mnt/crate -v $(TMP=$(mktemp -d) && mv ${TMP} /tmp/ && echo /tmp${TMP}):/mnt/crate/target \
    foo:latest \
    cargo run --release --package filecoin-proofs --example ffi --target x86_64-unknown-linux-gnu

Generate Documentation

First, navigate to the rust-fil-proofs directory.

• If you installed rust-fil-proofs automatically as a submodule of go-filecoin:

> cd <go-filecoin-install-path>/go-filecoin/proofs/rust-fil-proofs

• If you cloned rust-fil-proofs manually, it will be wherever you cloned it:

> cd <install-path>/rust-fil-proofs

[Note that the version of rust-fil-proofs included in go-filecoin as a submodule is not always the current head of rust-fil-proofs/master. For documentation corresponding to the latest source, you should clone rust-fil-proofs yourself.]

Now, generate the documentation:

> cargo doc --all --no-deps

View the docs by pointing your browser at: …/rust-fil-proofs/target/doc/proofs/index.html.

---

API Reference

The FPS is accessed from go-filecoin via FFI calls to its API, which is the union of the APIs of its constituents:

The Rust source code serves as the source of truth defining the FPS APIs. View the source directly:

• filecoin-proofs
• sector-base.

Or better, generate the documentation locally (until repository is public). Follow the instructions to generate documentation above. Then navigate to:

• Sector Base API: …/rust-fil-proofs/target/doc/sector_base/api/index.html

• Filecoin Proofs API: …/rust-fil-proofs/target/doc/filecoin_proofs/api/index.html

• Go implementation of filecoin-proofs sectorbuilder API and associated interface structures.

• Go implementation of filecoin-proofs verifier API and associated interface structures.

Contributing

See Contributing

License

The Filecoin Project is dual-licensed under Apache 2.0 and MIT terms:

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)