Feast Feature Server (Rust)

Unofficial Rust implementation of the Feast feature server with focus on performance.

Currently supported features

• Online feature retrieval via HTTP REST API.
• Online feature retrieval via gRPC API
• TLS support for both HTTP and gRPC servers.
• Metrics endpoint for Prometheus scraping.
• Health check endpoint.

Supported feature stores:

• File stores: local filesystem, GCS, S3.

Supported online stores:

• Sqlite.
• Redis
  • Available Redis modes: single node, cluster, and sentinel.
  • TLS connections are supported.
  • For available config options, see the CommonConnectionOptions struct in the source code.

Implementation details

Internally, interned strings are used for better performance. Theoretically, this could lead to an out-of-memory error, but this should not be a problem in standard use cases.

Test server

Easiest way to test the server is to use the pull docker image from docker hub.

docker pull pbezglasny/feast-server-rust:latest

Or build the docker image locally

docker build -t feast-feature-server-rust:latest .

Workspace Layout

• feast-server-core: core feature-store domain logic (registry access, online store abstraction, protobuf helpers).
• rest-server: Axum-based HTTP server that exposes online feature retrieval endpoints.
• grpc-server: tonic-based gRPC server scaffolding.
• cli: command-line entrypoint that wires configuration, logging, and server startup.

Prerequisites

• Rust toolchain (stable) with cargo and rustfmt. You can install it using rustup.

Run the HTTP Server

1. Point the CLI at a feature repository. Either change into the repo directory or pass it explicitly:

   FEATURE_REPO_DIR_ENV_VAR=<path-to-your-feature-repo> \
   cargo run -p cli -- serve -h 0.0.0.0 -p 6566

   You can also use --chdir <path> or --feature-store-yaml <file> to override the repository root and feature_store.yaml filename. These options can also be set via the FEATURE_REPO_DIR_ENV_VAR and FEAST_FS_YAML_FILE_PATH environment variables, respectively.
2. Optional flags:
   • --metrics enables a /metrics endpoint backed by axum-prometheus.
   • --key and --cert must be provided together to serve over TLS.
   • --type grpc is accepted by the CLI, but the gRPC server is not implemented yet.

When the server starts it exposes:

• POST /get-online-features expecting a Feast GetOnlineFeaturesRequest payload and returning the online feature vector.
• GET /health for readiness checks (HTTP 200 on success).
• GET /metrics when metrics are enabled.

Development Workflow

• Format: cargo fmt --all
• Lint: cargo clippy --all-targets --all-features -- -D warnings
• Test: cargo test --all