feat: Add Chronon online and offline store integrations - #6188

Summary

Add a read integration for Chronon-backed features. Feast registers Chronon source metadata, retrieves historical features from local Parquet materializations, and reads online features through Chronon's Join or GroupBy HTTP service. Chronon continues to own computation, scheduling, materialization, and serving infrastructure.

The integration includes source/store/provider registration, schema-aware online conversion and configurable HTTP retries, point-in-time historical joins with TTL and duplicate timestamp handling, local on-demand transforms, Parquet saved datasets, reference documentation, and a runnable checkout-risk demo.

Updated against master at fac0f88d5. Historical retrieval now supports entityless views and preserves request columns that collide with internal row-ordering names. Regression tests cover both cases.

The Chronon workflow runs unit and stub integration tests separately, uses an ARM64 runner for the quickstart image, installs sbt through its setup action, and builds only the required Thrift compiler. The launcher pins the quickstart and MongoDB images and reports failed container startup immediately. MongoDB 7.0 avoids the observed MongoDB 8+ startup incompatibility on the local Linux 7.0 kernel.

Validation

Local Python 3.11 validation on October 5, 2026:

• 88 focused unit tests passed, including adapters, saved datasets, example, launcher, CPU wheel hashes, and offline-server/FIPS coverage.
• 34 core regression tests passed for FeatureStore, feature views, data sources, and online responses.
• 7 offline/HTTP-stub integration tests passed.
• The real Chronon/MongoDB integration test passed with Chronon at 6c0b8de9f0301521baf61a46ff3083c566fb4052.
• Offline and online demos passed. All 30 checkout feature values for users 5, 7, and 999999 matched direct Chronon responses, allowing Float32 rounding and preserving missing values.
• Changed Python files passed Ruff lint and formatting; all six adapter/provider source files passed mypy. Shell syntax and launcher secret scanning passed.
• The existing 22-slide summit presentation rebuilt without changes; its September recording remains a dated artifact.

CI validation at 1274ce368 on October 5: Chronon unit, HTTP-stub, and real-service integration tests passed; lint passed; Linux Python 3.10, 3.11, and 3.12 unit jobs, Go unit tests, and UI unit tests passed. The workflow now successfully builds Thrift 0.13 from Apache’s GitHub source. macOS and broader integration jobs were still running at this update. Ray and DuckDB integration jobs stop before tests at a pre-existing Pixi lockfile mismatch; pyproject.toml and pixi.lock are unchanged from the base branch.

Scope

Offline joins execute locally in pandas; this does not launch Chronon jobs, provide distributed historical execution, or add Go/Java adapters. The demo and correctness checks are not performance or production-readiness benchmarks.

Related presentation: #6850.