Summary

This adds an in-tree Chronon bridge for Feast. Chronon remains the owner of feature computation, materialization, and online serving; Feast provides registry/source/store integration for historical retrieval and online reads.

The integration includes:

• ChrononSource for Chronon materialization metadata, Join/GroupBy routing metadata, and source validation
• ChrononOfflineStore for reading Chronon-produced Parquet materializations with point-in-time historical retrieval
• ChrononOnlineStore for get_online_features reads through Chronon's feature service
• ChrononProvider registration as a passthrough provider alias for Chronon-backed repos
• reference docs for Chronon data sources, offline store, and online store
• unit, stub integration, optional live-service integration, and a Chronon-specific PR workflow
• examples/chronon demo covering offline historical retrieval and online reads against Chronon's quickstart service

Notable details

This keeps the Feast/Chronon boundary intentionally narrow:

• Feast does not launch Chronon jobs, schedule backfills, or manage Chronon materialization.
• Offline retrieval selects the latest Chronon row at or before the entity timestamp, with created_timestamp_column used to choose the latest duplicate event timestamp.
• Online reads support both Chronon Joins and GroupBys, URL-encode Chronon object names, and validate Chronon response shape before converting values.
• The live-service workflow now clones a pinned airbnb/chronon checkout instead of relying on a nonexistent submodule or top-level chronon/ directory.
• The local Chronon launcher discovers the built service jar, writes the Java service PID, and can stop the full local stack cleanly.

Testing

Ran locally:

• Installed sbt, checked out airbnb/chronon at 6c0b8de9f0301521baf61a46ff3083c566fb4052, built the quickstart Mongo implementation jar, and built the Chronon service jar with Java 11 and Thrift 0.13.
• CHRONON_REPO=/Users/farceo/.codex/worktrees/ecbd/chronon JAVA_BIN=/opt/homebrew/opt/openjdk@11/bin/java CHRONON_SERVICE_PORT=19000 infra/scripts/chronon/start-local-chronon-service.sh (CHRONON_SERVICE_URL=http://127.0.0.1:19000; Chronon quickstart fetch returned purchase_price_sum_30d=1253 and refund_amt_sum_30d=1269)
• CHRONON_SERVICE_URL=http://127.0.0.1:19000 uv run python examples/chronon/run_demo.py (offline demo returned completed_rides_7d=[18, 7]; online demo returned 1253 and 1269)
• CHRONON_SERVICE_URL=http://127.0.0.1:19000 uv run pytest -c sdk/python/pytest.ini sdk/python/tests/integration/online_store/test_chronon_online_store_real_service.py --integration -q (1 passed)
• uv run pytest -c sdk/python/pytest.ini sdk/python/tests/unit/infra/online_stores/chronon_online_store sdk/python/tests/unit/infra/offline_stores/contrib/chronon_offline_store sdk/python/tests/integration/online_store/test_chronon_online_store.py sdk/python/tests/integration/offline_store/test_chronon_offline_store.py --integration -q (7 passed)
• uv run ruff format infra/scripts/chronon/chronon_service_launcher.py examples/chronon/run_demo.py
• uv run ruff check infra/scripts/chronon/chronon_service_launcher.py examples/chronon/run_demo.py
• bash -n infra/scripts/chronon/start-local-chronon-service.sh infra/scripts/chronon/stop-local-chronon-service.sh
• uv run python examples/chronon/run_demo.py --offline-only
• uv run pre-commit run detect-secrets --files examples/chronon/README.md infra/scripts/chronon/start-local-chronon-service.sh .github/workflows/pr_chronon_integration_tests.yml
• git diff --check

The live Chronon stack was stopped after verification, and cleanup left no Chronon Java process, listener, or Docker containers running.

Follow-ups

Open questions for follow-up PRs:

• whether to add caching or a prebuilt image for the Chronon live-service CI path
• whether future Chronon support should expose richer metadata/discovery from Chronon configs
• whether to add provider-specific docs/examples beyond the reference pages once the bridge API settles