What this PR does / why we need it:

This PR introduces comprehensive feature quality monitoring capabilities to Feast, enabling proactive tracking of feature distributions and data quality metrics. Currently, Feast has no built-in tools for monitoring feature health in production — ML teams must build custom solutions to detect issues like distribution shifts, elevated null rates, or degraded data quality before they silently impact model performance.

What it adds:

Core Monitoring Engine

• Hybrid computation engine — SQL push-down on the native OfflineStore as the primary compute path, with a Python-based (PyArrow/NumPy) fallback for backends that don't implement native compute. This leverages the offline store as a compute engine (same architecture as Feast materialization).
• Fully native storage — Monitoring metrics are stored within the configured OfflineStore backend itself (no separate monitoring database). Six static methods on the OfflineStore base class (compute_monitoring_metrics, get_monitoring_max_timestamp, ensure_monitoring_tables, save_monitoring_metrics, query_monitoring_metrics, clear_monitoring_baseline) handle compute and storage.
• PyArrow-based metrics computation (MetricsCalculator) — Backend-agnostic statistical computation as fallback, supporting:
  • Numeric features: mean, stddev, min/max, percentiles (p50/p75/p90/p95/p99), null rate, histograms
  • Categorical features: top-N value counts with other/unique counts
  • Automatic feature type classification from Feast's PrimitiveFeastType and ValueType

Multi-Backend Support (8 Offline Stores)

All 6 native monitoring methods implemented for each backend with dialect-specific SQL:

Multi-Granularity Time-Series Metrics

• 5 granularities: daily, weekly, biweekly, monthly, quarterly
• Auto-compute mode: Detects latest event timestamp and computes all granularities in one job
• Pre-computed metrics stored per date + granularity for fast retrieval
• On-demand transient compute: Fresh statistics for arbitrary date ranges (not stored)

Batch + Log Data Source Support

• Batch source: Reads from the feature view's batch_source via OfflineStore.pull_all_from_table_or_query()
• Log source: Reads from feature serving logs via FeatureService.logging_config destination, using __log_timestamp as event timestamp
• Feature name normalization: Prefixed log column names (driver_stats__conv_rate) are parsed back to their original feature_view_name + feature_name for storage compatibility and drift detection
• data_source_type column (batch / log) differentiates metrics in storage

Orchestration Service (MonitoringService)

• Ties registry, offline store, calculator, and storage together
• Computes and aggregates metrics at feature, feature view, and feature service levels
• Cached OfflineStore instance for performance
• Unified compute/timestamp methods handling both batch and log paths with SQL push-down + fallback

Shared Utilities (monitoring_utils.py)

• Centralized table name constants, column lists, PK definitions
• monitoring_table_meta(), opt_float(), empty_numeric_metric(), empty_categorical_metric(), normalize_monitoring_row(), build_view_aggregate()
• Used by all 8 backends — eliminates duplication and ensures consistency

DQM Job Engine (DQMJobManager)

• Asynchronous job abstraction for metric computation (compute, baseline, auto_compute)
• Job status tracking in feast_monitoring_jobs table
• Supports future integration with Ray/Spark job runners

REST API (/monitoring/)

All endpoints support cascading filters: project, feature_service_name, feature_view_name, feature_name, granularity, data_source_type, date range.

RBAC enforced using existing AuthzedAction.DESCRIBE (read) and AuthzedAction.UPDATE (compute).

CLI (feast monitor run)

Options:
  --feature-view TEXT     Feature view name (omit for all)
  --feature-name TEXT     Feature name(s), repeatable
  --start-date TEXT       Start date YYYY-MM-DD (omit for auto-detect)
  --end-date TEXT         End date YYYY-MM-DD (omit for auto-detect)
  --granularity TEXT      daily | weekly | biweekly | monthly | quarterly
  --set-baseline          Mark this computation as baseline
  --source-type TEXT      batch | log | all (default: batch)

Auto-Baseline on feast apply

• Automatically queues baseline metric computation for new features on feast apply
• Non-blocking (async DQM job), idempotent (skips existing baselines)
• Configurable — can be disabled via feature_store.yaml:

feature_server:
  dqm:
    distribution:
      initial:
        enabled: false

Feast Operator Support

• New CRD types: DqmConfig, DqmDistributionConfig, DqmInitialDistributionConfig added to FeatureStoreSpec
• Operator generates feature_server.dqm section in feature_store.yaml when DQM config is set
• DeepCopy methods auto-generated via make generate
• Disabling auto-baseline from operator CR:

apiVersion: feast.dev/v1
kind: FeatureStore
spec:
  feastProject: my_project
  dqm:
    distribution:
      initial:
        enabled: false

Documentation

• How-to guide: docs/how-to-guides/feature-monitoring.md — Production setup, CLI usage, REST API reference, orchestrator integration (Airflow, KFP, cron, K8s CronJob), backend compatibility table
• Quickstart notebook: examples/monitoring/monitoring-quickstart.ipynb — 12-step hands-on walkthrough with visualization examples
• docs/SUMMARY.md updated with links to both

Design decisions:

• Native OfflineStore compute + storage — Each backend implements its own SQL push-down for metrics calculation and uses its native UPSERT/MERGE for storage. No separate monitoring database needed.
• Hybrid fallback — Backends that don't implement native compute fall back to Python/PyArrow, ensuring all offline stores are supported.
• Separate /monitoring/ route rather than extending existing /metrics/ — The existing metrics route serves registry inventory metadata; monitoring serves statistical feature quality data with a different data path.
• DQM Job Engine for async computation — Supports future Ray/Spark integration for distributed metric computation.

Which issue(s) this PR fixes:

Partially Fixes #5919

Checks

• I've made sure the tests are passing.
• My commits are signed off (git commit -s)
• My PR title follows conventional commits format

Testing Strategy

• Unit tests
• Integration tests
• Operator unit tests (Ginkgo)

Test coverage (all passing):

Snyk SAST scan: 0 vulnerabilities across all new files.