What this PR does / why we need it:

Adds an opt-in GLIDE-backed Redis online read path for Python get_online_features.

The existing redis-py path does command packing, socket parsing, and response handling in Python. Under thread contention, that work repeatedly reacquires the GIL and can make online reads much slower than single-threaded benchmarks suggest.

This PR adds a client: glide option to the Redis online store config. When enabled, Feast uses GLIDE for the batched Redis read while preserving the existing Redis storage layout and default redis-py behavior.

This PR intentionally does not include the HGETALL threshold optimization. That can be evaluated separately.

Scope

• RedisOnlineStoreConfig gains client: redis | glide, defaulting to redis.
• Only the synchronous read paths change (online_read and the batched per-feature-view read behind get_online_features). Writes and get_online_features_async keep using redis-py.
• GLIDE reads the same entity keys (serialize_entity_key + project) and the same hashed field names (_mmh3(f"{fv}:{name}") plus _ts:<fv>) that Feast already writes, so existing data needs no migration.
• connection_string support: host/port, db, password, username, ssl, socket_timeout, socket_connect_timeout. Unknown parameters are logged and ignored. Sentinel is rejected with a clear error because GLIDE has no Sentinel support.
• valkey-glide-sync>=2.5,<3 is a new optional extra, feast[glide]. It is imported lazily so users who never opt in are unaffected. Configuring client: glide without it raises FeastExtrasDependencyImportError naming the extra.

Implementation notes

The read client is selected in one place, RedisOnlineStore._read_hash_fields, which takes a list of (key, fields) HMGET commands and returns one reply per command. Both clients produce the same ordering, so the existing response conversion (_convert_redis_values_to_protobuf) and timestamp handling are untouched.

_glide_hmget_batch builds a single Batch(is_atomic=False) (or ClusterBatch(is_atomic=False) for cluster) and calls exec(batch, raise_on_error=True) once, so the whole fetch is one FFI call.

Three type annotations were corrected because the GLIDE path made the existing inaccuracy visible: _generate_hset_keys_for_features returns hashed bytes keys, not str, and the value sequences accepted by _convert_redis_values_to_protobuf / _get_features_for_entity legitimately contain None for missing fields.

Which issue(s) this PR fixes:

Related to #6856.

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
• Manual tests
• Testing is not required for this change

Commands run:

# Unit tests
uv run python -m pytest sdk/python/tests/unit/infra/online_store/test_redis.py -q
# 35 passed

# Redis-related unit tests together
uv run python -m pytest sdk/python/tests/unit/infra/online_store/test_redis.py \
    sdk/python/tests/unit/infra/online_store/test_redis_versioning.py \
    sdk/python/tests/unit/infra/online_store/test_helpers.py -q
# 65 passed

# Integration tests
uv run python -m pytest --integration \
    sdk/python/tests/integration/online_store/test_redis_glide_client.py -q
# 2 passed

# Lint and format
uv run ruff check <changed files>            # All checks passed!
uv run ruff format --check <changed files>   # 3 files already formatted

# Types
uv run bash -c "cd sdk/python && mypy feast/infra/online_stores/redis.py"
# Success: no issues found in 1 source file

Notes on the test runs

• The integration test seeds rows with the default redis-py client, then reads them back with client: redis and client: glide and asserts the results are byte-identical, both for online_read and for the batched _read_features_per_fv response (including a missing entity). If GLIDE used different keys or field names it would read NOT_FOUND instead of matching.
• I ran the integration test against a live Valkey 9 on localhost:6379 because the Docker daemon on my machine could not create containers (error creating temporary lease: read-only file system). The committed test uses testcontainers with redis:7, matching the existing test_redis_versioning.py, and is skipped when Docker is unavailable.
• glide is added to the ci extra in pyproject.toml, but the pinned lock files (sdk/python/requirements/py*-ci-requirements.txt) need a make lock-python-dependencies-all run before CI installs it. Until then the tests that need the real package skip via importorskip; the mock-based tests, including the missing-dependency error test, still run.
• mypy on feast/infra/online_stores/redis.py is clean. test_redis.py already had 19 mypy errors at master (unrelated pre-existing assertions on Optional dicts and list invariance in online_write_batch test data); this branch reduces that to 16 and adds none. I left those pre-existing errors alone to keep this diff focused.

Misc

The GLIDE batch is non-atomic by design, matching the existing pipeline(transaction=False) behavior. valkey-glide-sync 2.5.0 and 2.5.3 were both checked to confirm the Batch/ClusterBatch/config signatures used here exist across the 2.5 line.

I am happy to add glide to the ci lock files in this PR if you would rather have CI coverage of the GLIDE path immediately.