RESP (Redis/Valkey)
===================

An L2 adapter backed by a native RESP (Redis Serialization Protocol)
connector, targeting **Redis** or **Valkey** servers. I/O is dispatched
through a C++ worker-thread pool.

**Required fields:**

- ``host``: Redis/Valkey server hostname or IP.
- ``port``: Server port (positive integer).

**Optional fields:**

- ``num_workers`` (int, default ``8``): C++ worker threads for I/O (> 0).
- ``username`` (string, default ``""``): Auth username.
- ``password`` (string, default ``""``): Auth password.
- ``max_capacity_gb`` (float, default ``0``): Max L2 capacity in GB for usage
  tracking / aggregate eviction. ``0`` disables tracking.

When ``host``, ``port``, ``username``, or ``password`` are left empty, the
adapter falls back to the corresponding environment variables at creation
time: ``LMCACHE_RESP_HOST``, ``LMCACHE_RESP_PORT``, ``LMCACHE_RESP_USERNAME``,
``LMCACHE_RESP_PASSWORD``.

**Configuration examples:**

.. code-block:: bash

    # Basic Redis/Valkey
    --l2-adapter '{"type": "resp", "host": "127.0.0.1", "port": 6379}'

    # With auth, more workers, and a capacity cap
    --l2-adapter '{"type": "resp", "host": "redis.internal", "port": 6379, "username": "lmcache", "password": "secret", "num_workers": 16, "max_capacity_gb": 50}'