test(MLP-6153): add unit tests for /model/info cache-miss reload on Terraform race condition

Cover the fix that triggers proxy_config.add_deployment() when llm_router
returns None for a specific model ID, preventing the Terraform provider from
seeing "Root object was present, but now absent" due to multi-replica cache lag.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

tests/proxy_unit_tests/test_model_info_cache_reload.py

@@ -0,0 +1,171 @@
+"""
+Tests for the /model/info cache-miss reload fix (MLP-6153).
+
+When llm_router.get_deployment() returns None for a given model ID, the handler
+must call proxy_config.add_deployment() to reload the router cache from the DB,
+then retry the lookup before raising a 400. This covers the multi-replica
+eventual-consistency race where the pod serving the Read-after-Apply hasn't yet
+loaded the newly created model into its local router cache.
+"""
+import pytest
+import litellm.proxy.proxy_server as proxy_server
+from unittest.mock import AsyncMock, MagicMock
+from fastapi import HTTPException
+from litellm.proxy._types import UserAPIKeyAuth
+from litellm.proxy.proxy_server import model_info_v1
+
+
+def _make_deployment(model_id: str = "test-model-id") -> MagicMock:
+    """Return a minimal mock Deployment accepted by _get_proxy_model_info."""
+    deployment = MagicMock()
+    deployment.model_dump.return_value = {
+        "model_name": "claude-sonnet-4-5",
+        "litellm_params": {"model": "vertex_ai/claude-sonnet-4-5", "custom_llm_provider": "vertex_ai"},
+        "model_info": {"id": model_id, "base_model": "claude-sonnet-4-5"},
+    }
+    return deployment
+
+
+def _mock_proxy_config(add_deployment_side_effect=None) -> MagicMock:
+    cfg = MagicMock()
+    cfg.add_deployment = AsyncMock(side_effect=add_deployment_side_effect)
+    return cfg
+
+
+@pytest.mark.asyncio
+async def test_model_info_returns_deployment_when_cache_is_warm():
+    """Happy path: router cache already has the model, no reload needed."""
+    deployment = _make_deployment()
+    mock_router = MagicMock()
+    mock_router.get_deployment.return_value = deployment
+
+    mock_proxy_cfg = _mock_proxy_config()
+
+    setattr(proxy_server, "llm_router", mock_router)
+    setattr(proxy_server, "llm_model_list", [{"model_name": "claude-sonnet-4-5"}])
+    setattr(proxy_server, "prisma_client", MagicMock())
+    setattr(proxy_server, "proxy_config", mock_proxy_cfg)
+    setattr(proxy_server, "proxy_logging_obj", MagicMock())
+
+    resp = await model_info_v1(
+        user_api_key_dict=UserAPIKeyAuth(models=[]),
+        litellm_model_id="test-model-id",
+    )
+
+    assert resp["data"][0]["model_name"] == "claude-sonnet-4-5"
+    mock_proxy_cfg.add_deployment.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_model_info_reloads_cache_on_miss_and_returns_deployment():
+    """
+    Core regression test: router returns None on first call (cache miss),
+    add_deployment() is triggered, second call succeeds.
+    This is the exact race condition that caused the Terraform provider error.
+    """
+    deployment = _make_deployment()
+    mock_router = MagicMock()
+    mock_router.get_deployment.side_effect = [None, deployment]
+
+    mock_proxy_cfg = _mock_proxy_config()
+
+    setattr(proxy_server, "llm_router", mock_router)
+    setattr(proxy_server, "llm_model_list", [{"model_name": "claude-sonnet-4-5"}])
+    setattr(proxy_server, "prisma_client", MagicMock())
+    setattr(proxy_server, "proxy_config", mock_proxy_cfg)
+    setattr(proxy_server, "proxy_logging_obj", MagicMock())
+
+    resp = await model_info_v1(
+        user_api_key_dict=UserAPIKeyAuth(models=[]),
+        litellm_model_id="test-model-id",
+    )
+
+    assert resp["data"][0]["model_name"] == "claude-sonnet-4-5"
+    mock_proxy_cfg.add_deployment.assert_called_once()
+    assert mock_router.get_deployment.call_count == 2
+
+
+@pytest.mark.asyncio
+async def test_model_info_raises_400_when_model_absent_after_reload():
+    """
+    If the model is still absent after the cache reload, the endpoint must
+    raise 400 — not silently return empty data (which would confuse Terraform).
+    """
+    mock_router = MagicMock()
+    mock_router.get_deployment.return_value = None  # absent before and after reload
+
+    mock_proxy_cfg = _mock_proxy_config()
+
+    setattr(proxy_server, "llm_router", mock_router)
+    setattr(proxy_server, "llm_model_list", [{"model_name": "claude-sonnet-4-5"}])
+    setattr(proxy_server, "prisma_client", MagicMock())
+    setattr(proxy_server, "proxy_config", mock_proxy_cfg)
+    setattr(proxy_server, "proxy_logging_obj", MagicMock())
+
+    with pytest.raises(HTTPException) as exc_info:
+        await model_info_v1(
+            user_api_key_dict=UserAPIKeyAuth(models=[]),
+            litellm_model_id="unknown-id",
+        )
+
+    assert exc_info.value.status_code == 400
+    assert "not found" in exc_info.value.detail["error"]
+    # Reload was still attempted
+    mock_proxy_cfg.add_deployment.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_model_info_skips_reload_when_no_prisma_client():
+    """
+    If prisma_client is None (no DB configured), there is nothing to reload
+    from. The endpoint should skip the reload and raise 400 directly.
+    """
+    mock_router = MagicMock()
+    mock_router.get_deployment.return_value = None
+
+    mock_proxy_cfg = _mock_proxy_config()
+
+    setattr(proxy_server, "llm_router", mock_router)
+    setattr(proxy_server, "llm_model_list", [{"model_name": "claude-sonnet-4-5"}])
+    setattr(proxy_server, "prisma_client", None)
+    setattr(proxy_server, "proxy_config", mock_proxy_cfg)
+    setattr(proxy_server, "proxy_logging_obj", MagicMock())
+
+    with pytest.raises(HTTPException) as exc_info:
+        await model_info_v1(
+            user_api_key_dict=UserAPIKeyAuth(models=[]),
+            litellm_model_id="test-model-id",
+        )
+
+    assert exc_info.value.status_code == 400
+    mock_proxy_cfg.add_deployment.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_model_info_returns_deployment_even_if_reload_raises():
+    """
+    If add_deployment() itself throws (e.g. DB is temporarily unavailable),
+    the exception must be swallowed and the endpoint falls through to the
+    404 path gracefully — it should not propagate a 500.
+    """
+    mock_router = MagicMock()
+    mock_router.get_deployment.return_value = None
+
+    mock_proxy_cfg = _mock_proxy_config(
+        add_deployment_side_effect=Exception("DB connection lost")
+    )
+
+    setattr(proxy_server, "llm_router", mock_router)
+    setattr(proxy_server, "llm_model_list", [{"model_name": "claude-sonnet-4-5"}])
+    setattr(proxy_server, "prisma_client", MagicMock())
+    setattr(proxy_server, "proxy_config", mock_proxy_cfg)
+    setattr(proxy_server, "proxy_logging_obj", MagicMock())
+
+    with pytest.raises(HTTPException) as exc_info:
+        await model_info_v1(
+            user_api_key_dict=UserAPIKeyAuth(models=[]),
+            litellm_model_id="test-model-id",
+        )
+
+    # Must be 400 (model not found), not 500 (unhandled DB error)
+    assert exc_info.value.status_code == 400