test_determinism_disagg.py

#!/usr/bin/env python3
# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

"""
Determinism test for KVBM in disaggregated mode.

To make sure KVBM's accuracy, this test suite checks if the model produces
deterministic outputs when same requests are served 1) without KVBM onboarded KV
blocks and 2) with KVBM onboarded KV blocks, when given the same inputs with
fixed seed and temperature=0.

The expected results should be at least 95% match between the two cases.
Compared to aggregated mode, disaggregated mode has some known randomness.
Example reference: https://github.com/vllm-project/vllm/issues/7779#issuecomment-2304967870
"""

import importlib.util
import logging
import os
import signal
import subprocess
import time
from datetime import datetime
from pathlib import Path
from typing import Optional, TextIO

import pytest
import requests

from .common import DeterminismTester, ServerType
from .common import TestDeterminism as BaseTestDeterminism

# Test markers to align with repository conventions
# Todo: enable the rest when kvbm is built in the ci
pytestmark = [
    pytest.mark.kvbm,
    pytest.mark.e2e,
    pytest.mark.slow,
    pytest.mark.gpu_2,
    pytest.mark.nightly,
]


SUCCESS_RATE_THRESHOLD = 0.95


class LLMServerManager:
    """Manages LLM server lifecycle for determinism testing."""

    def __init__(
        self,
        base_url: Optional[str] = None,
        port: Optional[int] = None,
        cpu_cache_blocks: Optional[int] = None,
        gpu_cache_blocks: Optional[int] = None,
        log_dir: Optional[Path] = None,
        server_type: Optional[str] = ServerType.vllm,
    ):
        self.server_type = server_type
        self.port = port or int(os.environ.get("KVBM_SERVER_PORT", "8000"))
        self.base_url = base_url or f"http://localhost:{self.port}"
        self.process_frontend: Optional[subprocess.Popen] = None
        self.process_prefiller: Optional[subprocess.Popen] = None
        self.process_decoder: Optional[subprocess.Popen] = None
        self.cpu_cache_blocks = cpu_cache_blocks
        self.gpu_cache_blocks = gpu_cache_blocks

        # Prepare logging
        self.log_dir = log_dir or Path(".")
        self.log_dir.mkdir(parents=True, exist_ok=True)
        timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
        config_str = (
            f"cpu{cpu_cache_blocks or 'default'}_gpu{gpu_cache_blocks or 'default'}"
        )

        self.prefiller_log_file = (
            self.log_dir / f"{self.server_type}_prefiller_{config_str}_{timestamp}.log"
        )
        self.prefiller_stdout_file: Optional[TextIO] = None
        self.prefiller_stderr_file: Optional[TextIO] = None

        self.decoder_log_file = (
            self.log_dir / f"{self.server_type}_decoder_{timestamp}.log"
        )
        self.decoder_stdout_file: Optional[TextIO] = None
        self.decoder_stderr_file: Optional[TextIO] = None

        # Environment for the process
        self.env = os.environ.copy()
        self.env.update(
            {
                "RUST_BACKTRACE": "1",
                # DynamoConnector connection settings
                "NATS_SERVER": "nats://localhost:4222",
                "ETCD_ENDPOINTS": "http://localhost:2379",
            }
        )

        # CPU cache blocks override via env
        if cpu_cache_blocks is not None:
            self.env["DYN_KVBM_CPU_CACHE_OVERRIDE_NUM_BLOCKS"] = str(cpu_cache_blocks)

        self._set_up_dynamo_config()

        if self.server_type == ServerType.vllm:
            self._set_up_vllm_config(gpu_cache_blocks)
        else:
            raise ValueError(
                f"{self.server_type} is not supported yet in the KVBM test suite"
            )

    def _set_up_dynamo_config(self, router_mode: str = "kv"):
        self.dynamo_frontend_cmd = [
            "python3",
            "-m",
            "dynamo.frontend",
            "--router-mode",
            router_mode,
            "--http-port",
            str(self.port),
        ]

    def _set_up_vllm_config(self, gpu_cache_blocks):
        self.env["VLLM_SERVER_DEV_MODE"] = "1"

        # Construct decoder command
        self.decoder_cmd = [
            "python3",
            "-m",
            "dynamo.vllm",
            "--model",
            os.environ.get("KVBM_MODEL_ID", "deepseek-ai/DeepSeek-R1-Distill-Llama-8B"),
            "--block-size",
            "16",
            "--max-model-len",
            "8000",  # required to fit on L4 GPU when using 8b model
            "--connector",
            "nixl",
        ]

        # Construct prefiller command
        self.prefiller_cmd = [
            "python3",
            "-m",
            "dynamo.vllm",
            "--model",
            os.environ.get("KVBM_MODEL_ID", "deepseek-ai/DeepSeek-R1-Distill-Llama-8B"),
            "--is-prefill-worker",
            "--block-size",
            "16",
            "--max-model-len",
            "8000",  # required to fit on L4 GPU when using 8b model
            "--connector",
            "kvbm",
            "nixl",
        ]

        # GPU blocks override
        if gpu_cache_blocks is not None:
            self.decoder_cmd.extend(
                ["--num-gpu-blocks-override", str(gpu_cache_blocks)]
            )
            self.prefiller_cmd.extend(
                ["--num-gpu-blocks-override", str(gpu_cache_blocks)]
            )

    def start_server(self, timeout: int = 300) -> bool:
        """Start LLM server and wait for readiness."""
        if self.is_server_running():
            self.stop_server()
            time.sleep(5)

        # Open log files
        self.prefiller_stdout_file = open(
            self.prefiller_log_file.with_suffix(".stdout.log"), "w"
        )
        self.prefiller_stderr_file = open(
            self.prefiller_log_file.with_suffix(".stderr.log"), "w"
        )
        if self.prefiller_stdout_file is not None:
            self.prefiller_stdout_file.write(
                f"=== {self.server_type} Prefiller Started at {datetime.now()} ===\nCommand: {' '.join(self.prefiller_cmd)}\n"
            )
            self.prefiller_stdout_file.flush()

        self.decoder_stdout_file = open(
            self.decoder_log_file.with_suffix(".stdout.log"), "w"
        )
        self.decoder_stderr_file = open(
            self.decoder_log_file.with_suffix(".stderr.log"), "w"
        )
        if self.decoder_stdout_file is not None:
            self.decoder_stdout_file.write(
                f"=== {self.server_type} Decoder Started at {datetime.now()} ===\nCommand: {' '.join(self.decoder_cmd)}\n"
            )
            self.decoder_stdout_file.flush()

        # Create separate environment configs for different processes
        decoder_env = self.env.copy()
        decoder_env["CUDA_VISIBLE_DEVICES"] = "0"

        prefiller_env = self.env.copy()
        prefiller_env["CUDA_VISIBLE_DEVICES"] = "1"

        # Launch frontend first
        self.process_frontend = subprocess.Popen(
            self.dynamo_frontend_cmd,
            env=self.env,
            preexec_fn=os.setsid,
        )
        print(f"Frontend process started with PID: {self.process_frontend.pid}")

        # Give frontend time to start up
        time.sleep(5)

        model = os.environ.get(
            "KVBM_MODEL_ID", "deepseek-ai/DeepSeek-R1-Distill-Llama-8B"
        )

        # Try to download the model.
        print("Attempting model download...")
        try:
            subprocess.run(
                f"pip install hf_transfer && HF_HUB_ENABLE_HF_TRANSFER=1 hf download {model}",
                check=True,
                shell=True,
            )
        except subprocess.CalledProcessError:
            print("Model download failed. Is this a locally stored model?")

        # Launch decoder
        self.process_decoder = subprocess.Popen(
            self.decoder_cmd,
            stdout=self.decoder_stdout_file,
            stderr=self.decoder_stderr_file,
            env=decoder_env,
            preexec_fn=os.setsid,
        )
        print(f"Decoder process started with PID: {self.process_decoder.pid}")

        # Launch prefiller
        self.process_prefiller = subprocess.Popen(
            self.prefiller_cmd,
            stdout=self.prefiller_stdout_file,
            stderr=self.prefiller_stderr_file,
            env=prefiller_env,
            preexec_fn=os.setsid,
        )
        print(f"Prefiller process started with PID: {self.process_prefiller.pid}")

        # Give prefiller time to start up
        print(
            "Sleeping for 30 seconds to wait for decoder and prefiller to start up..."
        )
        time.sleep(30)

        # Wait for health
        start_time = time.time()
        while time.time() - start_time < timeout:
            try:
                if self.is_server_running():
                    return True
                if (
                    self.process_frontend.poll() is not None
                    or self.process_prefiller.poll() is not None
                    or self.process_decoder.poll() is not None
                ):
                    self.stop_server()
                    return False
            except Exception as e:
                print(f"Error checking server status: {e}")

            print("Waiting for server to start up:")
            print(f"timeout: {timeout}, elapsed: {int(time.time() - start_time)}")
            time.sleep(5)

        # Timeout
        self.stop_server()
        return False

    def stop_server(self):
        """Stop LLM server and close logs."""
        if self.process_frontend:
            try:
                os.killpg(os.getpgid(self.process_frontend.pid), signal.SIGTERM)
                try:
                    self.process_frontend.wait(timeout=30)
                except subprocess.TimeoutExpired:
                    os.killpg(os.getpgid(self.process_frontend.pid), signal.SIGKILL)
                    self.process_frontend.wait()
            except (ProcessLookupError, OSError):
                pass
            finally:
                self.process_frontend = None
        if self.process_prefiller:
            try:
                os.killpg(os.getpgid(self.process_prefiller.pid), signal.SIGTERM)
                try:
                    self.process_prefiller.wait(timeout=30)
                except subprocess.TimeoutExpired:
                    os.killpg(os.getpgid(self.process_prefiller.pid), signal.SIGKILL)
                    self.process_prefiller.wait()
            except (ProcessLookupError, OSError):
                pass
            finally:
                self.process_prefiller = None
        if self.process_decoder:
            try:
                os.killpg(os.getpgid(self.process_decoder.pid), signal.SIGTERM)
                try:
                    self.process_decoder.wait(timeout=30)
                except subprocess.TimeoutExpired:
                    os.killpg(os.getpgid(self.process_decoder.pid), signal.SIGKILL)
                    self.process_decoder.wait()
            except (ProcessLookupError, OSError):
                pass
            finally:
                self.process_decoder = None
        self._close_log_files()

    def _close_log_files(self):
        if self.prefiller_stdout_file:
            self.prefiller_stdout_file.write(
                f"\n=== Prefiller Stopped at {datetime.now()} ===\n"
            )
            self.prefiller_stdout_file.close()
            self.prefiller_stdout_file = None
        if self.prefiller_stderr_file:
            self.prefiller_stderr_file.close()
            self.prefiller_stderr_file = None

        if self.decoder_stdout_file:
            self.decoder_stdout_file.write(
                f"\n=== Decoder Stopped at {datetime.now()} ===\n"
            )
            self.decoder_stdout_file.close()
            self.decoder_stdout_file = None
        if self.decoder_stderr_file:
            self.decoder_stderr_file.close()
            self.decoder_stderr_file = None

    def is_server_running(self) -> bool:
        try:
            # First check basic health
            response = requests.get(f"{self.base_url}/health", timeout=5)
            if response.status_code != 200:
                return False

            # Then check if the model endpoint is ready with a simple test request
            test_payload = {
                "model": os.environ.get(
                    "KVBM_MODEL_ID", "deepseek-ai/DeepSeek-R1-Distill-Llama-8B"
                ),
                "messages": [{"role": "user", "content": "test"}],
                "max_completion_tokens": 1,
                "temperature": 0,
            }

            response = requests.post(
                f"{self.base_url}/v1/chat/completions",
                headers={"Content-Type": "application/json"},
                json=test_payload,
                timeout=10,
            )
            return response.status_code == 200

        except requests.exceptions.RequestException:
            return False


class DisaggDeterminismTester(DeterminismTester):
    """Disaggregated architecture specific determinism tester."""

    def __init__(
        self,
        base_url: Optional[str] = None,
        model_id: Optional[str] = None,
        server_type: Optional[str] = ServerType.vllm,
    ):
        super().__init__(base_url, model_id, server_type)

    def reset_prefix_cache(self):
        """Reset the prefix cache."""
        print("Resetting prefix cache...")
        # 150 shakespeare requests (each request is 200 words, and roughly 17 blocks) could evict 150 * 17 = 2550 blocks
        shakespeare_count = 150
        for seq_idx in range(1, shakespeare_count + 1):
            start_word = (seq_idx - 1) * self.word_count
            content = self.get_shakespeare_content(start_word)

            if content:
                print(
                    f"Resetting Shakespeare sequence {seq_idx} (words {start_word}-{start_word + self.word_count - 1})..."
                )
                try:
                    self.make_request(content)
                except Exception as e:
                    print(f"Resetting request failed: {e}")
        print("Cache reset done")


@pytest.fixture(scope="function")
def llm_server(request, runtime_services):
    """Start and stop a LLM server for each test with optional cache block overrides.

    To parametrize, use:
      @pytest.mark.parametrize("llm_server", [{"cpu_blocks": 10000, "gpu_blocks": 1000}], indirect=True)
    """
    logger = logging.getLogger("pytest")
    logger.setLevel(logging.INFO)

    cpu_blocks = getattr(request, "param", {}).get("cpu_blocks", None)
    gpu_blocks = getattr(request, "param", {}).get("gpu_blocks", None)
    port = getattr(request, "param", {}).get("port", None)

    # Put logs in the per-test directory set up by tests/conftest.py
    log_dir = Path(request.node.name)

    if importlib.util.find_spec("vllm") is not None:
        server_type = ServerType.vllm
    else:
        pytest.skip("vllm module is not available in the current environment.")

    server_manager = LLMServerManager(
        port=port,
        cpu_cache_blocks=cpu_blocks,
        gpu_cache_blocks=gpu_blocks,
        log_dir=log_dir,
        server_type=server_type,
    )

    start_timeout = int(os.environ.get("KVBM_SERVER_START_TIMEOUT", "600"))
    if not server_manager.start_server(timeout=start_timeout):
        pytest.fail(
            f"Failed to start {server_type} server (cpu_blocks={cpu_blocks}, gpu_blocks={gpu_blocks}, port={server_manager.port})"
        )

    yield server_manager

    server_manager.stop_server()


@pytest.fixture(scope="function")
def tester(llm_server):
    """Create determinism tester bound to the running server's base URL."""
    t = DisaggDeterminismTester(
        base_url=llm_server.base_url, server_type=llm_server.server_type
    )
    t.download_shakespeare_text()
    return t


class TestDeterminismDisagg(BaseTestDeterminism):
    """Test class for determinism validation."""

    @pytest.mark.parametrize(
        "llm_server",
        [
            {
                "cpu_blocks": int(os.environ.get("KVBM_CPU_BLOCKS", "10000")),
                "gpu_blocks": int(os.environ.get("KVBM_GPU_BLOCKS", "1000")),
            },
        ],
        indirect=True,
    )
    def test_determinism_disagg_with_cache_reset(
        self, tester, llm_server, runtime_services
    ):
        """Test determinism across cache reset: run test with warmup, reset cache, run again without warmup."""
        # Call the base class implementation
        super().base_test_determinism_with_cache_reset(
            tester,
            llm_server,
            runtime_services,
            success_rate_threshold=SUCCESS_RATE_THRESHOLD,
        )

    @pytest.mark.parametrize(
        "llm_server",
        [
            {
                "cpu_blocks": int(os.environ.get("KVBM_CPU_BLOCKS", "10000")),
                "gpu_blocks": int(os.environ.get("KVBM_GPU_BLOCKS", "1000")),
            },
        ],
        indirect=True,
    )
    @pytest.mark.kvbm_v2
    def test_determinism_disagg_with_cache_reset_v2(
        self, tester, llm_server, runtime_services, monkeypatch
    ):
        """Test determinism across cache reset: run test with warmup, reset cache, run again without warmup."""
        monkeypatch.setenv("DYN_KVBM_USE_V2_TRANSFER_EXPERIMENTAL", "1")
        # Call the base class implementation
        super().base_test_determinism_with_cache_reset(
            tester,
            llm_server,
            runtime_services,
            success_rate_threshold=SUCCESS_RATE_THRESHOLD,
        )


if __name__ == "__main__":
    # Allow running as script
    pytest.main([__file__, "-v", "-s"])