[GuideLLM Refactor] mock server package creation

src/guidellm/mock_server/__init__.py

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+"""
+GuideLLM Mock Server for OpenAI and vLLM API compatibility.
+"""
+
+from .config import MockServerConfig
+from .server import MockServer
+
+__all__ = ["MockServer", "MockServerConfig"]

src/guidellm/mock_server/config.py

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+"""
+Configuration settings for the mock server component.
+
+Provides centralized configuration management for mock server behavior including
+network binding, model identification, response timing characteristics, and token
+generation parameters. Supports environment variable configuration for deployment
+flexibility with automatic validation through Pydantic settings.
+"""
+
+from __future__ import annotations
+
+from pydantic import Field
+from pydantic_settings import BaseSettings
+
+__all__ = ["MockServerConfig"]
+
+
+class MockServerConfig(BaseSettings):
+    """
+    Configuration settings for mock server behavior and deployment.
+
+    Centralizes all configurable parameters for mock server operation including
+    network settings, model identification, response timing characteristics, and
+    token generation behavior. Environment variables with GUIDELLM_MOCK_SERVER_
+    prefix override default values for deployment flexibility.
+
+    Example:
+    ::
+        config = MockServerConfig(host="0.0.0.0", port=8080, model="custom-model")
+        # Use with environment variables:
+        # GUIDELLM_MOCK_SERVER_HOST=127.0.0.1 GUIDELLM_MOCK_SERVER_PORT=9000
+    """
+
+    host: str = Field(
+        default="127.0.0.1", description="Host address to bind the server to"
+    )
+    port: int = Field(default=8000, description="Port number to bind the server to")
+    workers: int = Field(default=1, description="Number of worker processes to spawn")
+    model: str = Field(
+        default="llama-3.1-8b-instruct",
+        description="Model name to present in API responses",
+    )
+    processor: str | None = Field(
+        default=None,
+        description=(
+            "Processor type to use for token stats, tokenize, and detokenize. "
+            "If None, a mock one is created."
+        ),
+    )
+    request_latency: float = Field(
+        default=3.0,
+        description="Base request latency in seconds for non-streaming responses",
+    )
+    request_latency_std: float = Field(
+        default=0.0,
+        description="Standard deviation for request latency variation",
+    )
+    ttft_ms: float = Field(
+        default=150.0,
+        description="Time to first token in milliseconds for streaming responses",
+    )
+    ttft_ms_std: float = Field(
+        default=0.0,
+        description="Standard deviation for time to first token variation",
+    )
+    itl_ms: float = Field(
+        default=10.0,
+        description="Inter-token latency in milliseconds for streaming responses",
+    )
+    itl_ms_std: float = Field(
+        default=0.0,
+        description="Standard deviation for inter-token latency variation",
+    )
+    output_tokens: int = Field(
+        default=128, description="Number of output tokens to generate in responses"
+    )
+    output_tokens_std: float = Field(
+        default=0.0,
+        description="Standard deviation for output token count variation",
+    )
+
+    class Config:
+        env_prefix = "GUIDELLM_MOCK_SERVER_"
+        case_sensitive = False

src/guidellm/mock_server/handlers/__init__.py

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+"""
+HTTP request handlers for the GuideLLM mock server.
+
+This module exposes request handlers that implement OpenAI-compatible API endpoints
+for the mock server. The handlers provide realistic LLM simulation capabilities
+including chat completions, legacy completions, and tokenization services with
+configurable timing characteristics, token counting, and proper error handling to
+support comprehensive benchmarking and testing scenarios.
+"""
+
+from __future__ import annotations
+
+from .chat_completions import ChatCompletionsHandler
+from .completions import CompletionsHandler
+from .tokenizer import TokenizerHandler
+
+__all__ = ["ChatCompletionsHandler", "CompletionsHandler", "TokenizerHandler"]

src/guidellm/mock_server/handlers/chat_completions.py

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+"""
+OpenAI Chat Completions API endpoint handler for the mock server.
+
+Provides a complete implementation of the /v1/chat/completions endpoint that simulates
+realistic LLM behavior with configurable timing characteristics. Supports both streaming
+and non-streaming responses with proper token counting, latency simulation including
+TTFT (Time To First Token) and ITL (Inter-Token Latency), and OpenAI-compatible error
+handling for comprehensive benchmarking scenarios.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import math
+import time
+import uuid
+
+from pydantic import ValidationError
+from sanic import response
+from sanic.request import Request
+from sanic.response import HTTPResponse, ResponseStream
+from transformers import PreTrainedTokenizer
+
+from guidellm.mock_server.config import MockServerConfig
+from guidellm.mock_server.models import (
+    ChatCompletionChoice,
+    ChatCompletionsRequest,
+    ChatCompletionsResponse,
+    ChatMessage,
+    ErrorDetail,
+    ErrorResponse,
+    Usage,
+)
+from guidellm.mock_server.utils import (
+    MockTokenizer,
+    create_fake_text,
+    create_fake_tokens_str,
+    sample_number,
+    times_generator,
+)
+
+__all__ = ["ChatCompletionsHandler"]
+
+
+class ChatCompletionsHandler:
+    """
+    Handles OpenAI Chat Completions API requests with realistic LLM simulation.
+
+    Implements the /v1/chat/completions endpoint behavior including request validation,
+    response generation, and timing simulation. Supports both streaming and
+    non-streaming modes with configurable latency characteristics for comprehensive
+    benchmarking. Uses either a mock tokenizer or a real tokenizer for accurate token
+    counting and realistic text generation.
+
+    Example:
+    ::
+        config = MockServerConfig(ttft_ms=100, itl_ms=50)
+        handler = ChatCompletionsHandler(config)
+        response = await handler.handle(request)
+    """
+
+    def __init__(self, config: MockServerConfig) -> None:
+        """
+        Initialize the Chat Completions handler with server configuration.
+
+        :param config: Mock server configuration containing timing and behavior settings
+        """
+        self.config = config
+        self.tokenizer = (
+            MockTokenizer()
+            if config.processor is None
+            else PreTrainedTokenizer.from_pretrained(config.processor)
+        )
+
+    async def handle(self, request: Request) -> HTTPResponse:
+        """
+        Process incoming chat completion requests with validation and routing.
+
+        Validates the request payload, handles errors gracefully, and routes to
+        appropriate streaming or non-streaming response handlers based on the
+        request configuration.
+
+        :param request: Sanic HTTP request containing chat completion parameters
+        :return: HTTP response with completion data or error information
+        :raises ValidationError: When request payload fails validation
+        :raises JSONDecodeError: When request contains invalid JSON
+        """
+        try:
+            # Parse and validate request
+            req_data = ChatCompletionsRequest(**request.json)
+        except ValidationError as exc:
+            return response.json(
+                ErrorResponse(
+                    error=ErrorDetail(
+                        message=f"Invalid request: {str(exc)}",
+                        type="invalid_request_error",
+                        code="invalid_request",
+                    )
+                ).model_dump(),
+                status=400,
+            )
+        except (json.JSONDecodeError, TypeError):
+            return response.json(
+                ErrorResponse(
+                    error=ErrorDetail(
+                        message="Invalid JSON in request body",
+                        type="invalid_request_error",
+                        code="invalid_json",
+                    )
+                ).model_dump(),
+                status=400,
+            )
+
+        # Handle streaming vs non-streaming
+        if req_data.stream:
+            return await self._handle_stream(req_data)
+        else:
+            return await self._handle_non_stream(req_data)
+
+    async def _handle_non_stream(self, req: ChatCompletionsRequest) -> HTTPResponse:
+        """
+        Generate complete non-streaming chat completion response.
+
+        Simulates realistic LLM behavior with TTFT and ITL delays, generates
+        appropriate token counts, and returns a complete response with usage
+        statistics and generated content.
+
+        :param req: Validated chat completion request parameters
+        :return: Complete HTTP response with generated completion data
+        """
+        # TTFT delay
+        await asyncio.sleep(
+            sample_number(self.config.ttft_ms, self.config.ttft_ms_std) / 1000.0
+        )
+
+        # Token counts
+        prompt_text = self.tokenizer.apply_chat_template(req.messages)
+        prompt_tokens = len(self.tokenizer(prompt_text))
+        max_tokens = req.max_completion_tokens or req.max_tokens or math.inf
+        completion_tokens_count = min(
+            sample_number(self.config.output_tokens, self.config.output_tokens_std),
+            max_tokens,
+        )
+
+        # ITL delay
+        itl_delay = 0.0
+        delays_iter = iter(times_generator(self.config.itl_ms, self.config.itl_ms_std))
+        for _ in range(int(completion_tokens_count) - 1):
+            itl_delay += next(delays_iter)
+        await asyncio.sleep(itl_delay / 1000.0)
+
+        # Response
+        chat_response = ChatCompletionsResponse(
+            id=f"chatcmpl-{uuid.uuid4().hex[:29]}",
+            model=req.model,
+            choices=[
+                ChatCompletionChoice(
+                    index=0,
+                    message=ChatMessage(
+                        role="assistant",
+                        content=create_fake_text(
+                            int(completion_tokens_count), self.tokenizer
+                        ),
+                    ),
+                    finish_reason="stop",
+                )
+            ],
+            usage=Usage(
+                prompt_tokens=prompt_tokens,
+                completion_tokens=int(completion_tokens_count),
+            ),
+            system_fingerprint=f"fp_{uuid.uuid4().hex[:10]}",
+        )
+
+        return response.json(chat_response.model_dump())
+
+    async def _handle_stream(self, req: ChatCompletionsRequest) -> HTTPResponse:
+        """
+        Generate streaming chat completion response with real-time token delivery.
+
+        Creates a streaming response that delivers tokens incrementally with
+        realistic timing delays. Supports optional usage statistics in the final
+        stream chunk when requested via stream_options.
+
+        :param req: Validated chat completion request with streaming enabled
+        :return: Streaming HTTP response delivering tokens with proper timing
+        """
+
+        async def generate_stream(stream_response):
+            completion_id = f"chatcmpl-{uuid.uuid4().hex[:29]}"
+
+            # TTFT delay
+            await asyncio.sleep(
+                sample_number(self.config.ttft_ms, self.config.ttft_ms_std) / 1000.0
+            )
+
+            # Token counts
+            prompt_text = self.tokenizer.apply_chat_template(req.messages)
+            prompt_tokens = len(self.tokenizer(prompt_text))
+            max_tokens = req.max_completion_tokens or req.max_tokens or math.inf
+            completion_tokens_count = int(
+                min(
+                    sample_number(
+                        self.config.output_tokens, self.config.output_tokens_std
+                    ),
+                    max_tokens,
+                )
+            )
+
+            # Send tokens
+            tokens = create_fake_tokens_str(completion_tokens_count, self.tokenizer)
+            delays_iter = iter(
+                times_generator(self.config.itl_ms, self.config.itl_ms_std)
+            )
+
+            for index, token in enumerate(tokens):
+                if index > 0:
+                    itl_delay = next(delays_iter)
+                    await asyncio.sleep(itl_delay / 1000.0)
+
+                chunk_data = {
+                    "id": completion_id,
+                    "object": "chat.completion.chunk",
+                    "created": int(time.time()),
+                    "model": req.model,
+                    "choices": [
+                        {
+                            "index": 0,
+                            "delta": {"content": token},
+                            "finish_reason": None,
+                        }
+                    ],
+                }
+                await stream_response.write(f"data: {json.dumps(chunk_data)}\n\n")
+
+            # Send final chunk with finish reason
+            final_chunk = {
+                "id": completion_id,
+                "object": "chat.completion.chunk",
+                "created": int(time.time()),
+                "model": req.model,
+                "choices": [
+                    {
+                        "index": 0,
+                        "delta": {},
+                        "finish_reason": "stop",
+                    }
+                ],
+            }
+            await stream_response.write(f"data: {json.dumps(final_chunk)}\n\n")
+
+            # Send usage if requested
+            if req.stream_options and req.stream_options.include_usage:
+                usage_chunk = {
+                    "id": completion_id,
+                    "object": "chat.completion.chunk",
+                    "created": int(time.time()),
+                    "model": req.model,
+                    "choices": [],
+                    "usage": {
+                        "prompt_tokens": prompt_tokens,
+                        "completion_tokens": completion_tokens_count,
+                        "total_tokens": prompt_tokens + completion_tokens_count,
+                    },
+                }
+                await stream_response.write(f"data: {json.dumps(usage_chunk)}\n\n")
+
+            # End stream
+            await stream_response.write("data: [DONE]\n\n")
+
+        return ResponseStream(  # type: ignore[return-value]
+            generate_stream,
+            content_type="text/event-stream",
+            headers={
+                "Cache-Control": "no-cache",
+                "Connection": "keep-alive",
+                "X-Accel-Buffering": "no",
+            },
+        )