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Preparation of Model File

This section explains the code for deploying a LangChain-compatible Large Language Model (LLM) API endpoint using the PracticusAI SDK. The model.py handles model initialization, handling payloads, and generating responses. Below is a breakdown of each segment:

Import Statements

import sys 
from datetime import datetime

Global Variables

generator = None
generator: Holds the model instance. Initialized as None and later assigned the LLM object.
sys: Used for interacting with the interpreter, including adding paths for Python to search for modules.
datetime: Facilitates recording timestamps, useful for performance monitoring.

Initialization Function

The init function attempts to import the LLaMA library and build the model with specified parameters.
async def init(model_meta=None, *args, **kwargs):
    global generator
    # Checks if the `generator` is already initialized to avoid redundant model loading.
    if generator is not None:
        print("generator exists, using")
        return

    # If `generator` is not already initialised, builds the generator by loading the desired LLM
    print("generator is none, building")
    model_cache = "/var/practicus/cache" # for details check 02_model_json
    if model_cache not in sys.path:
        sys.path.insert(0, model_cache)

    try:
        from transformers import AutoTokenizer, AutoModelForCausalLM, pipeline
    except Exception as e:
        raise print(f"Failed to import required libraries: {e}")

    # Initialize the local LLM model using transformers:
    def load_local_llm(model_path):
        tokenizer = AutoTokenizer.from_pretrained(model_path)
        model = AutoModelForCausalLM.from_pretrained(model_path)
        model.to('cpu') # Change with cuda or auto to use gpus.
        return pipeline('text-generation', model=model, tokenizer=tokenizer, max_new_tokens=200)

    try:
        generator = load_local_llm(model_cache)
    except Exception as e:
        print(f"Failed to build generator: {e}")
        raise

Cleanup Function

This function is designed to free up resources once they're no longer needed, setting generator back to None and clearing the GPU memory cache to prevent memory leaks, crucial for maintaining performance.
async def cleanup(model_meta=None, *args, **kwargs):
    print("Cleaning up memory")
    global generator
    generator = None
    from torch import cuda
    cuda.empty_cache()

Prediction Wrapper Function

The predict function processes user input and generates responses using the LLM. Key steps include:
async def _predict(payload_dict: dict, **kwargs):

    from practicuscore.gen_ai import PrtLangRequest, PrtLangResponse

    # The payload dictionary is validated against PrtLangRequest.
    practicus_llm_req = PrtLangRequest.model_validate(payload_dict)

    # Converts the validated request object to a dictionary.
    data_js = practicus_llm_req.model_dump_json(indent=2, exclude_unset=True)
    payload = json.loads(data_js)

    # Joins the content field from all messages in the payload to form the prompt string.
    prompt = " ".join([item['content'] for item in payload['messages']])

    # Generate a response from the model
    response = generator(prompt)
    answer = response[0]['generated_text']

    # Creates a PrtLangResponse object with the generated content and metadata about the language model and token usage
    resp = PrtLangResponse(
        content=answer,
        lang_model=payload['lang_model'],
        input_tokens=0,
        output_tokens=0,
        total_tokens=0,
        # additional_kwargs={
        #     "some_additional_info": "test 123",
        # },
    )

    return resp

Summary

This model.py script outlines a robust framework for deploying and interacting with a LLM in a scalable, asynchronous manner. It highlights essential practices like dynamic library loading, concurrent processing with threads, resource management, and detailed logging for performance monitoring. This setup is adaptable to various models and can be tailored to fit specific requirements of different LLM deployments.

Supplementary Files

model.json

{
"download_files_from": "cache/llama-1b-instruct/",
"_comment": "you can also define download_files_to otherwise, /var/practicus/cache is used"
}

model.py

import sys
from transformers import AutoTokenizer, AutoModelForCausalLM, pipeline
from practicuscore.gen_ai import PrtLangMessage, PrtLangRequest, PrtLangResponse
import json

generator = None

async def init(model_meta=None, *args, **kwargs):
    global generator
    if generator is not None:
        print("generator exists, using")
        return

    print("generator is none, building")
    model_cache = "/var/practicus/cache"
    if model_cache not in sys.path:
        sys.path.insert(0, model_cache)

    try:
        from transformers import AutoTokenizer, AutoModelForCausalLM, pipeline
    except Exception as e:
        raise print(f"Failed to import required libraries: {e}")

    # Initialize the local LLM model using transformers:

    def load_local_llm(model_path):
        tokenizer = AutoTokenizer.from_pretrained(model_path)
        model = AutoModelForCausalLM.from_pretrained(model_path)
        model.to('cpu') # Change with cuda or auto to use gpus.
        return pipeline('text-generation', model=model, tokenizer=tokenizer, max_new_tokens=200)

    try:
        generator = load_local_llm(model_cache)
    except Exception as e:
        print(f"Failed to build generator: {e}")
        raise

async def cleanup(model_meta=None, *args, **kwargs):
    print("Cleaning up memory")

    global generator
    generator = None

    from torch import cuda
    cuda.empty_cache()

async def predict(payload_dict: dict, **kwargs):

    from practicuscore.gen_ai import PrtLangRequest, PrtLangResponse

    # The payload dictionary is validated against PrtLangRequest.
    practicus_llm_req = PrtLangRequest.model_validate(payload_dict)

    # Converts the validated request object to a dictionary.
    data_js = practicus_llm_req.model_dump_json(indent=2, exclude_unset=True)
    payload = json.loads(data_js)

    # Joins the content field from all messages in the payload to form the prompt string.
    prompt = " ".join([item['content'] for item in payload['messages']])

    # Generate a response from the model
    response = generator(prompt)
    answer = response[0]['generated_text']

    # Creates a PrtLangResponse object with the generated content and metadata about the language model and token usage
    resp = PrtLangResponse(
        content=answer,
        lang_model=payload['lang_model'],
        input_tokens=0,
        output_tokens=0,
        total_tokens=0,
        # additional_kwargs={
        #     "some_additional_info": "test 123",
        # },
    )

    return resp

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