app.py

import os
import threading
import streamlit as st
from itertools import tee
from chain import ChainBuilder

DATABRICKS_HOST = os.environ.get("DATABRICKS_HOST")
DATABRICKS_TOKEN = os.environ.get("DATABRICKS_TOKEN")
# remove these secrets from the container
# VS_ENDPOINT_NAME = os.environ.get("VS_ENDPOINT_NAME")
# VS_INDEX_NAME = os.environ.get("VS_INDEX_NAME")

if DATABRICKS_HOST is None:
    raise ValueError("DATABRICKS_HOST environment variable must be set")
if DATABRICKS_TOKEN is None:
    raise ValueError("DATABRICKS_TOKEN environment variable must be set")

MODEL_AVATAR_URL= "./VU.jpeg"
MAX_CHAT_TURNS = 10 # limit this for preliminary testing
MSG_MAX_TURNS_EXCEEDED = f"Sorry! The Vanderbilt AI assistant playground is limited to {MAX_CHAT_TURNS} turns in a single history. Click the 'Clear Chat' button or refresh the page to start a new conversation."
# MSG_CLIPPED_AT_MAX_OUT_TOKENS = "Reached maximum output tokens for DBRX Playground"

EXAMPLE_PROMPTS = [
    "How is a data lake used at Vanderbilt University Medical Center?",
    "In a table, what are some of the greatest hurdles to healthcare in the United States?",
    "What does EDW stand for in the context of Vanderbilt University Medical Center?",
    "Code a sql statement that can query a database named 'VUMC'.",
    "Write a short story about a country concert in Nashville, Tennessee.",
    "Tell me about maximum out-of-pocket costs in healthcare.",
]

TITLE = "Vanderbilt AI Assistant"
DESCRIPTION= """Welcome to the first generation Vanderbilt AI assistant! \n 
**Overview and Usage**: This AI assistant is built atop the Databricks DBRX large language model 
and is augmented with additional organization-specific knowledge. Particularly, it has been preliminarily augmented with knowledge of Vanderbilt University Medical Center
terms like **EDW**, **HCERA**, **NRHA** and **thousands more**. (Ask the assistant if you don't know what any of these terms mean!) On the left is a sidebar of **Examples**; 
click any of these examples to issue the corresponding query to the AI.

**Feedback**: Feedback is welcomed, encouraged, and invaluable! To give feedback in regards to one of the model's responses, click the **Give Feedback on Last Response** button just below
the user input bar. This allows you to provide either positive or negative feedback in regards to the model's most recent response. A **Feedback Form** will appear above the model's title. 
Please be sure to select either 👍 or 👎 before adding additional notes about your choice. Be as brief or as detailed as you like! Note that you are making a difference; this 
feedback allows us to later improve this model for your usage through a training technique known as reinforced learning through human feedback. \n

**Disclaimer**: The model has **no access to PHI**. \n

Please provide any additional, larger feedback, ideas, or issues to the email: **[email protected]**. Happy chatting!"""

GENERAL_ERROR_MSG = "An error occurred. Please refresh the page to start a new conversation."

# # To prevent streaming too fast, chunk the output into TOKEN_CHUNK_SIZE chunks
TOKEN_CHUNK_SIZE = 1 # test this number
# if TOKEN_CHUNK_SIZE_ENV is not None:
#     TOKEN_CHUNK_SIZE = int(TOKEN_CHUNK_SIZE_ENV)

QUEUE_SIZE = 20 # maximize this value for adding enough places in the global queue?
# if QUEUE_SIZE_ENV is not None:
#     QUEUE_SIZE = int(QUEUE_SIZE_ENV)

# @st.cache_resource
# def get_global_semaphore():
#     return threading.BoundedSemaphore(QUEUE_SIZE)
# global_semaphore = get_global_semaphore()

st.set_page_config(layout="wide")

st.title(TITLE)
# st.image("sunrise.jpg", caption="Sunrise by the mountains") # TODO add a Vanderbilt related picture to the head of our Space!
st.markdown(DESCRIPTION)
st.markdown("\n")

# use this to format later
with open("./style.css") as css:
    st.markdown( f'<style>{css.read()}</style>' , unsafe_allow_html= True)

if "messages" not in st.session_state:
    st.session_state["messages"] = []

if "feedback" not in st.session_state:
    st.session_state["feedback"] = [None]

def clear_chat_history():
    st.session_state["messages"] = []

st.button('Clear Chat', on_click=clear_chat_history)

# build our chain outside the working body so that its only instantiated once - simply pass it the chat history for chat completion
chain = ChainBuilder().build_chain()

def last_role_is_user():
    return len(st.session_state["messages"]) > 0 and st.session_state["messages"][-1]["role"] == "user"

def text_stream(stream):
    for chunk in stream:
        if chunk["content"] is not None:
            yield chunk["content"]

def get_stream_warning_error(stream):
    error = None
    warning = None
    for chunk in stream:
        if chunk["error"] is not None:
            error = chunk["error"]
        if chunk["warning"] is not None:
            warning = chunk["warning"]
    return warning, error

# @retry(wait=wait_random_exponential(min=0.5, max=2), stop=stop_after_attempt(3))
def chain_call(history):    
    input = {'messages': [{"role": m["role"], "content": m["content"]} for m in history]}
    chat_completion = chain.stream(input)
    return chat_completion

def write_response():
    stream = chat_completion(st.session_state["messages"])
    content_stream, error_stream = tee(stream)
    response = st.write_stream(text_stream(content_stream))
    stream_warning, stream_error = get_stream_warning_error(error_stream)
    if stream_warning is not None:
        st.warning(stream_warning,icon="⚠️")
    if stream_error is not None:
        st.error(stream_error,icon="🚨")
    # if there was an error, a list will be returned instead of a string: https://docs.streamlit.io/library/api-reference/write-magic/st.write_stream
    if isinstance(response, list):
        response = None 
    return response, stream_warning, stream_error

def chat_completion(messages):
    if (len(messages)-1)//2 >= MAX_CHAT_TURNS:
        yield {"content": None, "error": MSG_MAX_TURNS_EXCEEDED, "warning": None}
        return

    chat_completion = None
    error = None
    # *** TODO add code for implementing a global queue with a bounded semaphore?  
    # wait to be in queue
    # with global_semaphore:
    #     try: 
    #         chat_completion = chat_api_call(history_dbrx_format)
    #     except Exception as e:
    #         error = e    
    # chat_completion = chain_call(history_dbrx_format)
    chat_completion = chain_call(messages)
    if error is not None:
        yield {"content": None, "error": GENERAL_ERROR_MSG, "warning": None}
        print(error)
        return
    
    max_token_warning = None
    partial_message = ""
    chunk_counter = 0
    for chunk in chat_completion:
        if chunk is not None:
            chunk_counter += 1
            partial_message += chunk
            if chunk_counter % TOKEN_CHUNK_SIZE == 0:
                chunk_counter = 0
                yield {"content": partial_message, "error": None, "warning": None}
                partial_message = ""
        # if chunk.choices[0].finish_reason == "length":
        #     max_token_warning = MSG_CLIPPED_AT_MAX_OUT_TOKENS

    yield {"content": partial_message, "error": None, "warning": max_token_warning}

# if assistant is the last message, we need to prompt the user
# if user is the last message, we need to retry the assistant.
def handle_user_input(user_input):
    with history:
        response, stream_warning, stream_error = [None, None, None]
        if last_role_is_user():
            # retry the assistant if the user tries to send a new message
            with st.chat_message("assistant", avatar=MODEL_AVATAR_URL):
                response, stream_warning, stream_error = write_response()
        else:
            st.session_state["messages"].append({"role": "user", "content": user_input, "warning": None, "error": None})
            with st.chat_message("user", avatar="🧑‍💻"):
                st.markdown(user_input)
            stream = chat_completion(st.session_state["messages"])
            with st.chat_message("assistant", avatar=MODEL_AVATAR_URL):
                response, stream_warning, stream_error = write_response()
        
        st.session_state["messages"].append({"role": "assistant", "content": response, "warning": stream_warning, "error": stream_error})

def feedback():
    with st.form("feedback_form"):
        st.title("Feedback Form")
        st.markdown("Please select either 👍 or 👎 before providing a reason for your review of the most recent response. Dont forget to click submit!")
        rating = st.feedback()
        feedback = st.text_input("Please detail your feedback: ")
        # implement a method for writing these responses to storage!
        submitted = st.form_submit_button("Submit Feedback")

main = st.container()
with main:
    if st.session_state["feedback"][-1] is not None: # TODO clean this up in a fn?
            st.markdown("Thank you! Feedback received! Type a new message to continue your conversation.")
    history = st.container(height=400)
    with history:
        for message in st.session_state["messages"]:
            avatar = "🧑‍💻"
            if message["role"] == "assistant":
                avatar = MODEL_AVATAR_URL
            with st.chat_message(message["role"], avatar=avatar):
                if message["content"] is not None:
                    st.markdown(message["content"])
                if message["error"] is not None:
                    st.error(message["error"],icon="🚨")
                if message["warning"] is not None:
                    st.warning(message["warning"],icon="⚠️")

    if prompt := st.chat_input("Type a message!", max_chars=5000):
        handle_user_input(prompt)
    st.markdown("\n") #add some space for iphone users
    gave_feedback = st.button('Give Feedback on Last Response', on_click=feedback)
    if gave_feedback: # TODO clean up the conditions here with a function
        st.session_state["feedback"].append("given") 
    else: 
        st.session_state["feedback"].append(None)
        

with st.sidebar:
    with st.container():
        st.title("Examples")
        for prompt in EXAMPLE_PROMPTS:
            st.button(prompt, args=(prompt,), on_click=handle_user_input)