🕸️ A Simple Proxy for Azure and OpenAI raised our GPT4 TPM limit by 24x

William Zeng - October 26th, 2023

OpenAI API rate limits are restrictive, with a top rate limit of 20K TPM for GPT4.
Even the most basic AI Agents make 3+ calls per request, and to effectively plan they’ll need to use RAG(retrieval augmented generation) (opens in a new tab). A minimally useful request should require an input of at least 500 tokens(~375 words ~ 2 paragraphs) worth of text, and generate roughly 125 tokens(half a paragraph?) of output.

Over a single request this equates to 1,875(3 * 625) tokens, hitting the token limit with 10.67 requests/min.
For reference, a Sweep ticket makes 20 GPT4 calls consuming an average of 2000 tokens and a total usage of 40,000 tokens.
This leads to a "Sweep" request limit of 0.5 requests/min, needing 2 minutes to finish a single request.
There’s a solution though.

Microsoft Azure East US has a 20K TPM limit for us.

We can use a proxy like(https://github.com/diemus/azure-openai-proxy (opens in a new tab)) to load the balance between OpenAI and Azure, bringing our total TPM limit from 20k → 40k.

This helps, but it only brings us up to 40k total TPM. Even better, we can balance between multiple Azure regions to further increase our rate limit.

Here’s a table of the rate limits we found on each region:

Azure Region	GPT-4 Rate Limit(TPM)
East Canada	100K
Japan East	100K
East US 2	100K
UK South	100K
Australia East	40K
Switzerland North	40K (dynamic)
East US	20K
France Central	20K
Sweden Central	NA
West Europe	NA
North Central US	NA
Total	480K/520K(dynamic)

Using all of the Azure regions, we were able to increase our TPM rate limit from 20k → 40k(2x increase!) → 480K(24x increase!!)

Here’s a graph of our OpenAI usage before/after this change:

Here's the code:

Sweep's OpenAI Proxy

import random
 
import openai
from loguru import logger
 
from sweepai.config.server import (
    AZURE_API_KEY,
    MULTI_REGION_CONFIG,
    OPENAI_API_BASE,
    OPENAI_API_ENGINE_GPT4,
    OPENAI_API_ENGINE_GPT4_32K,
    OPENAI_API_ENGINE_GPT35,
    OPENAI_API_KEY,
    OPENAI_API_TYPE,
    OPENAI_API_VERSION,
)
 
 
class OpenAIProxy:
    def __init__(self):
        pass
 
    def call_openai(self, model, messages, max_tokens, temperature) -> str:
        try:
            engine = None
            if (
                model == "gpt-3.5-turbo-16k"
                or model == "gpt-3.5-turbo-16k-0613"
                and OPENAI_API_ENGINE_GPT35 is not None
            ):
                engine = OPENAI_API_ENGINE_GPT35
            elif (
                model == "gpt-4"
                or model == "gpt-4-0613"
                and OPENAI_API_ENGINE_GPT4 is not None
            ):
                engine = OPENAI_API_ENGINE_GPT4
            elif (
                model == "gpt-4-32k"
                or model == "gpt-4-32k-0613"
                and OPENAI_API_ENGINE_GPT4_32K is not None
            ):
                engine = OPENAI_API_ENGINE_GPT4_32K
            if OPENAI_API_TYPE is None or engine is None:
                openai.api_key = OPENAI_API_KEY
                openai.api_base = "https://api.openai.com/v1"
                openai.api_version = None
                openai.api_type = "open_ai"
                logger.info(f"Calling {model} on OpenAI.")
                response = openai.ChatCompletion.create(
                    model=model,
                    messages=messages,
                    max_tokens=max_tokens,
                    temperature=temperature,
                )
                return response["choices"][0].message.content
            # validity checks for MULTI_REGION_CONFIG
            if (
                MULTI_REGION_CONFIG is None
                or not isinstance(MULTI_REGION_CONFIG, list)
                or len(MULTI_REGION_CONFIG) == 0
                or not isinstance(MULTI_REGION_CONFIG[0], list)
            ):
                logger.info(
                    f"Calling {model} with engine {engine} on Azure url {OPENAI_API_BASE}."
                )
                openai.api_type = OPENAI_API_TYPE
                openai.api_base = OPENAI_API_BASE
                openai.api_version = OPENAI_API_VERSION
                openai.api_key = AZURE_API_KEY
                response = openai.ChatCompletion.create(
                    engine=engine,
                    model=model,
                    messages=messages,
                    max_tokens=max_tokens,
                    temperature=temperature,
                )
                return response["choices"][0].message.content
            # multi region config is a list of tuples of (region_url, api_key)
            # we will try each region in order until we get a response
            # randomize the order of the list
            SHUFFLED_MULTI_REGION_CONFIG = random.sample(
                MULTI_REGION_CONFIG, len(MULTI_REGION_CONFIG)
            )
            for region_url, api_key in SHUFFLED_MULTI_REGION_CONFIG:
                try:
                    logger.info(
                        f"Calling {model} with engine {engine} on Azure url {region_url}."
                    )
                    openai.api_key = api_key
                    openai.api_base = region_url
                    openai.api_version = OPENAI_API_VERSION
                    openai.api_type = OPENAI_API_TYPE
                    response = openai.ChatCompletion.create(
                        engine=engine,
                        model=model,
                        messages=messages,
                        max_tokens=max_tokens,
                        temperature=temperature,
                    )
                    return response["choices"][0].message.content
                except SystemExit:
                    raise SystemExit
                except Exception as e:
                    logger.exception(f"Error calling {region_url}: {e}")
            raise Exception("No Azure regions available")
        except SystemExit:
            raise SystemExit
        except Exception as e:
            if OPENAI_API_KEY:
                try:
                    openai.api_key = OPENAI_API_KEY
                    openai.api_base = "https://api.openai.com/v1"
                    openai.api_version = None
                    openai.api_type = "open_ai"
                    logger.info(f"Calling {model} with OpenAI.")
                    response = openai.ChatCompletion.create(
                        model=model,
                        messages=messages,
                        max_tokens=max_tokens,
                        temperature=temperature,
                    )
                    return response["choices"][0].message.content
                except SystemExit:
                    raise SystemExit
                except Exception as _e:
                    logger.error(f"OpenAI API Key found but error: {_e}")
            logger.error(f"OpenAI API Key not found and Azure Error: {e}")
            raise e

MULTI_REGION_CONFIG is a list of tuples of (region_url, api_key) that we randomize over, and the other envvars are standard strings from OpenAI/Azure. Another requirement with our proxy is that each of the models(GPT3.5, GPT4, GPT4-32K) must have consistent naming across regions.

We have some potential improvements to our proxy:

We randomize between the different Azure regions uniformly, so this could be improved by weighted randomization.
We could decrease our expected latency further by keeping track of which regions have capacity.
We could optimize further by trying to estimate the load on each region. We can perform a smart optimization by computing a simple function like:
- estimated_latency = mean_over_regions((input_tokens + output_tokens) / latency_per_token_estimate)
- estimated_load = estimated_latency - true_latency
- and then optimize the region-level randomization by negatively weighting the estimated_load

Here's a link to our production code:
https://github.com/sweepai/sweep/blob/main/sweepai/utils/openai_proxy.py (opens in a new tab)

If you're looking for a more advanced version of this, check out LiteLLM's load balancer (opens in a new tab).

If you're interested in using Sweep/have questions about how we use LLMs in production, reach out at https://discord.gg/sweep (opens in a new tab)!

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