"Serverless" and "BERT" are two topics that strongly influenced the world of computing.Serverless architectureallows us to provide dynamically scale-in and -out the software without managing and provisioning computing power.It allows us, developers, to focus on our applications.
BERT is probably the most known NLP model out there. You can say it changed the way we work with textual data and whatwe can learn from it."BERT will help [Google] Search [achieve a] better understand[ing] one in 10 searches".BERT and its fellow friends RoBERTa, GPT-2, ALBERT, and T5 will drive business and business ideas in the next few yearsand will change/disrupt business areas like the internet once did.
search language understanding BERT
Imagine the business value you achieve combining these two together. But BERT is not the easiest machine learning modelto be deployed in a serverless architecture. BERT is quite big and needs quite some computing power. Most tutorials youfind online demonstrate how to deploy BERT in "easy" environments like a VM with 16GB of memory and 4 CPUs.
I will show you how to leverage the benefits of serverless architectures and deploy a BERT Question-Answering API in aserverless environment. We are going to use the Transformers library byHuggingFace, the Serverless Framework, and AWS Lambda.
Transformer Library by Huggihttps://www.philschmid.de/static/blog/serverless-bert-with-huggingface-and-aws-lambda/transformers-logo.pngbda/transformers-logo.png" alt="transformers-logo">
The Transformers library provides state-of-the-art machine learningarchitectures like BERT, GPT-2, RoBERTa, XLM, DistilBert, XLNet, T5 for Natural Language Understanding (NLU) and NaturalLanguage Generation (NLG). It also provides thousands of pre-trained models in 100+ different languages and is deeplyinteroperability between PyTorch & TensorFlow 2.0. It enables developers to fine-tune machine learning models fordifferent NLP-tasks like text classification, sentiment analysis, question-answering, or text generation.
AWS Lambda
AWS Lambda is a serverless computing service that lets yourun code without managing servers. It executes your code only when required and scales automatically, from a fewrequests per day to thousands per second. You only pay for the compute time you consume – there is no charghttps://www.philschmid.de/static/blog/serverless-bert-with-huggingface-and-aws-lambda/lambda-logo.pngrt-with-huggingface-and-aws-lambda/lambda-logo.png" alt="aws-lambda-logo">
Serverless Framework
The Serverless Framework helps us develop and deploy AWS Lambda functions. It’s a CLI that offers structure, automation,and best practices right out of the box. It also allows us to focus on building sophisticated, event-driven, serhttps://www.philschmid.de/static/blog/serverless-bert-with-huggingface-and-aws-lambda/serverless-logo.pngic/blog/serverless-bert-with-huggingface-and-aws-lambda/serverless-logo.png" alt="serverless-framework-logo">
If you aren’t familiar or haven’t set up the Serverless Framework, take a look atthis quick-start with the Serverless Framework.
Tutorial
Before we get started, make sure you have the Serverless Framework configured and set up. Youalso need a working Docker environment. A Docker environment is used to build our own python runtime, which we deploy toAWS Lambda. Furthermore, you need access to an AWS Account to create an S3 Bucket and the AWS Lambda function.
In the tutorial, we are going to build a Question-Answering API with a pre-trained BERT model. The idea is we send acontext (small paragraph) and a question to the lambda function, which will respond with the answer to the question.
As this guide is not about building a model, we will use a pre-built version, that I created using distilbert. You cancheck the colab notebook here.
context = """We introduce a new language representation model called BERT, which stands forBidirectional Encoder Representations from Transformers. Unlike recent languagerepresentation models (Peters et al., 2018a; Radford et al., 2018), BERT isdesigned to pretrain deep bidirectional representations from unlabeled text byjointly conditioning on both left and right context in all layers. As a result,the pre-trained BERT model can be finetuned with just one additional outputlayer to create state-of-the-art models for a wide range of tasks, such asquestion answering and language inference, without substantial taskspecificarchitecture modifications. BERT is conceptually simple and empiricallypowerful. It obtains new state-of-the-art results on eleven natural languageprocessing tasks, including pushing the GLUE score to 80.5% (7.7% point absoluteimprovement), MultiNLI accuracy to 86.7% (4.6% absolute improvement), SQuAD v1.1question answering Test F1 to 93.2 (1.5 point absolute improvement) and SQuADv2.0 Test F1 to 83.1 (5.1 point absolute improvement).""" question_one = "What is BERTs best score on Squadv2 ?"# 83 . 1 question_two = "What does the 'B' in BERT stand for?"# 'bidirectional encoder representations from transformers'Before we start, I want to say that we're not gonna go into detail this time. If you want to understand more about howto use Deep Learning in AWS Lambda I suggest you check ouhttps://www.philschmid.dehttps://www.philschmid.de/static/blog/serverless-bert-with-huggingface-and-aws-lambda/architektur.png this.

What are we going to do:
- create a Python Lambda function with the Serverless Frameworkcreate an S3 Bucket and upload our modelConfigure the
serverless.yaml, add transformers as a dependency and set up an API Gateway for inferenceadd the BERT model from thecolab notebookto our functiondeploy & test the functionYou can find everything we are doing in thisGitHub repositoryand thecolab notebook.
Create a Python Lambda function
First, we create our AWS Lambda function by using the Serverless CLI with the aws-python3 template.
serverless create --template aws-python3 --path serverless-bertThis CLI command will create a new directory containing a handler.py, .gitignore and serverless.yaml file. Thehandler.py contains some basic boilerplate code.
import json def hello(event, context): body = { "message": "Go Serverless v1.0! Your function executed successfully!", "input": event } response = { "statusCode": 200, "body": json.dumps(body) } return responseAdd transformers as a dependency
The Serverless Framework created almost anything we need, except for the requirements.txt. We create therequirements.txt by hand and add the following dependencies.
https://download.pytorch.org/whl/cpu/torch-1.5.0%2Bcpu-cp38-cp38-linux_x86_64.whltransformers==2.10Create an S3 Bucket and upload the model
AWS S3 and Pytorch provide a unique way of working with machine learning models which are bigger than 250MB. Why 250 MB?The size of the Lambda function is limited to 250MB unzipped.
But S3 allows files to be loaded directly from S3 into memory. In our function, we are going to load our modelsquad-distilbert from S3 into memory and reading it from memory as a buffer in Pytorch.
If you run thecolab notebookit will create a file called squad-distilbert.tar.gz, which includes our model.
For creating an S3 Bucket you can either create one using the management console or with this command.
aws s3api create-bucket --bucket bucket-name --region eu-central-1 --create-bucket-configuration LocationConstraint=eu-central-1After we created the bucket we can upload our model. You can do it either manually or using the provided python script.
import boto3 def upload_model(model_path='', s3_bucket='', key_prefix='', aws_profile='default'): s3 = boto3.session.Session(profile_name=aws_profile) client = s3.client('s3') client.upload_file(model_path, s3_bucket, key_prefix)Configuring the serverless.yaml
This time I provided the complete serverless.yamlfor us. If you want to know what each section is used for, I suggestyou check outScaling Machine Learning from ZERO to HERO. Inthis article, I went through each configuration and explain the usage of them.
service: serverless-bert provider: name: aws runtime: python3.8 region: eu-central-1 timeout: 60 iamRoleStatements: - Effect: 'Allow' Action: - s3:getObject Resource: arn:aws:s3:::<your-S3-Bucket>/<key_prefix>/* custom: pythonRequirements: dockerizePip: true zip: true slim: true strip: false noDeploy: - docutils - jmespath - pip - python-dateutil - setuptools - six - tensorboard useStaticCache: true useDownloadCache: true cacheLocation: './cache'package: individually: false exclude: - package.json - package-log.json - node_modules/** - cache/** - test/** - __pycache__/** - .pytest_cache/** - model/pytorch_model.bin - raw/** - .vscode/** - .ipynb_checkpoints/** functions: predict_answer: handler: handler.predict_answer memorySize: 3008 timeout: 60 events: - http: path: ask method: post cors: true plugins: - serverless-python-requirementsAdd the BERT model from the colab notebook to our function
A typical transformers model consists of a pytorch_model.bin, config.json, special_tokens_map.json,tokenizer_config.json, and vocab.txt. Thepytorch_model.bin has already been extracted and uploaded to S3.
We are going to add config.json, special_tokens_map.json, tokenizer_config.json, and vocab.txt directly into ourLambda function because they are only a few KB in size. Therefore we create a model directory in our lambda function.
If this sounds complicated, check out theGitHub repository.
The next step is to create a model.py in the model/ directory that holds our model class ServerlessModel.
from transformers import AutoModelForQuestionAnswering, AutoTokenizer, AutoConfigimport torchimport boto3import osimport tarfileimport ioimport base64import jsonimport re s3 = boto3.client('s3') class ServerlessModel: def __init__(self, model_path=None, s3_bucket=None, file_prefix=None): self.model, self.tokenizer = self.from_pretrained( model_path, s3_bucket, file_prefix) def from_pretrained(self, model_path: str, s3_bucket: str, file_prefix: str): model = self.load_model_from_s3(model_path, s3_bucket, file_prefix) tokenizer = self.load_tokenizer(model_path) return model, tokenizer def load_model_from_s3(self, model_path: str, s3_bucket: str, file_prefix: str): if model_path and s3_bucket and file_prefix: obj = s3.get_object(Bucket=s3_bucket, Key=file_prefix) bytestream = io.BytesIO(obj['Body'].read()) tar = tarfile.open(fileobj=bytestream, mode="r:gz") config = AutoConfig.from_pretrained(f'{model_path}/config.json') for member in tar.getmembers(): if member.name.endswith(".bin"): f = tar.extractfile(member) state = torch.load(io.BytesIO(f.read())) model = AutoModelForQuestionAnswering.from_pretrained( pretrained_model_name_or_path=None, state_dict=state, config=config) return model else: raise KeyError('No S3 Bucket and Key Prefix provided') def load_tokenizer(self, model_path: str): tokenizer = AutoTokenizer.from_pretrained(model_path) return tokenizer def encode(self, question, context): encoded = self.tokenizer.encode_plus(question, context) return encoded["input_ids"], encoded["attention_mask"] def decode(self, token): answer_tokens = self.tokenizer.convert_ids_to_tokens( token, skip_special_tokens=True) return self.tokenizer.convert_tokens_to_string(answer_tokens) def predict(self, question, context): input_ids, attention_mask = self.encode(question, context) start_scores, end_scores = self.model(torch.tensor( [input_ids]), attention_mask=torch.tensor([attention_mask])) ans_tokens = input_ids[torch.argmax( start_scores): torch.argmax(end_scores)+1] answer = self.decode(ans_tokens) return answerIn the handler.py we create an instance of our ServerlessModel and can use the predict function to get our answer.
try: import unzip_requirementsexcept ImportError: passfrom model.model import ServerlessModelimport json model = ServerlessModel('./model', <s3_bucket>, <file_prefix>) def predict_answer(event, context): try: body = json.loads(event['body']) answer = model.predict(body['question'], body['context']) return { "statusCode": 200, "headers": { 'Content-Type': 'application/json', 'Access-Control-Allow-Origin': '*', "Access-Control-Allow-Credentials": True }, "body": json.dumps({'answer': answer}) } except Exception as e: return { "statusCode": 500, "headers": { 'Content-Type': 'application/json', 'Access-Control-Allow-Origin': '*', "Access-Control-Allow-Credentials": True }, "body": json.dumps({"error": repr(e)}) }Deploy & Test the function
In order to deploy the function you only have https://www.philschmid.dehttps://www.philschmid.de/static/blog/serverless-bert-with-huggingface-and-aws-lambda/serverless-deployment.png something like this.

Test and Outcome
To test our Lambda function we can use Insomnia, Postman, or any other REST client. Just add a JSON with a context anda question to the body of your request. Let´s try it with our example from the colab notebook.
{ "context": "We introduce a new language representation model called BERT, which stands for idirectional Encoder Representations from Transformers. Unlike recent language epresentation models (Peters et al., 2018a; Radford et al., 2018), BERT is designed to pretrain deep bidirectional representations from unlabeled text by jointly conditioning on both left and right context in all layers. As a result, the pre-trained BERT model can be finetuned with just one additional output layer to create state-of-the-art models for a wide range of tasks, such as question answering and language inference, without substantial taskspecific architecture modifications. BERT is conceptually simple and empirically powerful. It obtains new state-of-the-art results on eleven natural language processing tasks, including pushing the GLUE score to 80.5% (7.7% point absolute improvement), MultiNLI accuracy to 86.7% (4.6% absolute improvement), SQuAD v1.1 question answering Test F1 to 93.2 (1.5 point absolute improvement) and SQuAD v2.0 Test F1 to 83.1 (5.1 point absolute improvement).", "question":https://www.philschmid.dehttps://www.philschmid.de/static/blog/serverless-bert-with-huggingface-and-aws-lambda/insomnia-request.pngne="">}
Our ServerlessModel answered our question correctly with 83.1. Also, you can see the complete request took 319mswith a lambda execution time of around 530ms. To be honest, this is pretty fast.
The best thing is, our BERT model automatically scales up if there are several incoming requests! It scales up tothousands of parallel requests without any worries.
If you rebuild this, you have to be careful that the first request could take a while. First off, the Lambda isunzipping and installing our dependencies and then downloading the model from S3.
Thanks for reading. You can find theGitHub repository with the complete codehere and the colab notebookhere.
Thanks for reading. If you have any questions, feel free to contact me or comment this article. You can also connectwith me on Twitter orLinkedIn.
