uBatch¶
uBatch is a simple, yet elegant library for processing streams data in micro batches.
uBatch allow to process multiple inputs data from different threads as a single block of data, this is useful when process data in a batches has a lower cost than processing it independently, for example process data in GPU or take advantage from optimization of libraries written in C. Ideally, the code that processes the batches should release the Python GIL for allowing others threads/coroutines to run, this is true in many C libraries wrapped in Python.
Example
>>> import threading
>>>
>>> from typing import List
>>> from ubatch import ubatch_decorator
>>>
>>>
>>> @ubatch_decorator(max_size=5, timeout=0.01)
... def squared(a: List[int]) -> List[int]:
... print(a)
... return [x ** 2 for x in a]
...
>>>
>>> inputs = list(range(10))
>>>
>>> # Run squared as usual
... _ = squared(inputs)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>>
>>>
>>> def thread_function(number: int) -> None:
... _ = squared.ubatch(number)
...
>>>
>>> # Multiple threads squared individual inputs
... threads = []
>>> for i in inputs:
... t = threading.Thread(target=thread_function, args=(i,))
... threads.append(t)
... t.start()
...
[0, 1, 2, 3, 4]
[5, 6, 7, 8, 9]
>>> for t in threads:
... t.join()
The example above shows 10 threads calculating the square of a number, using uBatch the threads delegate the calculation task to a single process that calculates them in batch.
Installing uBatch and Supported Versions¶
pip install ubatch
uBatch officially supports Python 3.6+.
Why using uBatch¶
When data is processed offline it is easy to collect data to be processed at same time, the same does not happen when requests are attended online as example using Flask, this is where the uBatch potential comes in.
TensorFlow or Scikit-learn are just some of the libraries that can take advantage of this functionality.
uBatch and application server¶
Python application servers work like this:
When the server is initialized multiple processes are created and each process create a bunch of threads for handling requests. Taking advantage of those threads that run in parallel uBatch can be used to group several inputs and process them in a single block.
Let’s see a Flask example:
import numpy as np
from typing import List, Dict
from flask import Flask, request as flask_request
from flask_restx import Resource, Api
from ubatch import UBatch
from model import load_model
app = Flask(__name__)
api = Api(app)
model = load_model()
predict_batch: UBatch[np.array, np.array] = UBatch(max_size=50, timeout=0.01)
predict_batch.set_handler(handler=model.batch_predict)
predict_batch.start()
@api.route("/predict")
class Predict(Resource):
def post(self) -> Dict[str, List[float]]:
received_input = np.array(flask_request.json["input"])
result = predict_batch.ubatch(received_input)
return {"prediction": result.tolist()}
Start application server:
gunicorn -k gevent app:app
Another example using uBatch to join multiple requests into one:
import requests
from typing import List, Dict
from flask import Flask, request as flask_request
from flask_restx import Resource, Api
from ubatch import ubatch_decorator
app = Flask(__name__)
api = Api(app)
FAKE_TITLE_MPI_URL = "http://my_mpi_url/predict"
@ubatch_decorator(max_size=100, timeout=0.03)
def batch_fake_title_post(titles: List[str]) -> List[bool]:
"""Post a list of titles to MPI and return responses in a list"""
# json_post example: {"predict": ["title1", "title2", "title3"]}
json_post = {"predict": titles}
# response example: {"predictions": [False, True. False]}
response = requests.post(FAKE_TITLE_MPI_URL, json=json_post).json()
# return: [False, True, False]
return [x for x in response["predictions"]]
@api.route("/predict")
class Predict(Resource):
def post(self) -> Dict[str, bool]:
# title example: "Title1"
title = flask_request.json["title"]
# prediction example: False
prediction = fake_title_batch.ubatch(title)
return {"prediction": prediction}
Start application server:
gunicorn -k gevent app:app
Start developing uBatch¶
Install poetry
curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python -
Clone repository
git clone git@github.com:mercadolibre/ubatch.git
Start shell and install dependencies
cd ubatch
poetry shell
poetry install
Run tests
pytest
Building docs
cd ubatch/docs
poetry shell
make html