PyTorch Levels Up Its Serving Game with TorchServe

Logo of Facebook's PyTorch software

With TorchServe, Facebook and AWS continue to narrow the gap between machine learning research and production.

In recent years, PyTorch has largely overtaken Tensorflow as the machine learning model training framework that is preferred for research-leaning data scientists. There are a few reasons for this, but mainly that Pytorch is built for Python as its first-class language of use, whereas Tensorflow’s architecture stays much closer to its C/C++ core. Although both frameworks do have C/C++ cores, Pytorch does loads more to make its interface “pythonic“. For those unfamiliar with the term, it basically means the code is easy to understand and doesn’t make you feel like an adversarial teacher wrote it for an exam question.

Pytorch’s cleaner interface has resulted in mass adoption for folks whose main priority is to quickly turn their planned analyses into actionable results. We don’t have time to play with a static computation graph API that makes me feel like a criminal for wanting to place a breakpoint to debug a tensor’s value. We need to prototype something and get moving onto the next experiment.

It’s Not All Sunshine & Rainbows

However, this advantage comes at a cost. With Pytorch, we can easily churn through experiment after experiment, tossing results over the fence to be put into production at a similar speed. Sadly, getting these models serving in production has been slower than the experimentation throughput due to a lack of production-ready frameworks that encapsulate away API complexity. At least, these frameworks have been missing for Pytorch.

Tensorflow has long had a truly impressive model serving framework, TFX. Truthfully, there’s not much missing in its framework, provided that you are knee-deep in the Tensorflow ecosystem. If you have a TF model and are using Google Cloud, use TFX until it breathes its last breath. If you are not in that camp, combining TFX and PyTorch has been anything but plug and play.

A New Hope

Fear no more! PyTorch’s 1.5 release brings the initial version of TorchServe as well as experimental support of TorchElastic with Kubernetes for large-scale model training. Software powerhouses Facebook and AWS continue to supercharge PyTorch’s capabilities and provide a competitive alternative to Google’s Tensorflow-based software pipelines.

TorchServe is a flexible and easy-to-use library for serving PyTorch models in production performantly at scale. It is cloud and environment agnostic and supports features such as multi-model serving, logging, metrics, and the creation of RESTful endpoints for application integration.

PyTorch Docs

Let’s parse some of those qualities because they’re worth a focused repetition:

  • Serve PyTorch models in production performantly at scale
  • Cloud and environment agnostic
  • Multi-model serving
  • Logging
  • Metrics
  • RESTful endpoints

Any ML model in production that has these characteristics is bound to make your fellow engineers very happy.

Let’s TorchServe DenseNet

TorchServe provides most things you’d expect from a serving API right out of the box. On top of that, it additionally offers default inference handlers for image-based and text-based models. Due to my audio background, I’d be remiss to not slip in my complaint that once again audio-based models are left out of first-class support. Audio remains the black sheep in the machine learning world for now! Alas, I digress…

The DenseNet architecture, which yields good results on image classification tasks, is provided as a default model in TorchServe. The PyTorch engineers provide a pre-built docker image, but I added a few things to it for the demonstration below. If you want to re-create for yourself, run the four commands here.

Up and Running

With a few passed command-line arguments to the torchserve command, we have a production-ready service ready to provide model predictions. Without bogging down the article with the nitty-gritty, you can use a quick driver script to pump an image through the server from either a URL or local path.

Cliche time! Cats and dogs, here we go.

./query.sh images/puppy.jpg
A Blenheim spaniel puppy lying down on a white comforter.
Photo by GDragon612 on Fanpop

Blenheim_spaniel: 97.00%

Papillon: 1.40%

Japanese_spaniel: 0.94%

Brittany_spaniel: 0.41%

Spot on! Three of the top four as spaniel sub-breeds, and around 1% of the not-so-different papillon breed isn’t anything to clamor about.

How about a teeny tiny kitten, but with an extra fur hat on? I guess his natural fur and ears weren’t good enough for the photo? Regardless, surely this won’t change too much as far as the network’s predictions…

./query.sh images/kitten-2.jpg
An orange tabby kitten stands upright on its hind legs with a fur hat on its head.
Photo by sillymonkeyart on eBay

Egyptian_cat: 24.90%

Marmoset: 20.75%

Tabby: 11.22%

Patas: 10.17%

Well then…

There’s certainly a majority vote in the top 4 for cats, but the predictions barely edge out the Marmoset and Patas predictions, which are both classifications for…monkeys.

A Marmoset monkey [source]
A Patas monkey [source]

Not as cute.

Ok, one more! How about Troy Polamalu, a former NFL player whose hair at one point was insured for $1 million by the company Head and Shoulders?

./query.sh images/polamalu-hair.jpg
Former NFL player Roy Polamalu sites on a chair with his curly hair completely puffed out.
That's a lot of hair (AP Photo/Procter & Gamble, Bob Riha Jr.)

Sarong: 31.01%

Miniskirt: 27.77%

Wig: 20.82%

Neck_brace: 4.00%

Well…A for effort, I guess. Having a decent chunk of belief in the presence of a wig definitely makes sense. I wonder whether it’s the tights, the total, or something about the ridiculousness of the hair that causes the sarong and mini-skirt predictions. For the curious, now’s a great chance to apply attention techniques to debug what parts of the image were used heavily in influencing the classification.

TorchServe In Action

One step lower, here’s a demo of some raw cURL commands. Keep in mind, all of this API behavior came out of the box. All I provided was the choice of model and the input image.

Driving a local TorchServe instance

Conclusion

I’ve barely touched the surface of TorchServe, and that’s a good thing. If I could demonstrate all of its functionality in a simple blog post, it would be nowhere near production ready. Maybe allow a few more versions to turn over before putting it behind anything mission-critical. But Facebook and AWS have set an exciting foundation for greasing the skids between PyTorch-based research and production.

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