Example

Create APIs that process your workloads asynchronously.

Implementation

Create a folder for your API. In this case, we are deploying an iris-classifier AsyncAPI. This folder will have the following structure:

./iris-classifier
├── cortex.yaml
├── predictor.py
└── requirements.txt

We will now create the necessary files:

mkdir iris-classifier && cd iris-classifier
touch predictor.py requirements.txt cortex.yaml

# predictor.py

import os
import pickle
from typing import Dict, Any

import boto3
from botocore import UNSIGNED
from botocore.client import Config

labels = ["setosa", "versicolor", "virginica"]


class PythonPredictor:
    def __init__(self, config):
        if os.environ.get("AWS_ACCESS_KEY_ID"):
            s3 = boto3.client("s3")  # client will use your credentials if available
        else:
            s3 = boto3.client("s3", config=Config(signature_version=UNSIGNED))  # anonymous client

        s3.download_file(config["bucket"], config["key"], "/tmp/model.pkl")
        self.model = pickle.load(open("/tmp/model.pkl", "rb"))

    def predict(self, payload: Dict[str, Any]) -> Dict[str, str]:
        measurements = [
            payload["sepal_length"],
            payload["sepal_width"],
            payload["petal_length"],
            payload["petal_width"],
        ]

        label_id = self.model.predict([measurements])[0]

        # result must be json serializable
        return {"label": labels[label_id]}

# requirements.txt

boto3

# text_generator.yaml

- name: iris-classifier
  kind: AsyncAPI
  predictor:
    type: python
    path: predictor.py

Deploy

We can now deploy our API with the cortex deploy command. This command can be re-run to update your API configuration or predictor implementation.

cortex deploy cortex.yaml

# creating iris-classifier (AsyncAPI)
#
# cortex get                  (show api statuses)
# cortex get iris-classifier  (show api info)

Monitor

To check whether the deployed API is ready, we can run the cortex get command with the --watch flag.

cortex get iris-classifier --watch

# status     up-to-date   requested   last update
# live       1            1           10s
#
# endpoint: http://<load_balancer_url>/iris-classifier
#
# api id                                                         last deployed
# 6992e7e8f84469c5-d5w1gbvrm5-25a7c15c950439c0bb32eebb7dc84125   10s

Submit a workload

Now we want to submit a workload to our deployed API. We will start by creating a file with a JSON request payload, in the format expected by our iris-classifier predictor implementation.

This is the JSON file we will submit to our iris-classifier API.

# sample.json
{
    "sepal_length": 5.2,
    "sepal_width": 3.6,
    "petal_length": 1.5,
    "petal_width": 0.3
}

Once we have our sample request payload, we will submit it with a POST request to the endpoint URL previously displayed in the cortex get command. We will quickly get a request id back.

curl -X POST http://<load_balancer_url>/iris-classifier -H "Content-Type: application/json" -d '@./sample.json'

# {"id": "659938d2-2ef6-41f4-8983-4e0b7562a986"}

Retrieve the result

The obtained request id will allow us to check the status of the running payload and retrieve its result. To do so, we submit a GET request to the same endpoint URL with an appended /<id>.

curl http://<load_balancer_url>/iris-classifier/<id>  # <id> is the request id that was returned in the previous POST request

# {
#   "id": "659938d2-2ef6-41f4-8983-4e0b7562a986",
#   "status": "completed",
#   "result": {"label": "setosa"},
#   "timestamp": "2021-03-16T15:50:50+00:00"
# }

Depending on the status of your workload, you will get different responses back. The possible workload status are in_queue | in_progress | failed | completed. The result and timestamp keys are returned if the status is completed.

It is also possible to setup a webhook in your predictor to get the response sent to a pre-defined web server once the workload completes or fails. You can read more about it in the webhook documentation.

Stream logs

If necessary, you can stream the logs from a random running pod from your API with the cortex logs command. This is intended for debugging purposes only. For production logs, you can view the logs in cloudwatch logs.

cortex logs iris-classifier

Delete the API

Finally, you can delete your API with a simple cortex delete command.

cortex delete iris-classifier