Refreshing Access Token

An example of how the authentication access token can be refreshed automatically.


When running integrations continuously, authentication towards the API must be refreshed periodically. By default, this must be done every hour and should happen automatically without interfering with the integration. In this example, a simple access token refresh routine that keeps the API authenticated has been implemented.


  • Service Account Credentials You must create and know the credentials of a Service Account. Any role will suffice.

  • OAuth2 This example heavily builds on the OAuth2 Authentication Guide. It is recommended that you understand this routine before attempting to expand upon it.

Example Code

The following points summarize the provided example code.

  • A simulated REST API call is triggered every 5 seconds.

  • An instance of the Auth class provides the access token as required.

  • If the access token is within 1 minute of expiration, the token is first refreshed.

Environment Setup

If you wish to run the code locally, make sure you have a working runtime environment.

The following packages are required by the example code and must be installed.

pip install pyjwt==2.7.0
pip install requests==2.31.0

Add the following credentials to your environment as they will be used to authenticate the API.



The following code snippet implements the token refresh routine.

import os
import time
import jwt       # pip install pyjwt==2.1.0
import requests  # pip install requests==2.25.1

# Constants for authentication credentials.
KEY_ID = os.environ.get('DT_SERVICE_ACCOUNT_KEY_ID', '')
SECRET = os.environ.get('DT_SERVICE_ACCOUNT_SECRET', '')
EMAIL = os.environ.get('DT_SERVICE_ACCOUNT_EMAIL', '')

class Auth():
    Handles automatic refresh of access token every
    time get_token() is called with a buffer of 1 minute.


    refresh_buffer = 60  # s
    auth_url = ''

    def __init__(self, key_id: str, email: str, secret: str):
        # Set attributes.
        self.key_id = key_id = email
        self.secret = secret

        # Initialize some variables.
        self.token = ''
        self.expiration = 0

    def refresh(self):
        # Construct the JWT header.
        jwt_headers = {
            'alg': 'HS256',
            'kid': self.key_id,

        # Construct the JWT payload.
        jwt_payload = {
            'iat': int(time.time()),         # current unixtime
            'exp': int(time.time()) + 3600,  # expiration unixtime
            'aud': self.auth_url,

        # Sign and encode JWT with the secret.
        encoded_jwt = jwt.encode(

        # Prepare HTTP POST request data.
        # note: The requests package applies Form URL-Encoding by default.
        request_data = {
            'assertion': encoded_jwt,
            'grant_type': 'urn:ietf:params:oauth:grant-type:jwt-bearer'

        # Exchange the JWT for an access token.
        access_token_response =
            headers={'Content-Type': 'application/x-www-form-urlencoded'},

        # Halt if response contains an error.
        if access_token_response.status_code != 200:
            print('Status Code: {}'.format(access_token_response.status_code))
            return None

        # Unpack the response dictionary.
        token_json = access_token_response.json()
        self.token = token_json['access_token']
        self.expiration = time.time() + token_json['expires_in']

    def get_token(self):
        # Check if access token needs a refresh. A 1 minute buffer is added.
        if self.expiration - time.time() < self.refresh_buffer:
            # Print expiration message to console.

            # Fetch a brand new access token and expiration.

        # Print time until expiration.
        print('Token expires in {}s.'.format(
            int(self.expiration - time.time() - self.refresh_buffer),

        # Return the token to user.
        return self.token

def function_that_calls_rest_api(access_token: str):
    # This would usually do something useful.

if __name__ == '__main__':
    # Initialize an authentication object.
    auth = Auth(KEY_ID, EMAIL, SECRET)

    # Do some task, here simulated by an infinite loop.
    while True:
        # Simulate some routine that needs authentication for the REST API.

Expected Output

For visualization purposes, an expiration timer is printed each time the token is used.

Token expires in 3538s.
Token expires in 3533s.
Token expires in 3528s.
Token expires in 13s.
Token expires in 8s.
Token expires in 3s.
Token expires in 3538s.
Token expires in 3533s

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