Python client library starter

Follow this step-by-step tutorial to build an Internet-of-Things (IoT) application with InfluxData client libraries and your favorite framework or language.

In this tutorial, you’ll use the InfluxDB API and client libraries to build a modern application as you learn the following:

• InfluxDB core concepts.

• How the application interacts with devices and InfluxDB.

• How to authenticate apps and devices to the API.

• How to install a client library.

• How to write and query data in InfluxDB.

• How to use the InfluxData UI libraries to format data and create visualizations.

Contents

• Contents
• Set up InfluxDB
  • Authenticate with an InfluxDB API token
• Introducing IoT Starter
• Create the application
• Install InfluxDB client library
• Configure the client library
• Build the API
• Create the API to register devices
  • Create an authorization for the device
  • Write the device authorization to a bucket
• Create the API to list devices
• Create IoT virtual device
• Write telemetry data
• Query telemetry data
• Define API responses
• Install and run the UI

Set up InfluxDB

If you haven’t already, create an InfluxDB Cloud account or install InfluxDB OSS.

Authenticate with an InfluxDB API token

For convenience in development, create an All Access token for your application. This grants your application full read and write permissions on all resources within your InfluxDB organization.

Introducing IoT Starter

The application architecture has four layers:

• InfluxDB API: InfluxDB v2 API.
• IoT device: Virtual or physical devices write IoT data to the InfluxDB API.
• UI: Sends requests to the server and renders views in the browser.
• API: Receives requests from the UI, sends requests to InfluxDB, and processes responses from InfluxDB.

Create the application

Create a directory that will contain your iot-api projects. The following example code creates an iot-api directory in your home directory and changes to the new directory:

mkdir ~/iot-api-apps
cd ~/iot-api-apps

Use Flask, a lightweight Python web framework, to create your application.

1. In your ~/iot-api-apps directory, open a terminal and enter the following commands to create and navigate into a new project directory:

   mkdir iot-api-python && cd $_
   

2. Enter the following commands in your terminal to create and activate a Python virtual environment for the project:

   # Create a new virtual environment named "virtualenv"
   # Python 3.8+
   python -m venv virtualenv
   
   # Activate the virtualenv (OS X & Linux)
   source virtualenv/bin/activate
   

3. After activation completes, enter the following commands in your terminal to install Flask with the pip package installer (included with Python):

   pip install Flask
   

4. In your project, create a app.py file that:

   1. Imports the Flask package.
   2. Instantiates a Flask application.
   3. Provides a route to execute the application.

   from flask import Flask
   app = Flask(__name__)
   
   @app.route("/")
   def hello():
     return "Hello World!"
   

   influxdata/iot-api-python app.py

   Start your application. The following example code starts the application on http://localhost:3001 with debugging and hot-reloading enabled:

   export FLASK_ENV=development
   flask run -h localhost -p 3001
   

   In your browser, visit http://localhost:3001 to view the “Hello World!” response.

Install InfluxDB client library

The InfluxDB client library provides the following InfluxDB API interactions:

• Query data with the Flux language.
• Write data to InfluxDB.
• Batch data in the background.
• Retry requests automatically on failure.

Enter the following command into your terminal to install the client library:

pip install influxdb-client

For more information about the client library, see the influxdata/influxdb-client-python repo.

Configure the client library

InfluxDB client libraries require configuration properties from your InfluxDB environment. Typically, you’ll provide the following properties as environment variables for your application:

• INFLUX_URL
• INFLUX_TOKEN
• INFLUX_ORG
• INFLUX_BUCKET
• INFLUX_BUCKET_AUTH

To set up the client configuration, create a config.ini in your project’s top level directory and paste the following to provide the necessary InfluxDB credentials:

[APP]
INFLUX_URL = <INFLUX_URL>
INFLUX_TOKEN = <INFLUX_TOKEN>
INFLUX_ORG = <INFLUX_ORG_ID>
INFLUX_BUCKET = iot_center
INFLUX_BUCKET_AUTH = iot_center_devices

Replace the following:

• <INFLUX_URL>: your InfluxDB instance URL.
• <INFLUX_TOKEN>: your InfluxDB API token with permission to query (read) buckets and create (write) authorizations for devices.
• <INFLUX_ORG_ID>: your InfluxDB organization ID.

Build the API

Your application API provides server-side HTTP endpoints that process requests from the UI. Each API endpoint is responsible for the following:

1. Listen for HTTP requests (from the UI).
2. Translate requests into InfluxDB API requests.
3. Process InfluxDB API responses and handle errors.
4. Respond with status and data (for the UI).

Create the API to register devices

In this application, a registered device is a point that contains your device ID, authorization ID, and API token. The API token and authorization permissions allow the device to query and write to INFLUX_BUCKET. In this section, you add the API endpoint that handles requests from the UI, creates an authorization in InfluxDB, and writes the registered device to the INFLUX_BUCKET_AUTH bucket. To learn more about API tokens and authorizations, see Manage API tokens

The application API uses the following /api/v2 InfluxDB API endpoints:

• POST /api/v2/query: to query INFLUX_BUCKET_AUTH for a registered device.
• GET /api/v2/buckets: to get the bucket ID for INFLUX_BUCKET.
• POST /api/v2/authorizations: to create an authorization for the device.
• POST /api/v2/write: to write the device authorization to INFLUX_BUCKET_AUTH.

Create an authorization for the device

In this section, you create an authorization with read-write permission to INFLUX_BUCKET and receive an API token for the device. The example below uses the following steps to create the authorization:

1. Instantiate the AuthorizationsAPI client and BucketsAPI client with the configuration.
2. Retrieve the bucket ID.
3. Use the client library to send a POST request to the /api/v2/authorizations InfluxDB API endpoint.

Create a ./api/devices.py file that contains the following:

# Import the dependencies.
import configparser
from datetime import datetime
from uuid import uuid4

# Import client library classes.
from influxdb_client import Authorization, InfluxDBClient, Permission, PermissionResource, Point, WriteOptions
from influxdb_client.client.authorizations_api import AuthorizationsApi
from influxdb_client.client.bucket_api import BucketsApi
from influxdb_client.client.query_api import QueryApi
from influxdb_client.client.write_api import SYNCHRONOUS

from api.sensor import Sensor

# Get the configuration key-value pairs.

config = configparser.ConfigParser()
config.read('config.ini')

def create_authorization(device_id) -> Authorization:
    influxdb_client = InfluxDBClient(url=config.get('APP', 'INFLUX_URL'),
                                     token=os.environ.get('INFLUX_TOKEN'),
                                     org=os.environ.get('INFLUX_ORG'))

    authorization_api = AuthorizationsApi(influxdb_client)
    # get bucket_id from bucket
    buckets_api = BucketsApi(influxdb_client)
    buckets = buckets_api.find_bucket_by_name(config.get('APP', 'INFLUX_BUCKET'))  # function returns only 1 bucket
    bucket_id = buckets.id
    org_id = buckets.org_id
    desc_prefix = f'IoTCenterDevice: {device_id}'
    org_resource = PermissionResource(org_id=org_id, id=bucket_id, type="buckets")
    read = Permission(action="read", resource=org_resource)
    write = Permission(action="write", resource=org_resource)
    permissions = [read, write]
    authorization = Authorization(org_id=org_id, permissions=permissions, description=desc_prefix)
    request = authorization_api.create_authorization(authorization)
    return request

To create an authorization that has read-write permission to INFLUX_BUCKET, you need the bucket ID. To retrieve the bucket ID, create_authorization(deviceId) calls the BucketsAPI find_bucket_by_name function that sends a GET request to the /api/v2/buckets InfluxDB API endpoint. create_authorization(deviceId) then passes a new authorization in the request body with the following:

• Bucket ID.
• Organization ID.
• Description: IoTCenterDevice: DEVICE_ID.
• List of permissions to the bucket.

To learn more about API tokens and authorizations, see Manage API tokens.

Next, write the device authorization to a bucket.

Write the device authorization to a bucket

With a device authorization in InfluxDB, write a point for the device and authorization details to INFLUX_BUCKET_AUTH. Storing the device authorization in a bucket allows you to do the following:

• Report device authorization history.
• Manage devices with and without tokens.
• Assign the same token to multiple devices.
• Refresh tokens.

To write a point to InfluxDB, use the InfluxDB client library to send a POST request to the /api/v2/write InfluxDB API endpoint. In ./api/devices.py, add the following create_device(device_id) function:

def create_device(device_id=None):
    influxdb_client = InfluxDBClient(url=config.get('APP', 'INFLUX_URL'),
                                     token=config.get('APP', 'INFLUX_TOKEN'),
                                     org=config.get('APP', 'INFLUX_ORG'))
    if device_id is None:
        device_id = str(uuid4())
    write_api = influxdb_client.write_api(write_options=SYNCHRONOUS)
    point = Point('deviceauth') \
        .tag("deviceId", device_id) \
        .field('key', f'fake_auth_id_{device_id}') \
        .field('token', f'fake_auth_token_{device_id}')
    client_response = write_api.write(bucket=config.get('APP', 'INFLUX_BUCKET_AUTH'), record=point)
    # write() returns None on success
    if client_response is None:
        return device_id
    # Return None on failure
    return None

create_device(device_id) takes a device_id and writes data to INFLUX_BUCKET_AUTH in the following steps:

1. Initialize InfluxDBClient() with url, token, and org values from the configuration.
2. Initialize a WriteAPI client for writing data to an InfluxDB bucket.
3. Create a Point.
4. Use write_api.write() to write the Point to the bucket.
5. Check for failures–if the write was successful, write_api returns None.
6. Return device_id if successful; None otherwise.

The function writes a point with the following elements:

Next, create the API to list devices.

Create the API to list devices

Add the /api/devices API endpoint that retrieves, processes, and lists registered devices.

1. Create a Flux query that gets the last row of each series that contains a deviceauth measurement. The example query below returns rows that contain the key field (authorization ID) and excludes rows that contain a token field (to avoid exposing tokens to the UI).

   // Flux query finds devices
    from(bucket:`${INFLUX_BUCKET_AUTH}`)
         |> range(start: 0)
         |> filter(fn: (r) => r._measurement == "deviceauth" and r._field != "token")
         |> last()
   

2. Use the QueryApi client to send the Flux query to the POST /api/v2/query InfluxDB API endpoint.

   In ./api/devices.py, add the following:

def get_device(device_id=None) -> {}:
    influxdb_client = InfluxDBClient(url=config.get('APP', 'INFLUX_URL'),
                                     token=os.environ.get('INFLUX_TOKEN'),
                                     org=os.environ.get('INFLUX_ORG'))
    # Queries must be formatted with single and double quotes correctly
    query_api = QueryApi(influxdb_client)
    device_filter = ''
    if device_id:
        device_id = str(device_id)
        device_filter = f'r.deviceId == "{device_id}" and r._field != "token"'
    else:
        device_filter = f'r._field != "token"'

    flux_query = f'from(bucket: "{config.get("APP", "INFLUX_BUCKET_AUTH")}") ' \
                 f'|> range(start: 0) ' \
                 f'|> filter(fn: (r) => r._measurement == "deviceauth" and {device_filter}) ' \
                 f'|> last()'
    
    response = query_api.query(flux_query)
    result = []
    for table in response:
        for record in table.records:
            try:
                'updatedAt' in record
            except KeyError:
                record['updatedAt'] = record.get_time()
                record[record.get_field()] = record.get_value()
            result.append(record.values)
    return result