What are Function Triggers in Azure?

An Azure Function Trigger is a part of a function’s stack that tells Azure how the function is invoked. The most common function triggers are HTTP, Timer, and Blob:

The HTTP trigger tells Azure that the function will be invoked through an HTTP request. An example is a GET request used to obtain the most recent transactions in a banking app.
The Timer trigger tells Azure that the function should be executed at specific times. An example is a business app that generates sales reports by 6 pm daily.
Blob storage describes a function whose logic is executed when a file is uploaded or updated in an Azure Blob Storage instance.

Trigger types

There are other trigger types aside from HTTP, Timer, and Blob:

Type	Purpose
Timer	Execute a function at a set interval.
HTTP	Execute a function when an HTTP request is received.
Blob	Execute a function when a file is uploaded or updated in Azure Blob storage.
Queue	Execute a function when a message is added to an Azure Storage queue.
Azure Cosmos DB	Execute a function when a document changes in a collection.
Event Hub	Execute a function when an event hub receives a new event.

index.js

function.json

const axios = require('axios');
const LIFX = require('lifx-http-api');
let client = new LIFX({
  bearerToken: process.env.LIFX_TOKEN
});
module.exports = function (context, myTimer) {
  // build up the DarkSky endpoint
  let endpoint = `${process.env.DS_API}/${process.env.DS_SECRET}/${
    process.env.LAT
    },${process.env.LNG}`;
  // use axios to call DarkSky for weather
  axios
    .get(endpoint)
    .then(data => {
      let temp = Math.round(data.data.currently.temperature);
      // make sure the temp isn't above 100 because that's as high as we can go
      temp = temp < 100 ? temp : 100;
      // determine the hue
      let hue = 200 + (160 * (temp / 100));
      // return Promise.all so we can resolve at the top level
      return Promise.all([
        data,
        client.setState('all', { color: `hue:${hue}` })
      ]);
    })
    .then(result => {
      // result[0] contains the darksky result
      // result[1] contains the LIFX result
      context.log(result[1]);
    })
    .catch(err => {
      context.log(err.message);
    });
};

HTTP triggers

HTTP triggers execute function logic when they receive a HTTP request. Examples of HTTP requests are:

GET request for requesting data
POST request for creating resources
PUT request for modifying resources
DELETE requests for deleting resources

Several HTTP verb handlers can be contained in a function. This means that an entire application can be composed of serverless functions.

A sample HTTP trigger function is given below. It is similar to the typical express routing handler function, however, the serverless function below uses an HTTP post request to submit a link to a given subreddit:

index.js

function.json

submit-link.js

const axios = require('axios')
const URL = 'https://oauth.reddit.com/api/submit'
const submitLink = async data => {
  /* 
    sr: name of a subreddit
    title: title of the submission. up to 300 characters long
    url: a valid URL
    api_type: the string json
    kind: one of (link, self, image, video, videogif)
    resubmit: boolean
  */
  const link = {
    title: data.title,
    sr: data.sr,
    url: data.url,
    api_type: 'json',
    kind: 'link',
  }
  const response = await axios({
    url: URL,
    method: 'post',
    headers: {
      Authorization: `bearer ${process.env.REDDIT_KEY}`,
      'user-agent': 'node.js',
    },
    params: link,
  })
  return response.data
}
module.exports = submitLink

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)

Learn in-demand tech skills in half the time

PRODUCTS

Mock Interview

New

Courses

Skill Paths

Projects

Assessments

What are Function Triggers in Azure?

Trigger types

Timer triggers

LIFX bulb example

Uses of time triggers

HTTP triggers

Blob triggers

Other trigger types