Getting Started with Kloudless Webhooks

Introduction

There are times when your application needs to keep up with changes that take place in your users’ cloud storage. Perhaps your application needs to perform an action when new files appear, or needs to update its state when files are modified/deleted. Kloudless solves this problem by making an HTTP request (a “webhook“) to a URL you define, with information on which accounts have changed. You can then query the events endpoint for more detailed information on modified files in the account.

The first release of Kloudless’ events endpoint supports Dropbox, Box, OneDrive, Evernote, Sharepoint, and OneDrive for Business. While some services like Box expose an endpoint for listing events, others such as SharePoint and OneDrive do not. Kloudless supports these services by periodically polling them for changes, allowing you to have a consistent interface to query all the services for changes.

This short walkthrough gets you up and running with Kloudless’s Webhooks. It assumes that:

  • You already have a Kloudless account and app set up (if you don’t, you can get one here)
  • You know some Python (we will be using Flask to create a basic webserver)
  • You are familiar enough with HTTP to make/understand requests
  • You can run code somewhere accessible by the Kloudless server requests

Configuring Webhooks

The webhooks for your application can be configured on the Application Details page of the developer dashboard. All you have to do is add the URL that you would like Kloudless to make requests to. Note: before the webhook is saved, Kloudless makes a test request to it to ensure that it works, so if your application isn’t up and running yet, you won’t be able to create the webhooks.

Webhooks

The Structure of the Webhooks

The requests that we make for our webhooks are extremely simple. Here is the raw HTTP of an example request Kloudless might make to the above endpoint:

POST /kloudless-webhook HTTP/1.1
Host: yourapp.example.com
Content-Length: 14
Accept-Encoding: gzip, deflate, compress
Accept: */*
User-Agent: kloudless-webhook/1.0
X-Kloudless-Signature: VPl14EUveHQ7HcAvigiRZ7dmX7QLM5iD+pnXJv2XYok=
Content-Type: application/x-www-form-urlencoded

account=593652

As you can see it is a standard http form. We provide the id of the account that we have new events for. There will only be one account per notification. The primary purpose is to inform you that new events are available from the events endpoint. We also include a signature so that you can verify that the event actually came from our service.

Our service expects a 200 OK, with the response body consisting of only your Kloudless Application ID (available on the Developer Portal’s App Details page).

A Simple WebHooks Receiver

Using Flask we can quickly build a simple web server that can receive these notifications, retrieve the corresponding events, and do something interesting. For an extremely simple server you can use for testing purposes, check out this Gist.

Here, we will describe a more useful receiver that verifies the webhook sender and launches a task. We start with the event receiver:

#!/usr/bin/env python
from flask import Flask, request, abort

import hmac
import base64
import hashlib
import threading

app = Flask('demo_app')
APP_ID = ''
API_KEY = ''
@app.route('/webhook', methods=['POST'])
def receiver():
    # Verify the Request Signature
    digest = hmac.new(API_KEY, msg=request.data, 
                      digestmod=hashlib.sha256).digest()
    sig = base64.b64encode(digest)
    if not sig == request.headers.get('X-Kloudless-Signature'):
        abort(403)

    # Since the request is verified we can actually do something
    account_id = request.form.get('account')
    if account_id:
        threading.Thread(target=process_account, args=(account_id,)).start()

    # In order to verify that the endpoint is alive you should always return
    # your application id with a 200 OK response
    return APP_ID

if __name__ == 'main':
    app.run()

This basic structure allows you to insert just about any functionality into the process_account function. So that you don’t fetch the same events over and over again, you will have to keep track of where you are in the event stream for each account. Each time you make a request to the events endpoint you get back a cursor value that marks your current place. To track our current progress through the event stream, we are going to store the cursors for each account id in [redis])(http://redis.io). You could use your preferred data store, but redis is simple and quick to get started with. If you want to fetch new events and then process added files, write a function similar to the following (this uses python requests so that it is easier to translate to other languages):

import requests
import redis

redis_client = redis.StrictRedis(host='localhost', port=6379, db=0)

def process_account(account_id):
    # if there is an existing cursor we want to make sure we use it
    cursor = redis_client.get(account_id)
    params = {"cursor": cursor}
    headers = {"Authorization": "ApiKey %s" % API_KEY}
    url = "https://api.kloudless.com/v1/accounts/%s/events" % account_id
    response = requests.get(url, headers=headers, params=params)

    if response.ok:
        data = response.json()
        events = data['objects']
        new_cursor = data['cursor']
        for event in events:
            if event['type'] == 'add': # Only care about new/modified files
                do_something_cool(event['metadata']['id'])
        # updating cursor in datastore
        redis_client.set(account_id, new_cursor)

def do_something_cool(file_id):
    print "There is a new file: %s" % file_id

In this case, you would put your interesting functionality in the do_something_cool function. For example, you could do some sort of document conversion or content auditing with the file id that you get. The event contains the full file metadata so you can make other decisions about what to do based on extension, parent folder, or mime-type.

Best Practices

There are a few things that should be done to ensure that your Kloudless Webhooks integration works as well as possible.

Handle WebHooks Quickly

The initial handling of the webhooks requests should be done as quickly as possible. Otherwise, a high volume of requests could easily overwhelm a naive implementation that does a large amount of work prior to sending a response to the webhook requests.

Manage Concurrency

When there are lots of changes occurring for a particular account, a large number of notifications could be sent to your server. Your application should make sure that this doesn’t cause problems. For certain types of applications, the duplicate actions would not cause any issues. However, if you have non-idempotent actions or actions that are particularly expensive in terms of computation time, then make sure there is locking, leasing, or mutual exclusion for that user for the duration of the action. This ensures that duplicate work isn’t being done while the action is running.

There are other design practices for event-driven applications, but they are beyond the scope of this post.

Conclusions

Hopefully this will have provided you with a good introduction to how to take advantage of Kloudless Webhooks so that you can build more effective event-driven applications around your user’s cloud storage. Please email support@kloudless.com or chat with us on Stack Overflow if you have any feedback, questions, or insights about building your application with Kloudless Webhooks.

Send Documents on Feature Phones with Twilio and Kloudless

Hey hey! Following an intense month of events, I got inspired by all the cool hacks at Hack(bright) for Good, companies at TechCrunch Disrupt and developers at Kloud Kantina.

I thought txt.us, a WhatsApp for feature phones (find their project source code here), was especially cool, so I wanted to see if I could take the idea one step further: the ability to send files via SMS using a link.

txt_us_hackbrightforgood_2014

Team txt.us presenting at #hackbrightforgood

[tl;dr check out the finished Twilio + Kloudless project and the source code on GitHub to see an app that lets you send files stored in the cloud via SMS]

The Code

The application provides the following commands, which are sent via SMS to the application’s Twilio phone number:

  • ls – returns indexed list of visible folders
  • cd (<index>|..) – change to listed directory or to parent respectively
  • get <index> – Get an SMS with a link to download the file
  • send <index> <phone number> – send an SMS with link to file to number (e.g. +15555555555)
  • reset – starts your session back from the beginning

It is built using the Flask application that you created by the end of the Twilio SMS and MMS Python Quickstart. I had to add a bit of extra code to make it useable as a public web application, but the main cloud storage code interaction code is in the handler.py file. There I made the following translations from what I wanted into the Kloudless Python SDK code:

  • ls for accounts: kloudless.Account.all()
    this will list all accounts that your application has access to

    • In the final product, I end up storing account ID’s with phone numbers so that not every phone number sees every account.
    • To look up an individual account, you can simply do kloudless.Account.retrieve(account_id) where account_id is the id number of the account you want.
  • ls for a directory, if you have the right account object in account and the folder id in folder_id: account.folders(id=folder_id).contents()
    • To list the contents of the root folder for a particular account (with the account object stored in account): account.folders().contents() this works because the id defaults to the root directory of the cloud storage account.
  • get if you have the file object stored in file_obj and the account in account: account.links.create(file_id=file.id)
    • This returns a link object containing a url that the user can visit to preview (if the source supports it) or download the file.
    • I decided to just return a link, since I wasn’t sure whether all file types could be sent via MMS and most phones have some kind of web browser (though it might be fairly bare bones)
  • send is basically like get except that you are sending it to someone else so you have to make an extra Twilio API call

Once the basic commands were mapped out, it was relatively simple to wrap the functionality in an object that we can easily re-use.

The Twilio functionality I used was also very straight forward. For handling web hook responses, I simply create a TWiML response like so:

resp = twilio.twiml.Response()
resp.message("This should be the response from the command handler")

This can be returned to the Twilio webhook to send a response to an incoming text message. The command handler I made just outputs the message that we want to send back.

The only other functionality that I used was sending messages, which is also really straight forward:

twilio_client = TwilioRestClient(account="blah", token="blah")
twilio_client.messages.create(to="+15555555555",
                              _from="+YOURAPPNUMBER",
                              body="This is a message!")

And that is it, those are the basic pieces I used to make this app, the core parts of this application is only about 150 lines of code, the rest is just fluff to make the application more web ready (like having an actual website to log in and manage connected accounts).

Using Twilio + Kloudless

To use Twilio+Kloudless, first click the link and enter your phone number.
Check your phone for the confirmation code and enter it into the form field. Once your account is confirmed, you can connect your different cloud storage accounts via the web interface.

From your phone, text “ls” to the stated number, which then prompts you through interacting with your connected accounts. I won’t spoil all of the fun, so I’ll let you check out the project yourself.

Conclusion

Throughout this project, I didn’t have to write a single line of cloud storage service specific code, and with just those simple commands detailed above, this app works with accounts from any of the nine services supported by Kloudless.

With Twilio and Kloudless, you can use a feature phone to send files (no need for a smartphone!). Check out the code on GitHub — feel free to fork it and build your own functionality on top. If you want to get started on your own project, sign up for Twilio or Kloudless here. To bounce ideas around, leave a comment below or drop us a line at hello@kloudless.com.

Automating Development Environments with Vagrant and Puppet

Vagrant and Puppet!

Your Situation

This could be quite varied, you could be:

  1. A solo developer looking for a fast/easy way to have a local dev environment that resembles your production environment (say you develop on OS X, but are deploying to an infrastructure running some distribution of Linux. As a bonus, there is also an easy way to deploy to Amazon’s EC2 if you have a solid setup locally.
  2. A member of a team, where everyone has their own development style and want to avoid the headaches of cross-platform support.
  3. Someone who normally sets up servers in a third-party hosting environment, but you want to test your deployment without paying a bunch of money in wasted servers (this is where I am!)

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