This is a simple price monitor built with Scrapy and Scrapy Cloud.

It is basically a Scrapy project with one spider for each online retailer that we want to monitor prices from. In addition to the spiders, there's a Python Script that is scheduled to run periodically on Scrapy Cloud, checking whether the latest prices are the best ones in a given time span. If so, the monitor sends an email alerting you about the price drops.

There's a resources/urls.json file that lists the URLs from the products that we want to monitor. If you just want to include a new product to monitor from the already supported retailers, just add a new key for that product and add the URL list as its value, such as:

{
    "headsetlogitech": [
        "https://www.amazon.com/.../B005GTO07O/",
        "http:https://www.bestbuy.com/.../3436118.p",
        "http:https://www.ebay.com/.../110985874014"
    ],
    "NewProduct": [
        "http:https://url.for.retailer.x",
        "http:https://url.for.retailer.y",
        "http:https://url.for.retailer.z"
    ]
}

This project currently only works with 3 online retailers, and you can list them running:

$ scrapy list
amazon.com
bestbuy.com
ebay.com

If the retailer that you want to monitor is not yet supported, just create a spider to handle the product pages from it. To include a spider for samsclub.com, you could run:

$ scrapy genspider samsclub.com samsclub.com

And then, open the spider and add the extraction rules:

$ scrapy edit samsclub.com

Have a look at the current spiders and implement the new ones using the same structure, subclassing BaseSpider instead of scrapy.Spider. This way, your spiders will automatically read the URLs list from resources/urls.json.

The price monitor sends an email using Amazon SES service, so to run it you have to set both AWS_ACCESS_KEY and AWS_SECRET_KEY variables in price_monitor/settings.py. If you want to use another email service, you have to rewrite the send_email_alert function in price_monitor/bin/monitor.py.

The price monitor can be further customized via parameters to the price_monitor/bin/monitor.py script. We will dig on those parameters later when showing how to schedule the project on Scrapy Cloud.

1. Clone this repo:

    $ git clone [email protected]:stummjr/scrapy_price_monitor.git
   

2. Enter the folder and install the project dependencies:

    $ cd scrapy_price_monitor
    $ pip install -r requirements.txt
   

3. Create a free forever account on Scrapy Cloud: https://app.scrapinghub.com/account/signup/.

4. Create a Scrapy project on Scrapy Cloud and copy the project id from the project URL.

5. Install Scrapinghub command line tool (shub):

    $ pip install shub
   

6. Authenticate using your Scrapinghub API key:

    $ shub login
   

7. Finally, deploy the local project to your Scrapy Cloud project:

    $ shub deploy <your_project_id_here>
   

This video also explains how to deploy a Scrapy project to Scrapy Cloud: https://youtu.be/JYch0zRmcgU

After you have deployed the project to Scrapy Cloud, it's time to schedule its execution on Scrapy Cloud.

This project has two main components:

• the spiders that collect prices from the retailers' websites
• the price monitor script that checks whether there's a new deal in the latest prices

You have to schedule both the spiders and the monitor to run periodically on Scrapy Cloud. It's a good idea to schedule all the spiders to run at the same time and schedule the monitor to run about 15 minutes after the spiders.

Take a look at this video to learn how to schedule periodic jobs on Scrapy Cloud: https://youtu.be/JYch0zRmcgU?t=1m51s

The monitor script takes these parameters and you can pass them via the parameters box in the scheduling dialog:

• --days: how many days of data we want to compare with the scraped prices.
• --threshold: a margin that you can set to avoid getting alerts from minor price changes. For example, if you set it to 1.0, you will only get alerts when the price drop is bigger than $1.00.
• --apikey: your Scrapy Cloud API key. You can get it in: https://app.scrapinghub.com/account/apikey.
• --project: the Scrapy Cloud project where the monitor is deployed (you can grab it from your project URL at Scrapy Cloud).

You can run this project on Scrapy Cloud or on your local environment. The only dependency from Scrapy Cloud is the Collections API, but the spiders and the monitor can be executed locally.

To do that, first add your Scrapy Cloud project id to settings.py SHUB_PROJ_ID variable.

Then run the spiders via command line:

$ scrapy crawl bestbuy.com

This will run the spider named as bestbuy.com and store the scraped data into a Scrapy Cloud collection, under the project you set in the last step.

You can also run the price monitor via command line:

$ python bin/monitor.py --apikey <SCRAPINGHUB_KEY> --days 2 --threshold 1 --project <PROJ_ID>