PyChromeless

Python (selenium) Lambda Chromium Automation

PyChromeless allows to automate actions to any webpage from AWS Lambda. The aim of this project is to provide the scaffolding for future robot implementations.

But... how?

All the process is explained here. Technologies used are:

• Python 3.6
• Selenium
• Chrome driver
• Small chromium binary

Requirements

Install docker and dependencies:

• make fetch-dependencies
• Installing Docker
• Installing Docker compose

Working locally

To make local development easy, you can use the included docker-compose. Have a look at the example in lambda_function.py: it looks up “21 buttons” on Google and prints the first result.

Run it with: make docker-run

Downloading files

If your goal is to use selenium to download files instead of just scraping content from web pages, then you will need to specify a download_dir when initializing the WebDriverWrapper. Your download location should be a writable Lambda directory such as /tmp. For example, the first code in lambda_handler would become

driver = WebDriverWrapper(download_location='/tmp')

This will cause file downloads to automatically download into the download_location without requiring a confirmation dialog. You might need to sleep the handler until the file is downloaded since this occurs asynchronously.

In order to download a file from a link that opens in a new tab (i.e. target='_blank') you will need to call enable_download_in_headless_chrome in your scraping script after navigating to the desired page, but before clicking to download. This will replace all target='_blank' with target='_self'. For example:

# Navigate to download page
driver._driver.find_element_by_xpath('//a[@href="/downloads/"]').click()
# Enable headless chrome file download
driver.enable_download_in_headless_chrome()
# Click the download link
driver._driver.find_element_by_class_name("btn").click()

Building and uploading the distributable package

Everything is summarized into a simple Makefile so use:

• make build-lambda-package
• Upload the build.zip resulting file to your AWS Lambda function
• Set Lambda environment variables (same values as in docker-compose.yml)
  • PYTHONPATH=/var/task/src:/var/task/lib
  • PATH=/var/task/bin
• Adjust lambda function parameters to match your necessities, for the given example:
  • Timeout: +10 seconds
  • Memory: + 250MB

Shouts to

• Docker lambda
• Lambdium
• Serverless Chrome repo & medium post
• Chromeless

Contributors

• Jairo Vadillo (@jairovadillo)
• Pere Giro ()
• Ricard Falcó (@ricardfp)