chromewhip 0.2.2

asyncio driver + HTTP server for Chrome devtools protocol

Chrome browser as an HTTP service with an splash compatible HTTP API

Chromewhip is an easily deployable service that runs headless Chrome process wrapped with an HTTP API. Inspired by the `splash <https://github.com/scrapinghub/splash>`__ project, we aim to provide a drop-in replacement for the splash service by adhering to their documented API.

It is currently in early alpha and still being heavily developed. Please use the issue tracker to track the progress towards beta. For now, the required milestone can be summarised as implementing the entire Splash API.

Python 3.6 asyncio driver for Chrome devtools protocol

Chromewhip communicates with the Chrome process with our own asyncio driver.

• Typed Python bindings for devtools protocol through templated generation - get autocomplete with your code editor.

• Can bind events to concurrent commands, which is required for providing a robust HTTP service.

Some example code on how to use it:

import asyncio
import logging

from chromewhip import Chrome
from chromewhip.protocol import page, dom

# see logging from chromewhip
logging.basicConfig(level=logging.DEBUG)

HOST = '127.0.0.1'
PORT = 9222

loop = asyncio.get_event_loop()
c = Chrome(host=HOST, port=PORT)

loop.run_until_complete(c.connect())

tab = c.tabs[0]

loop.run_until_complete(tab.enable_page_events())

cmd = page.Page.navigate(url='http://nzherald.co.nz')

# send_command will return once the frameStoppedLoading event is received THAT matches
# the frameId that it is in the returned command payload.
await_on_event_type = page.FrameStoppedLoadingEvent

result = loop.run_until_complete(tab.send_command(cmd, await_on_event_type=await_on_event_type))

# send_command always returns a dict with keys `ack` and `event`
# `ack` contains the payload on response of a command
# `event` contains the payload of the awaited event if `await_on_event_type` is provided
ack = result['ack']['result']
event = result['event']
assert ack['frameId'] == event.frameId

cmd = page.Page.setDeviceMetricsOverride(width=800,
                                         height=600,
                                         deviceScaleFactor=0.0,
                                         mobile=False,
                                         fitWindow=False)

loop.run_until_complete(tab.send_command(cmd))

result = loop.run_until_complete(tab.send_command(dom.DOM.getDocument()))

dom_obj = result['ack']['result']['root']

# Python types are determined by the `types` fields in the JSON reference for the
# devtools protocol, and `send_command` will convert if possible.
assert isinstance(dom_obj, dom.Node)

print(dom_obj.nodeId)
print(dom_obj.nodeName)

Running

Deploying with Docker

docker run --init -it --rm --shm-size=1024m -p=127.0.0.1:8080:8080 --cap-add=SYS_ADMIN \
  chuckus/chromewhip

Requirements for MacOS 10.12+

• Google Chrome Canary

Implemented HTTP API

/render.html

Query params:

• url : string : required

• The url to render (required)

• js : string : optional Javascript profile name.

• js_source : string : optional

• JavaScript code to be executed in page context

• viewport : string : optional

• View width and height (in pixels) of the browser viewport to render the web page. Format is “x”, e.g. 800x600. Default value is 1024x768.

  ‘viewport’ parameter is more important for PNG and JPEG rendering; it is supported for all rendering endpoints because javascript code execution can depend on viewport size.

/render.png

Query params (including render.html):

• render_all : int : optional

• Possible values are 1 and 0. When render_all=1, extend the viewport to include the whole webpage (possibly very tall) before rendering.

Why not just use Selenium?

• chromewhip uses the devtools protocol instead of the json wire protocol, where the devtools protocol has greater flexibility, especially when it comes to subscribing to granular events from the browser.

Bug reports and requests

Please simply file one using the Github tracker

Contributing

Please :)

Implementation

Developed to run on Python 3.6, it leverages both aiohttp and asyncio for the implementation of the asynchronous HTTP server that wraps chrome.